Servicing &amp
Servicing &Technology
SEPTEMBER 1982/$2.25
Average or true RMS: Which is right for you?
Maurice Brinegar
Module Operations Manager,
Bloomington
Depend on the
quality "We Care"
inspection your
tuners and
modules get at
PTS.
At PTS, service is our only
business. So, in quality control each
module and tuner we inspect gets
"We Care" attention before we ship
it to you.
When we're servicing your tuners
and modules you can be assured of
a thorough inspection.
Each
module and tuner is sent through a
nine -step rebuilding cycle of which
four steps are quality control inspection.
It's just part of our commitment to
quality and serving you.
Only one company has the "We
Care" spirit in quality inspection.
Only One.
PTS CORPORATION
For the name of the PTS Distributor or Servicenter nearest you write PTS Corporation, P.O. Box 272, Bloomington, IN 47402
Circle
(1)
on Reply Card
EI9OTR011ie
Editorial, advertising and circulation correspondence should be addressed to: P.O. Box
12901, Overland Park, KS 66212-9981 (a suburb
of Kansas City. MO); (913) 888-4664.
EDITORIAL
Bill Rhodes, Editorial Director
Nils Conrad Persson, Editor
Carl Babcoke, Consumer Servicing Consultant
Rhonda Wickham, Managing Editor
Tina Thorpe, Associate Editor
ART
Kevin Callahan, Art Director
Kim Nettie, Graphic Designer
CIRCULATION
John C. Arnst, Director
Evelyn Rogers, Manager
Dee Manies, Reader Correspondent
Hancock, President
Cameron Bishop, Publisher
R. J.
ADVERTISING
Greg Garrison, National Sales Manager
Jean Jones, Production Manager
Mark Raduziner, Marketing Coordinator
Member, Audit Bureau
of Circulation
Member, American
Business Press
ELECTRONIC SERVICING & TECHNOLOGY (USPS 462-050)
(with which is combined Electronic Technician/Dealer) is
published monthly by Intertec Publishing Corp., 9221
Ouivira
Road,
P.O.
Box
12901, Overland Park,
each function. Applications are virtually
unlimited. It "displays" a standard digital readout,
an audible tone for rapid overt under checks and
an over/under arrow.
Unique 128 design enables you t
verify forward conduction and reverse
tz
blocking of semiconducr
check
testtion
LEDs arilompoeents
.
c
ur
Sour,junctiorsmultiplej,
Even with the beeps: on, the
128 maintains 10Mil in-Jut re. You can caibriate>Ie
beeper thresho_d
and the A/D without disassemblirg the instrument.
The 128 is human engineered
with a large, 0.6" display, rugged
ABS case and display window,
35O-hr battery life and overload
protection.
Much less versatility can cost
much more than $139.
The 128 is the sound choice
because it's the smart buy.
Contact your local Keithley representative or distributor.
iiifor
e
d
COice.sibstancet
ADMINISTRATION
ABP
Our new model 128 has a beeper and a whole lot more.
After you've seen it we think youll agree that this is the
best all around field service DMM available. It beets
on all three functions-V Sl and A-and on all ranges
KS
66212-9981. Second Class Postage paid at Shawnee Mission, KS 66201. Send Form 3579 to P.O. Box 12952,
Overland Park, KS 66212-9981.
ELECTRONIC SERVICING & TECHNOLOGY is the "how-to"
magazine of electronics. It is edited for electronic profes-
sionals and enthusiasts who are interested in buying.
building, installing and repairing home-entertainment electronic equipment (audio, video, microcomputers, electronic
games, etc.).
KEITH LEY
Keithlev Instruments, Inc.
28775 Aurora Road/Cleveland, OH 44139
(216) 248-0400 Telex: 98-5469
SUBSCRIPTION PRICES: one year $15, two years $26,
three years $34 in the USA and its possessions. Foreign
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Allow 6 to 8 weeks for new subscriptions.
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01970. Special requests should be addressed to Cameron
Bishop, publisher.
ISSN 0278-9922
INTERTEC PUBLISHING CORP.
1982 All rights reserved.
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September 1982
Electronic Servicing & Technology
3
The how-to magazine
of electronics...
EIEGTROAiO
September 1982
Volume 2, No. 9
10
s
Reports from the test lab:
The Thomas 4754 talking DMM
By Carl Babcoke, CET
This DMM announces the reading on the LCD display in
ELECTYiiOBiC
understandable English.
14
Sams offers a cure for your
troubleshooting symptoms
Quickfacts is the result of a national survey to determine
the needs of electronics service technicians.
16
By Bernard Daien
The Schmitt trigger can be used as a switching contact
debouncer, for signal conditioning, as a level detector, and
in control systems to prevent hunting.
Digital multimeters are
changing to meet the growth
of electronic technology. See
story on page 46. (Photo
courtesy of Simpson. Electric.)
Digital building blocks: The Schmitt trigger
26
Servicing conduction -time regulation
By Homer L. Davidson
The B + regulation in some J.C. Penney models requires
different diagnostic procedures than other regulators.
46
A
reading on the DMM market
With more consumer electronic products featuring digital
circuitry, it has become necessary for manufacturers to
provide the means with which to measure these circuits.
56
Previewing the GE 1983 line
By Carl Babcoke, CET
Large and small screens, portability and new circuitry are
features of General Electric's new line of video and television.
66
Average or true RMS: Which is right for you?
By Jim Smith, Sencore
There are good reasons for both of these measurements,
depending on the situation and the information needed.
4
Electronic Servicing
&
Technology
September 1982
Departments
6
Editorial
6
Feedback
8
Electronic Scanner
8 Association News
35 Troubleshooting Tips
36 Symcure
Page 26
45 Books
65 Calendar of
Events
68 New Products
72
Readers' Exchange
Page 46
Next month...
Profax. Readers
have asked for TV E5
schematics, similar to those in- schematics
eluded in Electronic Technician/Dealer, and they will begin in the October
issue. Each issue will include an 8 -page pull-out of comprehensive schematics from major TV manufacturers, which can be
filed away for future reference.
ManufacturersPilloonH
Page 56
September 1982
Electronic Servicing & Technology
5
EDITORIAL
Technological growth demands adaptability
In Time magazine, the issue of the week of July
there was an article on the last page
that discussed the attitudes of executives to
computers. It revealed an incredible resistance on
the part of people who would normally be
expected to be very flexible in accepting new and
unfamiliar equipment.
For example, the article described a financial
executive in a U.S. firm who insists that all
reports that he reads be typed on plain white
paper. He says he simply will not trust anything
he reads on green and white striped computer
12, 1982,
printout paper.
The article goes on to discuss the fact that in
spite of the savings in time and effort that might
be netted by an executive who used a personal
computer, or a terminal in his office, it's rare to
see one on an executive's desk.
The article concludes with the suggestion that
younger people, who are growing up with
computers, will probably bring computers with
them when they move into the executive suite.
Humans are among the most adaptable animals
on earth (perhaps outdone in adaptability only by
the shark, the cockroach and a handful of other
creatures), able to exist in desert or rainforest,
mountains or seacoast, tropical heat or artic cold.
But as evidenced by the executives' reticence when
faced by computers, when man's own technology
begins to develop too rapidly and becomes too
complex, that ability to adapt begins to falter.
Nowhere, today, is the pace of change more
rapid than in the area of electronics. The problems
surrounding the computer have already been
alluded to here. But that's only part of the story.
Other rapid developments are forcing all of us,
like Alice in Wonderland, to run ever faster just to
Stereo amplifier repair
I read with great interest the
article by Carl Babcoke in the
April issue, "Stereo amplifier
repair," and wish you would include more articles concerning
audio servicing, as there is very
sophisticated hi-fi equipment in
need of servicing, and when the
price of equipment is taken into
consideration, very profitable
repairs could be made.
6
Electronic Servicing & Technology
stay in the same place. In fact it sometimes seems
that no matter how hard we run, the current pace
of change in electronics is going to leave us
panting in the dust.
As an example, digital circuitry is being
introduced in to all manner of equipment from
television and radio to sophisticated industrial
equipment. And more digital is coming.
Commercial availability of compact digital
recordings is a year or two away. Yet most of us
still think analog. How many servicers know how
to use a logic probe, or a logic analyzer?
Most electronic servicers must have made the
commitment at some point in their careers to
continue learning-that has always been the
nature of a dynamic technology like electronics.
Now that electronics is changing more rapidly
than ever, the time is here to reaffirm that
commitment, not abandon it.
Manufacturers' schematics
to be added to ES&T
Since we brought up the subject of commitment,
let us (ES&T) reaffirm our commitment to
provide readers with the kind of information they
need. Beginning with our October issue, we will be
including eight pages of manufacturer's schematics
and service data. This new pull-out section, entitled
"Profax," will provide easy reference roadmaps for
your servicing needs. To long-time ES&T
subscribers this will be a new service that's sure to
make ES&T more valuable. To those subscribers
who came to use from ETID it's a reinstatement of
the kind of schematics that ETID used to run, back
byy popular demand.
I do have one question, or rather
one comment, to make concerning
the test "hook-up" of the dummy
load resistor, capacitor and series
resistor with the test speaker
paralleling that 89 load resistor.
No mention was made of impe-
dance -matching considerations,
and it has always been my practice, especially when servicing
OTL circuits, to always terminate
with this thought in mind. So I am
wondering if this was done, or if
under the circumstances of reduced line voltage this is not
necessary. I would appreciate a
comment, however brief it is.
I also realize that it is not possible to cover everything in a short
September 1982
article and that it must be assumed the readers have some
knowledge of theory, and while
this in no way should be taken as
any criticism, it has me somewhat
puzzled. I guess we all find
ourselves bothered by small insignificant things at times.
Thomas Hurley
Montara, CA
Reply
Impedance matching between
amplifier output and a load, such
as a speaker, is desirable for
several reasons. In general,
matching impedances of any
source and its load provides max -
imum transfer of power to the
load. Amplifier power is expensive
and should not be wasted by
mismatching. With transistor
amplifiers, the situation is more
complicated. A 452 load on the 852
output of an amplifier provides
higher -than -normal wattage, but
at increased distortion. A 1652
load on the same 852 output will
receive decreased power, but the
distortion is the same or lower.
Amplifier matching is not a precise
science.
Also, the value of the amplifier
load often affects stability and frequency response. When the load
has several times the correct impedance or is open, a poorly
designed amplifier might become a
generator of a full -power inaudible
supersonic signal that could
destroy the output transistors. A
scope is needed here. Other inade-
quate amplifiers might motorboat
or develop excessive distortion
when load impedance is too high.
Low -impedance loads produce
other problems. The output wattage and negative feedback are
reduced. If attempts are made to
restore the lost volume by turning
up the gain control, the dissipation
rating of the output transistors is
exceeded and a sudden catastrophic failure is very likely.
Remember also that speakers
never have a constant impedance
over the frequency range. In
general, the impedance rises
somewhat with frequencies higher
than 400Hz, and a definite large
increase of impedance occurs at
the natural cone -resonant frequency. For example, an 852 speaker
might have minimum impedance
of 72 at 300Hz or 400Hz, rising to
1552 at 10kHz, and showing a 4052
peak at the 70Hz resonant point.
How should such a speaker be
matched? Often, the impedance at
400Hz is used as the speaker impedance rating.
Returning to your question
about amplifier-output matching
of the dummy load in the April
ES&T article, beginning on page
12, the matching is not so incorrect as you assumed. Refer to the
Figure 4 schematic on page 16.
The major load is the 852 non inductive power resistor. Paralleling it are the speaker, a 10µF
capacitor and a 2752 resistor in
series. At 400Hz, the 10µF
capacitor has a capacitive reactance of 39.852. The sum of these
three components, therefore, is 27
+ 39.8 + 8, or a total of 74.852. At
extreme high frequencies the sum
is about 4052, and in the bass range
the impedance is several hundred
ohms (which can be neglected).
When 74.852 is paralleled across
the 852 load, the resulting impedance becomes 7.2352.
Therefore, the reduction of
right-channel output load was insignificant at middle and bass frequencies. No mismatching danger
was produced by this speaker protecting test circuit, particularly
since the volume never was
operated for maximum undistorted output at any time.
Carl Babcoke
Customer Servicing Consultant.
Me,
You'll find
MORE
in wiring components at a
Sprague Q -LINE Distributor
Look for the Q -LINE wiring component display. You'll find exactly what
you want in solderless terminals and wiring component accessories ..
shrink tubing, cable ties, cable clamps, terminal blocks, butt connectors,
bullet connectors, quick -splices, end caps, soldering aids, wiring tools,
and component assortments. Everything
is logically arranged for quick location.
Q-MART
.
5
ORdNG
QdJNE
WIRING COMPONENTS
a<^<<uF,s
eos
JUST ONE OF
DOZENS
THAT CAN
OF PRODUCTS
SAVE YOU
TIME EVERY
DAY.
,..:'=ii.=Ì
.,;
POCKET
IYPAIÇTM: Here's
convenience plus/
caddy and pocketCombination tie
comes prefilled saver. One side
assorted colors. with 30 ties in 5
Other side is
pocket-saver pouch
a
for pens,
pencils, rules,
etc.
For detailed information on all Q -LINE products (capacitors, switches, chassis
boxes, optoelectronic devices, DIP/SIP components, resistors, wiring components, etc.) writefor 40 -page Catalog C-652 to Sprague Products Co., Distributors'
Division of the Sprague Electric Co., 65 Marshall St.,
5507,
North Adams, Mass. 01247.
SPRAGUE.
Where MORE is more than a promise.
THE MARK OF RELIABILITY
a
Circle
(5) on Reply
September 1982
subsidiary of OK
Technologies
Card
Electronic Servicing
&
Technology
7
Biddle Instruments, 510 Township
Line Road, Blue Bell, PA 19422;
1-215-646-9200.
ELECTRONIC
SCANNER
ICS offers course on
Biddle Instruments offers
technical courses
Biddle Instruments will offer a
selection of technical courses for
fall at their school in Jenkintown,
PA.
"Earth Resistance Testing" will
be offered Sept. 2-3; "Power-Cable
Fault Location" will be taught
Sept. 20-23; "Partial Discharge
(Corona) Detection in Insulation
Systems" will be held Oct. 25-29
and "dc Testing of Power Apparatus Insulation" is scheduled
for Nov. 15-18.
For more information, contact
ASSOCIATION
NEWS
NATESA suggests use
of satellites in training
The National Television & Electronic Servicers of America
(NATE SA) organization has released this announcement:
"In an industry such as consumer
electronics, where major technological changes occur so often,
prompt training to enable efficient
service operations is essential.
"We recognize problems of set
producer/marketers in bringing
prompt training sessions to all servicers quickly. The problem of
training distributor people, who
then are to train servicers in their
area, calls for large numbers of
trainees of servicers. It calls for
authorized warranty servicers to
travel considerable distances and
it delays training of independent
servicers.
"We believe the cost of training in
8
Electronic Servicing & Technology
microprocessor troubleshooting
Integrated Computer Systems is
offering a course entitled "Hands On Microprocessor Troubleshooting" that provides participants
with the opportunity to learn practical troubleshooting techniques.
These techniques are reinforced by
in -class training with test equipment specifically intended for
microprocessor applications.
The course, priced at $895, will
be held in Boston Oct. 5-8, in New
York City Nov. 2-5, in Washington, DC Dec. 14-17, and in Los
Angeles Jan. 25-28.
For more information, contact
Ruth Dordick, Integrated Computer Systems, 3304 Pico Blvd.,
time and dollars can be greatly reduced by use of satellite communications. Simultaneous sessions could be held in all parts of
the nation. This could reduce size
of training staffs and positions
becoming very hard to fill. To
make use of this new technology,
changes in training to substitute a
major degree `hands on' techniques will need to be developed.
"We are proposing to producer/
marketers that this new concept
be explored. We have explored services of this general nature and
ask for further study by EIA and
its consumer electronics service
managers."
EIA/EAC jointly support
technical education bill
The Electronic Industries Association (EIA) along with Electronic Association of California (EAC)
offered their support to a congressional bill (HR 5820) designed to
increase the supply of trained technicians in the U.S. high-technology
industry.
Testifying jointly in San Francisco before a subcommittee of the
House Committee on Education
September 1982
P.O. Box 5339, Santa Monica, CA
90405, 1-213-450-2060.
New venture to allow for
direct -to -home programming
The Aluminum Company of
America and Nippon Electric
Company of Japan have formed a
new corporation to assemble and
market TV receiver systems that
will make it possible for individual
homes and apartments to obtain
TV programming directly from
broadcast satellites.
The new company, ALCOANEC Communications Corporation will draw upon the resources
of Alcoa in the manufacture of
aluminum and NEC in the
manufacture of telecommunications equipment, computers and
semiconductors.
SSW
and Labor, James Conway, president of EAC and Gary Petersen,
vice president of human resources
for GTE and chairman of a special
manpower task force of EIA,
noted, "We are the world's leader
in technology and we must maintain that lead for economic stability and national security. We can
only do this with a solid base of
scientific and technological skills
and literacy at all levels in the
United States. HR 5820
represents an effective step in
ameliorating the serious shortage
of skilled and technical manpower
available to the high technology industries."
The pair disagreed, however,
with a small point in the legislation: its contention that "The expansion of these industries within
the United States is dependent on
their ability to attract competent
employees."
Attracting them is really not the
problem according to the industry
executives. Instead, the industries'
ability to expand is dependent on
a "trained pool of personnel
available for employment."
"Is it wishful thinking to want a
50 MHz portable scope with
1 mV/div sensitivity for under $2,000?"
HYTACHI HEARD YOU.
Not since Hitachi introduced the dual trace, delayed
sweep V-509. For only $1,895 you get a dynamic range
of 8 full divisions. Sensitivity to 1 mV/div at 10 MHz. And
sweep times down to 10 ns/div. For today's sophisticated
electronics, computers and VTRs, it's the perfect field
service tool.
Weighing a mere 11 pounds, in an 8.5" x 4.3" x
13.8" package, the V-509 is, nevertheless, a heavyweight
when it comes to performance. Auto focus, a built-in
TV sync separation circuit
and Channel 1 DVM output
are standard. There's even a
single -sweep function to
reliably measure one-time
events. Plus AC/DC operation
and an optional battery pack,
so you can take the V-509
wherever it's needed.
Hitachi's human engineering is evident in every
facet of V-509 design. Its bright, 3.5" diagonal CRT is
easy to read. Functionally grouped front-panel controls
make for fast, efficient use.
Also from Hitachi is the V-209, list price $995. A 20
MHz, dual trace, mini -portable scope with many of the
same performance and ease -of -use features as the V-509.
thinking about
purchasing a mini -portable
scope, you know who to
think of. Hitachi Denshi
So if you're
America, Ltd., 175 Crossways
Park West, Woodbury, NY 11797.
(516) 921-7200. Offices also in Chicago, Los Angeles, Atlanta, Cincinnati, Dallas, Denver, Seattle and
Washington, D.C.
Circle (6) on Reply Card
ngigDoMe qTiorg
lag lee
e,
The Thomas
4754
talking DMM
Figure 1 This digital multimeter announces in words the same reading shown by the LCD display. The 31/2 -digit DMM has a speech synthesizer with a vocabulary of more than 14 words. The external
transformer (shown here) provides ac operation, or five hours of
operation can be obtained from the internal NiCd batteries after
each charging.
Each report about an item of electronic test equipment is based on
examination and operation of the
device in the ES&T laboratory.
Personal observations about the
performance and details of new
and useful features are spotlighted,
along with tips about using the
equipment for best results.
Talking digital multimeter
Talking toys, video games and
computers are no longer news.
Digital multimeters often have an
audio tone that varies in frequency
according to the relative reading.
However, the Arthur M. Thomas
Company model 4754 is the first
digital multimeter (to our
knowledge) that speaks the
reading in .understandable
English.
Thomas model 4754 (Figure 1)
appears to be a conventional
DMM. The sample examined in the
ES&T Test Lab appears to be a
pre -production sample, because
some of the panel markings are
glued to the material. There is little about the appearance of the
10
Electronic Servicing
&
Technology
By Carl Babcoke, CET
range, ± 0.25% for the 1.999K
range, and ± 0.15% for the 20K,
200K and 2000K ranges.
meter to indicate anything
Six push -buttons on the left side
unusual, although one panel mark- of the panel (Figure 2) select
ing shows 4754 TMM (which prob- resistance, ac and dc voltage, or
ably stands for talking multimeter) current measurements, and turn
and one control is labeled volume. operating power on and off. The
LCD 31/2 -digit readout is at the
Basic specifications
center, with five push -buttons on
Model 4754 is a 5 -function DMM the right of the panel for selecting
that measures ac and dc voltages, the ranges (Figure 3). Above the
ac and dc current, and resistances range buttons is a rotary control
in 22 ranges. Maximum panel marked volume. The two jacks for
markings show ranges of 0.2, 2, test probes are at the upper right
20, 200 and 2000, but the maxi- corner. Except for various idenmum readouts are one digit less. tifications, these are the only items
In addition, the ac and dc voltage on the front panel. On the back
ranges have maximum safe panel are three jacks, one each for
readings.
external power/charger, earphone
Input resistance is 10M0 for all and talking -initiation control.
ac and dc voltage ranges, which
Included with the DMM are one
have accuracies of ± 0.15% at full pair of test probes, one earphone
scale. Maximum displays are for listening to the verbal readout
1.999V, 19.99V and 199.9V for all and a transformer -type battery
but the 1999V ranges. Maximum charger. Optional accessories are a
safe input voltages are 1000Vdc or foot -operated switch and a probe
500Vac (allowing for the peak with switch for activating the verbal speech on command.
voltages).
The accuracy of each current
range is different from the others.
Talking readouts
Accuracies of the dc and ac curUnderstandable synthesized
rent ranges are ± 0.5% for the English words corresponding to
0.1999mA ranges, ± 0.15% for the the digital readout are heard
1.999mA ranges, ± 0.25% for the automatically when the volume
19.99mA ranges, ± 0.75% for control is turned up. Unless the opthe 199.9mA ranges and ± 2.5% tional speech -control switch is acfor the 1999mA ranges.
tivated, the digital reading freezes
Rated accuracy is ± 0.50% for and the talking words are heard
the 0.1999K (199.9n) resistance about once per seven seconds.
September 1982
Panasonic has just
put Seattle on its map
CHICAGO
Midwest Region
425 East Algonquin Road
Arlington Heights, Illinois 60005
(312) 364-7933
SEATTLE
National Distribution
Center
SECAUCUS
Northeast Region
50 Meadowland Parkway
Box 1562
Secaucus, N.J. 07094
(201) 348-7500
P.O.
LOS ANGELES
ATLANTA
Western Region
2121 Yates Avenue
City of Commerce, Calif. 9004
(213) 723-6271
Southeast Region
2 Meca Way
Norcross, Georgia 30093
(404) 923-2500
DALLAS
South Central Region
1825 Walnut Hill Lane
Irving, TX 75062
(214) 258-0716
Faster. Better. That's the Panasonic
Consumer Parts Division's new national
distribution system. Thanks to a new parts
distribution center and two new computer controlled storage and retrieval systems,
we've substantially reduced the time
needed to process parts orders for
regional distribution.
This new system complements the
improvements already made in our
computerized distribution network:
Automatic drop shipment from any one of our
five regional depots regardless of where the
order originates from
Automatic substitutions
Automatic replenishment of regional stocks
On line status information
Panafax facsimile network linking the
regional depots together
The overall result is a binding together of
our resources in order to service you
better. In addition we have:
A central parts depot with 170,000 individual
parts on file and in addition five regional parts
depots with 25,000 part numbers in stock
Toll free calls connect Panasonic distributors
and authorized servicenters to automatic
facsimile machines located at regional parts
depots, allowing us to receive orders 24 hours
a day, 7 days a week.
One hundred independent part distributors
conveniently located to bring needed parts and
accessories closer to the customer
Plus a toll free number (800-447-47001 for
the location of the nearest authorized Panasonic
parts distributor. Except for Illinois:
(800-322-44001
Our system is designed to get parts to a
customer more quickly and easily than
ever before. At Panasonic, we never stop
trying to think of ways to better serve our
customers.
Panasonic,
of our
just slightly ahead
time
good reasons
1 RCA SK Devices
More and more electronic technician
dealers are reaching for reliable RCA solid state
replacements ... the line of integrity,
with unsurpassed engineering excellence. Our warranty return
rate is less than 0.5%, which
helps reduce costly service
call-backs. And SK devices
are readily available, to
help you do more jobs,
more profitably.
TS
r
MA
PWR`DCLAC`DC AC/Kí2
Figure 2 Six push -buttons on the panel at the left select five functions and control the power on/off. The LCD readout is at the
center of the panel.
When the control switch is turned
on, the frozen display and the
vocal readout occur almost instantly and continues to repeat until the switch is turned off. A
momentary pressure on the switch
produces one complete readout,
then the voice is heard every seven
seconds, unless activated by the
control switch again.
12
Electronic Servicing & Technology
Figure 3 Five push -buttons at the right on the panel select ranges.
Volume control for the audible readout is above the buttons. Turning down the volume control eliminates the audible words. An earphone can be used in noisy locations to provide private loud and
clear talking readouts.
The synthesized voice has an unemotional quality with a hint of
buzz in it, as though made by
modulated hum. However, it is
completely understandable, even
when heard for the first time. For
noisy locations, or when privacy is
desired, an earphone can be
September 1982
plugged in the rear panel to provide loud, clear sounds with a
minimum of environmental noise.
A single word is provided for
each item on the LCD reading, including the four 7 -segment digits,
the positive sign, the negative sign
and the decimal.
to reach for reliability.
RCA SK Series
2. Replacement Guidee
It's the book to turn to for top -performing transistors, rectifiers, thyristors, high voltage multipliers and integrated circuits. 1800
SK and KH types let you make over 178,000 solid
state replacements.
That's interchangeability. The
guide features a
convenient, dual numbering systemincluding REN,
ECG and TM
systems in
corresponding
SK numbers
where applicable.
3
RCAs latest
SK SKoop
Get all the latest news and service
updates in the SK SKoop newsletter. Published
periodically, it keeps you in tune with any
changes in the RCA SK lineup, including
product additions, deletions and modifications. The SK SKoop is full of handy
service tips, technical information and
helpful application advice. It's yours
free, and right at your fingertips. Pick
up your copy from the counter
display at your local RCA
SK Distributor.
With dealer support like
this, it makes sense to visit your
RCA SK Distributor and reach
for reliability.
RCAsK
Replace
Solid State
RCA Distributor and Special Products Division, Deptford, N.J. 08096
Figure 4 An arrow points to a 64 -pin IC that
probably contains the speech synthesizer.
Additionally, 4 small ICs and 5 medium-sized
ICs are included. The round white circle
below the center is the magnet of a small
speaker that speaks through the cases's bottom. Notice the absence of shielding, which
might allow external radiations to affect
some readings in certain environments.
The minus and plus words are
used only with dc voltage and cur-
rent. They do not appear on other
functions because the readout does
not show any polarity. Only those
things that appear on the LCD
readout are verbal.
When measuring a resistor, the
LCD readout might show 2.92
when the 20K button is pressed,
and the voice says, "Two point nine
two." (However, the nine sounds
very much like times.) The
operator must keep in mind that
the announced resistance reading
is always in thousands (k).
Any overrange, including open
test probes during resistance
measurements, produces an LCD
readout of IEEE (with a decimal
according to the range selected)
and the voice constantly says,
ceivers: No electrostatic or RF
shielding is supplied inside the
plastic cabinet (Figure 4).
Of course, the unique feature of
model 4754 is the synthesized
speech that audibly announces the
same reading shown by the LCD
digital readout. This audible readout can have great value in several
situations, including making
measurements in crowded circuit
boards (where the slightest slip of
a test probe can destroy valuable
solid-state components), because
the technician can watch the test
probes constantly without being
forced to look at the DMM
readout. It is also valuable when
operating in dim light or in a location where the operator cannot see
the DMM readout, or when the
over."
over,
"Over,
technician has vision problems.
The Thomas model 4754 talking
Comments
(TMM) can be helpful
permultimeter
This model adequately
formed all the standard five func- to many technicians. To others, it
tions. There is only one omission might be indispensible.
that could cause false readings
around radio transmitters or the
high -voltage section of color re-
IOW
September 1982
Electronic Servicing & Technology
13
CTC92
RCA
RCA
CTC92
LEE
PIMPLE
LIPEO PLOW
SAMS QUICKFACTS`"
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23
SEE MODELMASSIS
AC
UNDER CONTENT*
The symptom list for a specific television directs the user to the appropriate
page.
In October of 1
är W.
Sams & Company, Indianapolis,
IN, conducted a national survey
designed to determine the desire
of electronics service technicians
to purchase a quick -repair service
hint product. The results of the
survey were design criteria that
called for a final product reflecting
the following characteristics:
simple and quick to use
portable
technically accurate
moderately priced
comprehensive
appealing to specialty shops
cross-references
photo identification of devices
organized by manufacturer
trade name
provide additional technical
data as warranted
updatable
The engineering staff set out to
embody these criteria into a new
concept of service documentation.
This product, called Quick.
14
preinal
cheeete
CRT
mar OeL...anP ...don ..0.5 M Me. 0. Occ.nny, c0.a Pet «Pion for them.«
..M.Snr wann wow. N. L. mnOn of L. arn0a..n0.
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LE.
Electronic Servicing & Technology
A symptom chart lists possible symptoms and directs the technician to possible
causes below.
facts, consists of a series of soft covered, plastic-bound, 81/z" x 11"
books containing symptom/cure information on TV sets. Zenith,
Magnavox, RCA and GE are currently available in the series. Sams
reports that they will be covering
additional manufacturers on a
monthly basis. They also state that
they will issue supplemental updates to current volumes, as
necessary.
Each volume contains, according to the publisher, "time-saving
service hints" on TV sets made by
one manufacturer. For example
the RCA Quickfacts, which is in
two volumes, contains information
an RCA chassis CTC68 through
CTC91 in Volume 1, and chassis
CTC 92 through CTC 108 in
Volume 2.
A technician using Quickfacts
turns to the contents page to
locate the model or chassis number
of the television being serviced (a
model-to -chassis cross reference is
included). Once the technician has
turned to the page indicated by the
Septerr ber 1982
table of contents, he will find a list
of symptom categories to choose
from. These may include AFT/
tuner, AGC, color, horizontal/HV,
picture/sound, power supply,
raster, remote, sync, vertical or
miscellaneous.
As a specific example, if you
were troubleshooting an RCA set
with chassis CTC92, you would use
Volume 2 of the RCA Quickfacts.
The contents pages would direct
you to page 9, and if your problem
was with the raster, you would
then be directed to page 42. At the
top of page 42 and succeeding
pages are symptom descriptions
such as "No raster or sound," "Picture is red," etc. One or more
numbers associated with each
symptom description direct you to
the module/component that should
be checked.
Photos, drawings, circuit board
patterns and other aids are included to help direct the servicing
technician to the area that needs
to be checked.
When you need a
semiconductor that fits
and works,turn to
the Master:
search high and low for some replacement parts.
Or you can turn to the Master-the Sylvania ECG®
Semiconductor Master Replacement Guide.
It's called the Master because it's far and away
the industry's most comprehensive source for getting the parts you need, when you need them.
Including most hard-to -find foreign parts. And
ECG universal replacement part specifications
generally exceed the original JEDEC or application specs.
Not surprisYou can
ingly, the Master
FCG212tt
SuMV..1Pp Paca 1296
Sylvania
comes from the
people who first
mastered the universal replacement
principle-a system \
that allows a minimum
number of premium
\t
quality replacement
devices to replace almost
every original equipment
semiconductor on the
market.
With the Master
Semiconductors
,
,
working for you,
there is no need
to turn elsewhere
for replacement
semiconductors.
For your
nearest ECG
distributor, call
1-800-225-8326.
r
Replacement Guide
ertanment
Industrial
yuiprrent Maintenance and Commerci ,
Repair
If it's ECG, it fits. And it works.
PhilipsECG
A North American Philips Company
September 1982
Electronic Servicing & Technology
15
Digital building blocks:
The Schmitt trigger
A
By Bernard Daien
B
One way of considering digital
integrated circuits is that they are
functions, and should be treated as
such. The system designer simply
buys the ready-made function he
needs, plugs it in, and discards it
when it fails to perform its function properly.
Using this philosophy (employed
by many IC troubleshooters), we
can practically eliminate the need
which should be matched in impedance to both the generator and
the load in order to prevent standing waves and other undesirable
effects. Unfortunately, the bus
lines, connectors and loads used in
digital systems are usually far
+ 5.0V
for Boolean Algebra, Veith
Charts, Karnaugh Maps, etc., and,
with the aid of a simple truth table,
put our analog skills to work in
digital systems. But, in order to
accomplish this, we need to know
what the various digital building
blocks do. Obviously these ICs
were developed and marketed
because there was a need for them.
We will examine them, one at a
time, starting with the Schmitt
trigger in this article.
The Schmitt trigger is versatile
enough to be employed in both
computers and control systems,
and in many odd places, too. It has
been traditionally dismissed with a
few sentences in most digital
texts, but you will see it in many
schematic diagrams, generally
with little explanation as to why it
is there.
The Schmitt trigger can be used
as a switching contact debouncer,
for signal conditioning, as a level
detector, and in control systems,
to prevent hunting. It is also used to
convert triangular and other odd shaped waves into square waves.
-+2.4V
Uncert.in region
-+
}
Zero V
Min
0.4V
Figure
1. An ideal digital pulse for driving TTL logic circuitry. (The rise and fall
times should be less than 150ns in order
to maintain noise immunity.) The signal
may not exceed + 5.0V, nor go below
zero.
Uv\i-
"ro"
Figure 2. "Ringing" degrades the idealized digital pulse. This is due to stray inductance and capacitance forming a
resonant circuit, or to reflections on a
misterminated bus (transmission line).
"Level -triggered" digital circuits will be
subject to an uncertain "0" input level.
The maximum level also exceeds + 5.0V
and the minimum level goes below zero
volts, which is not permissible with TTL
digital circuits.
Not -so-ideal digital pulses
It is usually assumed that digital
signals have nice clean "highs" and
"lows" (ones and zeros). Unfortunately, this is not always the
case. The high frequency digital
pulses, often at frequencies exceeding several megahertz, are
really radio frequencies. They are
not sine waves, which means they
are loaded with harmonics, extending even higher in frequency.
Such signals must be piped
around on transmission lines,
16
Electronic Servicing
&
Technology
Figure 3. Long rise and fall times
degrade this digital pulse, and may
cause problems with edge-triggered TTL
circuits. The time spent in the uncertain
region is increased, with resulting noise
problems and the possibility of circuits
oscillating while in the linear mode.
September 1982
Figure 4. The symbology for Schmitt trigger digital ICs shows a Schmitt trigger
inverter (A) and a 3 -input NAND gate
Schmitt trigger (B).
from ideal transmission lines. As a
result, the clean rise and fall times
of the digital pulses become slow
rising and falling ramps, and there
is often ringing.
Some digital circuits are edge
triggered on the rising edge of the
pulse, and some are edge triggered
on the falling edge of the pulse.
Other circuits are level triggered
on a one, and some are level triggered on a zero. Degraded digital
pulses cannot trigger these
various circuits properly.
Figure 1 shows the idealized
digital pulse for triggering the
transistor -transistor logic (TTL)
family of digital integrated circuits. This is the largest, most
useful and most inexpensive family
of logic integrated circuits, and it
operates from a standardized 5V
single power source. Notice that
the high state is clearly indicated
and the low state is also defined.
There is a region between the high
and low states that is a "forbidden
zone" so far as input and output
signals are concerned. This
prevents the digital circuits from
being in an uncertain state.
Now what if ringing is introduced in the idealized pulse?
Figure 2 indicates that the signal
is alternating in and out of the
uncertain zone, with unpredictable
results in triggering level triggered circuits.
Figure 3, with sloping rise-and fall ramps introduced by the effects of capacitance and resistance
(RC time constants), and with
cumulative delays caused by passing through several circuits, will
similarly cause unpredictable
results in triggering edge triggered circuits.
Many of the problems in digital
systems arise, not from the
presence or absence of such pulses,
but rather from distortions or
delays in the pulses. In clocking,
for example, the clock pulse must
arrive at precisely the right time in
order to synchronize the system.
Of course, the clock pulse must be
effective in triggering the circuitry
involved.
Effects of non -ideal pulses
When a level -triggered circuit is
held in the high state or the low
state, it is either in saturation, in
cutoff, or in a predictable and
stable condition, functioning as a
switch. But when the circuit is held
in the uncertain region, it is
neither fully on nor fully off, but in
the linear region. As such, it functions as an amplifier with high
gain, and the output therefore may
be quite noisy. The circuit may actually oscillate at some parasitic
frequency. Switches do not have
these undesirable problems but
linear amplifiers do, and digital integrated circuits were never designed to function as linear
amplifiers.
The edge -triggered circuits have
their own problems. When the rise
and fall times are too long, the exact moment that the trigger point
Upper trigger
level
Lower trigger
level
5.0
Hys-
f
4.0
teresis
ó
3.0
â
o
I
Lets you
select from 12
Safety Listed DMMs
2.0
Only Simpson offers a full line of DMMs that are listed under UL -1244
Electrical and Electronic Measuring and Testing
Standard for Safety
Equipment.
1.0
SIMPSON DIGITAL MULTIMETER SELECTION CHART
0
I
I
E
2.0
1.0
3.0
Model
Input volts
Features
Figure 5A. The Schmitt trigger upper and
lower trigger levels for the 7414 TTL IC
(note hysteresis).
Upper trigger
level
-
Lower trigger
level
Input
Output
(Continued on page 22.)
461-2R
461-2
487/46781
463
Deluxe unit with
true RMS, pulse
detection, differential peak
Basic
low cost
cordless
462
Low cost True RMS Auto and
basic unit responding manual
ranging
unit
hold, visual/
audible continuity indication.
#Black case
464-2A/21)' 465-2A/21)
Low cost
bench
DMM with
10 amp
range
Auto and
manual
ranging,
10 amp
range
460-4A/41)
Deluxe unit.
Low power
ohms, aux.
analog meter,
10 amp
range
Ranges
26
26
26
26
23
28
27
32
Display
LCD Digaloge
LCD
LED
LED
LED
LED
LED
LED
0.1%
0.1%
0.1%
0.25%
0.1%
0.1%
0.1%
(3'h digit)
display
Basic
Accuracy
0.1%
Power
Source
Price
Figure 5B. The result of a slowly rising
and falling input, for a non -inverting
Schmitt trigger. The output goes high
when rising input exceeds upper trigger
level. The output goes low when the falling input goes below lower trigger level.
For an inverting Schmitt trigger, the output state is reversed.
Bench portable DMMs
All 2.7x8.4x9", weigh 3 lbs.
Hand portable DMMs
All 2x5.6x4.6", weight 1'h lbs.
t
9 V battery supplied,
200 -hour battery life
$257
$200
Rechargeable batteries and
er/charger supplied
AC adap
$194
$234
$244
AC operation standard. 'AC/battery ver sion optional (batteries not included)
$290/'$338 I $403/'$453$378/'$431
Choose the one that's best for you! Available at leading electrical/
electronics distributors worldwide.
SIMPSON ELECTRIC COMPANY
NSIRUMFNIS THAT
A Katy Industries Subsidiary
853 Dundee Avenue, Elgin, IL 60120
Cable SIMELCO
Telex 72-2416
(312) 697-2260
SI,.
ACCURATE
i
IN CANADA: Bach -Simpson Ltd., London, Ontario
IN ENGLAND: Bach -Simpson (U.K.) Ltd., Wadebridge, Cornwall
Circle
(9) on Reply
September 1982
Card
Electronic Servicing & Technology
17
Replace Your
Conventional Scope
With The Sencore SC6I.
The First Scope With
Pushbutton, Automatic
Readout
$3275
DIGITAL
READOUT
GSA N GSOOS27505
®
VOLTSIDIVISION
VERTIC AL
AL
POSITION
DC
O
INPUT COUPLING
DC
50
S
200
rREO
e
4
rLR
AC
2
VPP
RIA000IECT
w.
oll SECT
CHANNEL
B
INPUT
INPUT COUPLING
AC
DC
200
ÓRER[+I
.OS
.RRqF
REAOORIECT
WIT.+O[
cUM
A PPV
PROSE
D DELTA MEASUREMENTS
A
BEGIN
INTENSIFIED
A
PORTION
END
TRIGGER
C
.+
SOURCE
AC LWE
B
AUTO
NORM.
CUB
111 APPV
111
tN1EN51TY
CHAN A CHAN
B
A&B
VECTOR
FOCUS
MORIZ
POSITION
1
rS ENCORE
MODEL SC61
I
ME
o.P
E
..
TIMERASE-FRED
ATIME
®
iii
C
11
////ICE\
IT
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2
J.,e
R.
FINDER
WAVEFORM ANALYZER
P01._
O
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+GNO
v.ORI
LEVEL
_
.+BEAM
v
ART
IT®B:A
I
W.
MICROPROCESSOR CONT ROUER
{OW+I.USEATE TO 1001.2
Sencore SC6I 60 MHz Waveform Analyzer.
Cut Your ScopeTime In Half
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Cut your scope time in half?
We know that's a bold claim. But
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speed, accuracy, and ease of
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as the analog meter. Now all you
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The First Scope With Automatic
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has gone digital. No more graticuk
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can now make waveform measurements digitally accurate, digitally
fast, at the push of a button.
Make All Measurements With One
Probe Make no mistake. The SC61
is not a "piggyback" unit, but a completely integrated waveform monitoring system. You connect only one
probe and the AutotrackingTM
display digitally tracks the waveform
on the screen. You just push a
button when you want to read DC
volts, P -P volts, or frequency.
An Exclusive Breakthrough It took
four patent pending circuits to
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is a breakthrough in scope technology that virtually obsoletes
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It's 10 Times Faster The SC61 is 10
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you do is push a button instead
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speed means increased productivity.
It's 10 Times More Accurate
No matter how carefully you try
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with a conventional
scope, you will only be
5% to 15% accurate due to
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'onr..ALYZER
Just one probe and
push for DCV, PPV,
Frequency and Time.
our word for it. Try an SC61 and
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It's Easier To Use The digital readout is simplicity itself. Just push
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than the scope.
Measure Part Of A Waveform
Intensify any waveform portion with
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Guaranteed To Cut Your Scope
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SC61 will cut your scope time in half,
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Update Today Just like DVM's
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Alaska, Hawaii, Canada and South Dakota call collect at 605/339-0100
(Continued from page
How the Schmitt works
17).
occurs cannot be accurately
predicted, and in fact, some circuits may not trigger at all.
With many edge -triggered circuits in a system, the cumulative
delays may be so great that the
system becomes totally unreliable.
Of course this would be an intolerable situation, but careful examination of the pulse waveforms,
expanded on a good, high frequency oscilloscope, will reveal this
situation if a good sync source can
be found. Remember, many digital
pulses in a system are not
repetitive (incoming data, for example). In such cases you may
have to find a source of a good
sync
repetitive waveform
somewhere in the system, through
programming or in clocking, to observe the deterioration of the
waveform.
This is where the Schmitt trigger can be useful. Before the
signal is allowed to deteriorate too
far, the Schmitt can `condition' it
to be as good as new.
Ein
Figure 6A. The discrete version of a
Schmitt
trigger
(conventional
schematic).
Ein
Figure 6B. A simplified schematic of an IC
Schmitt trigger. Note: Q, and 02 are the
Schmitt trigger, while Q3, Q4 and Q5 are the
standard TTL output circuitry.
The Schmitt trigger is a form of
flip-flop, but unlike the more
familiar bistable and monostable
flip-flops, the Schmitt trigger has
two levels of triggering: an upper
level and a lower level. When the
input signal is above the upper
level, the circuit is in one state.
When the input signal falls below
the upper level, the circuit remains
in the same state, but when the
signal falls below the lower trigger
level, the circuit changes state.
Conversely, if the input rises
above the lower level, nothing happens until the signal rises above
the upper level, when a change of
state again occurs. This is called
hysteresis, and a hysteresis loop
forms the symbols for a Schmitt
trigger, as shown in Figure 4. The
various triggering levels are
shown in Figure 5.
This principle is familiar; it is
used in many common control
systems. The thermostat on the
wall that controls the heating or
cooling system is an example. If it
is set to turn on the heat at 70°F,
the heat will stay on until the thermometer reads 72°F, at which
time the system will shut down. It
will stay off until the temperature
drops below 70°F, at which time it
will again turn on and repeat the
cycle.
There is a good reason for this.
If this 2° of hysteresis were omitted, the furnace would turn on at
70°, promptly turn off again as
soon as the temperature rose
above 70°, then turn on again as
soon as the temperature dropped
to 70°, and repeat endlessly. The
furnace simply would be oscillating
on and off at some low frequency,
hovering around the 70° mark but
never stable. Of course the same
thing will happen in any digital
(switching) system because there
are only two states: on and off.
Thus your air conditioner turns on
and you complain about the cold
air on your neck, then it shuts off
and you feel warm. Thermostats
have a small adjustable hysteresis,
which prevents the rapid cycling of
such systems, reducing quick
Eout
Figure 6C. A Schmitt trigger made of TTL family inverters.
22
Electronic Servicing & Technology
September 1982
wearout of valves, switches, etc.
The Schmitt trigger has a defined hysteresis, and when electrical control signals for turn-on
and turn-off are supplied to the
Schmitt, it provides for a dead
band, similar to the two degrees in
the thermostat. Remember, the
system turned on at 72°, and off at
70°, but absolutely nothing happened within those two degrees.
Circuitry
The conventional schematic for a
Schmitt trigger made of discrete
parts is shown in Figure 6A, the
internal circuit of an integrated
Schmitt trigger in 6B, and a
Schmitt trigger made of two logic
gates in 6C, but they all operate
similarly.
An input resistor should be used
in series with the Schmitt input. In
some cases, this resistor partially
determines the operating points of
the circuit. It is preferable to drive
the Schmitt from a low impedance
source, such as a logic IC, so that
the driving source resistance does
not affect the operating points.
Some Schmitt ICs have an internal
input resistor.
The Schmitt trigger can also be
implemented with a single operational amplifier and a few
resistors, but that circuit rightly
falls under op -amp applications,
which is a non-digital subject.
All of these circuits simply use
do positive feedback. In the discrete version, we use two transistors in an emitter-coupled,
bistable flip-flop, modified so that
the trigger level changes, depending upon which side of the flip-flop
is cut off. The IC version uses
essentially the same circuit, with a
totem -pole digital output. The
Schmitt, made of two TTL inverters in series, functions like a
single, non -inverting, gain stage
(which is the reason the op -amp
can be used).
The integrated CMOS Schmitt
triggers use more complex and
varied circuitry internally. Different manufacturers use different
circuits. This is partially due to the
fact that CMOS is "Complementary MOS", with P -channel and
N -channel devices in series across
the power supply. At any rate, the
CMOS Schmitts in integrated
form do not resemble the previously described circuits, although they
perform the same function.
THE PERFORMANCE/
PRICE STANDARD
-PURPOSE
TEK 2200 OSCILLOSCOPES
MULTI
Tek's most successful
scope series ever: At $1100-$1400,
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Scale factcrs frcm
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to
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Two high -sensitivity
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MHz bandwidth
from 10 V/div to 20
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Delayed sweep
Sweep speeds:
from 0.5sto50ns. measurements:
To 5 ns/div with X10 Accurate to < 3%
with single time magnification.
base 2213; to
-1.5%with dual
time -base 2215.
MHz.
L
Tektronix
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You can order, or obtain more
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Ask for Department 11237
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Call (206) 253-5353 collect.
In
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ektronix
COMMIT TED TU EXCELLENCE
Copyright
© 1982
Tektronix. Inc. All rights reserved 136-1
September 1982
Electronic Servicing & Technology
23
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To earn these awards just purchase RCA receiving tubes in
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Remember, CMOS does not operate
from a fixed 5V supply, but can
work from 3V up to about 20V.
The trigger levels will shift accordingly, so be careful to check the
power source if the CMOS Schmitt
does not trigger at the expected
points.
Both the discrete and the logic
gate circuits have adjustable triggering, depending on the resistor
values, while the TTL Schmitt IC
has fixed levels. This is because the
internal resistors cannot be
changed and the supply voltage is
fixed at 5V. (The CMOS Schmitt
trigger levels vary with the applied
supply voltage in discrete, gate
and IC versions).
The output of the Schmitt consists of fast -rising and fast -falling
waveforms, which are well suited
to driving edge-triggered circuits
in digital systems. Thus the
Schmitt provides near -ideal digital
pulses for both level -triggered and
edge -triggered circuitry. Because
digital systems are intended for
use with properly shaped pulses,
the coupling capacitors are large
enough to pass such waveforms. If
the digital signal is allowed to
24
Electronic Servicing & Technology
deteriorate sufficiently, pulses will
have rise and fall times too long to
pass through the coupling
capacitors. Stated another way,
the capacitors may be too small to
accommodate
the
pulse
waveshape.) The Schmitt restores
the waveshape before it is degradInverter
Switch closing
H>Eout
Output
waveform
Figure 7A. Switch contact bounce
eliminators; normally open switch contact circuitry.
Inverter
aut
Switch opening
Figure 7B. Normally closed switch contact circuitry. Note: The inverter is used
in these circuits because the Schmitt
trigger shown is an inverter (which is
common). The output would therefore be
an inversion of the input if the second inverter was omitted.
September 1982
ed to the point where problems
arise.
Integrated circuits
Schmitt triggers are readily
available in IC form. In transistortransistor logic (TTL) the 7413,
7414 and 74132 are common. The
7413 is a dual, 4 -input, NAND gate Schmitt. The 7414 is a hex
package, with single -input Schmitt
inverters. The 74132 is a quadruple, 2 -input, NAND Schmitt.
In CMOS, the 4093 is a quadruple, 2 -input, NAND Schmitt. The
4584 is a hex package, with six
Schmitt inverters.
It should be noted that there are
Schmitt triggers available with tri state outputs, for those into computer circuitry. It is a simple matter to deactivate the tri -state
feature, however, in which case
the trigger operates like a conventional dual -state -logic IC.
Contact debouncing
Digital systems use many
mechanical switches and relays.
The keyboards on some machines
have many such contacts, and
there are switches in the power
with your purchase of RCA Receiving Tubes
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Value: $43.00
supply lines and other locations.
These switches tend to bounce for
milliseconds before settling down,
particularly if they are snap -action
switches, such as toggle switches.
Of course these multiple openings and closings wreak havoc in a
digital system. The Schmitt offers
a quick, simple and inexpensive
solution. Figure 7 shows circuits
for debouncers on normally open
and normally closed momentary
contact switches, such as might be
encountered on keyboards. The
RC networks provide smooth rise
and fall times of the switch output,
but the Schmitt converts these to
nice square wave pulses without
any bounce.
As indicated in the caption of
Figure 7, Schmitt triggers are
often inverting circuits and many
therefore require another inverter
to prevent voltage waveform inversion.
A
X
B
Receiving
Tubes
RCA Distributor and Special Products Division, Deptford, NJ 08096
Truth tables are simply tables
listing the output states for every
combination of inputs. Thus, if we
have a 2-input gate, there are four
input combinations (1-1, 0-0, 1-0
Output
Inputs
and 0-1) with an output for each of
X
B
these combinations. This is simple,
but what if you have a circuit with
many inputs, two outputs and
o
o
o
clocking? The truth table makes
things quite clear, in an easy-touse format. In this series, the truth
table will be stressed as an esseno
tial working tool.
Figure 8 shows the truth table
for
a commonly used TTL digital
o
circuit, along with explanatory
notes, which make the use of the
table obvious. A Digital Circuits
o
Data Book, either TTL or CMOS
from one of the major semiconductor manufacturers is
Figure 8B. An exclusive 2 -input OR gate
recommended. (They all have them
truth table. Note: The table shows that' for free or a small charge.) Study
the output goes high when either input
the truth tables for the simpler cirgoes high. The output is low when
neither input is high or when both inputs cuits at first, then the more complex ones, until you can underare high. No inversion takes place. This
differs from a simple 2 -input OR gate,
stand them without difficulty.
which has a high output when both inare the starting point for a
They
puts are high.
digital education.
Exclusive 2 -Input OR Gate
Truth Table
1
i
1
1
Symbol
Figure 8A. An exclusive 2 -input OR gate.
September 1982
Electronic Servicing & Technology
25
Servicing
conduction -time
regulation
By
-lomer
L.
Davidson
The powersupply module S in J.C. Penney models 2868 and
288E is mcunted on the chassis side near the horizontal -sweep
section. This position allows many voltage, waveform and
resistance tests without removing the module. A technician's
finger points to filter capacitor C853.
When a technician analyzes a defect in an unconventional electronic system, his knowledge
about its purpose and the circuitoperation theory can be valuable.
This is the case with B + regulation in the J. C. Penney "S"
module. Penney models 2868 and
2888 (Photofact 1370-1) and
several Panasonic color -TV receivers use the S module.
Regulator purpose and theory
Regulation of the B+ applied to
the horizontal -output transistor
also regulates horizontal sweep
and high voltage. If the regulated
supply voltage becomes too high,
the horizontal transistor and other
components can be damaged.
When the regulator output is too
low, the picture is small or missing. Therefore, correct operation
of the regulator is vital.
Figure 1 has simplified schematics that illustrate the basic
principle behind S module regulation. The Figure lA schematic
shows how an adjustable dc
voltage can be produced by varying the on -time duty cycle of relay
contacts that control application of
dc voltage to an integrating
capacitor (C853 in the S module).
For example, if the relay contacts
are closed for 10% of the total
time, the output voltage will be
about 10% of the supply voltage.
26
Electronic Servicing & Technology
However, several conditions input voltage that is fed to one of
must be fulfilled. A current - the triggering transistors.
limiting resistance or inductance is
Remember that the SCR is trigrequired between the supply gered by a gate -to -cathode positive
voltage and the switching contacts pulse. After triggering, it remains
or other switching device. Without conductive until the anode voltage
the current -limiting inductance (a (parabolic-waveshape dc voltage)
resistor would produce excessive falls below the desired + 122V at
voltage drop here), the circuit the SCR cathode and C853.
would be peak -reading, and the
Regulation of the + 122V is prostorage capacitor would charge to duced by varying the turn-on point
the full supply voltage, preventing of SCR TR805 on each SCR-anode
any significant voltage variation parabolic cycle. As shown in the
when the duty cycle is varied.
Figure 1C drawings, a light load
Also, the repetition rate vs. the on the regulator output (or a
storage -capacitor capacitance higher input voltage to L801) trigmust be within certain limits. gers the SCR on later in the cycle,
Faster repetition rates allow the reducing each conduction time.
use of a smaller capacitance, while
At the other extreme, a heavier
a slower repetition rate demands a load on the regulator output (or a
larger capacitance for acceptable reduced voltage at the input of
operation.
L801, perhaps from low line
The previous circuit has no pro- voltage) causes the circuit to trigvision for automatic regulation of ger the SCR earlier in each cycle.
voltage. Additional circuit ele- Of course, longer conduction times
ments needed for regulation are supply more total current and
shown in Figure 1B. Unregulated higher voltage during each cycle.
and unfiltered 120Hz parabolic dc Figure 2 shows the entire reguvoltage pulses from the bridge rec- lator schematic (from Photofact
tifiers are the input power source 1370-1). Transistor TR801 reto the L801 current -limiter in- ceives a sample of the input paraductance. An SCR replaces the bolic waveform, and a sawtooth
previous relay, giving the waveshape is produced at the
necessary precise and fast switch- TR801 collector by C807 and
ing. Turn -on point of the SCR R808. The sawtooth is fed to the
must be synchronized to the 120Hz TR802 base, but the TR802 emitripple frequency. This synchronism ter voltage is controlled by the
is accomplished by a sample of the C853 voltage through R816 115V
September 1982
For more information, or to order
along. There's less time wasted
transferring a set back to your shop. Make your QUICKFACTSTM volumes, see your
local PHOTOFACT® Distributor, or call
more calls and profits in a day.
800-428-3696 toll free, or 317-298-5566
It's COMPREHENSIVE. QUICKFACTSTM
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are organized by manufacturer, you only
need to buy the books covering the
manufacturers you service. Why pay for
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don't need it.
It's CROSS-REFERENCED. Models
SAMS BOOKS
Howard W. Sams & Co., Inc.
contained in QUICKFACTSTM are crossbecome a computer programmer to find
4300 West 62nd Street, PO. Box 7092
referenced to PHOTOFACT® numbers
the answers to your servicing questions.
Indianapolis, IN 46206
to further aid you in servicing.
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It's ILLUSTRATED. Photos point out each
answers in less than a minute.
problem area to help make component
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QUICKFACTSM IS THE
REFERENCE PREFERENCE.
Offer good in USA only and expires 12/31/82. Prices subject to change without notice
Circle (13) on Reply Card
September 1982
Electronic Servicing & Technology
27
control and reference-amplifier
transistor TR804. Therefore, the
TR802 (PNP-type) cut-off bias is
changed to forward bias (thus
causing TR802 C/E current) at a
point on the negative -going
sawtooth (at its base) that moves
according to the TR802 emitter
voltage. Voltage variations at
C853 determine when (during each
cycle) TR802 draws C/E current.
In other words, the conduction
time varies in phase according to
the C853 voltage.
Each pulse of TR802 collector
current is moderately short. The
waveshape is sharpened by the
small -value C808 coupling
capacitor, and the effect of the
waveshape is narrowed even more
by the absence of any forward bias
at the TR803 base (except the
signal itself). The resulting narrow
negative -going pulses at the
TR803 collector are coupled and
phase -inverted by triggering
transformer T801, which delivers
a positive -going pulse to the SCR
TR805 gate sometime during each
cycle of the 120Hz ripple. As ex -
CURRENT
LIMITER
L801
DC
ADJUSTABLE
SUPPLY
DC
VOLTAGE
LOAD
RELAY
C853
INTEGRATING
STORAGE
CAPACITOR
VARIABLE
DUTY CYCLE
DC -VOLTAGE CONTROL
plained, a lower voltage at C853
forces these gate pulses (that start
the SCR conduction) to appear
earlier in each cycle, producing a
longer time of TR805 current flow
into filter capacitor C853.
SCR conduction causes the
right-angle notch on the parabolic
waveforms in Figure 1C. Until SCR
TR805 conducts, it is an open circuit, and the anode waveform follows the parabolic shape. When
TR805 conducts, it becomes the
equivalent of a near short between
anode and cathode. The anode sigFigure 1 These schematics and drawings explain how variable times of
power -supply conduction can produce
regulation. Left, variable dc voltage can
be obtained by this circuit, which varies
the duty cycle (on -time) of power applied
to storage capacitor C853. However,
there is no automatic regulation. Below
left, automatic regulation is performed
by a triggering circuit synchronized to
the 120Hz ripple frequency. SCR TR805
is forced to conduct earlier in each
120Hz cycle when more power is needed.
A power -filter circuit completes the
regulation and filtering. Below, these
drawings show idealized waveforms at
the SCR TR805 anode during light and
heavy loads on the power supply. The
anode waveform follows the ripple until
the SCR conducts, and then it is connected to the C853 voltage. This accounts for the missing sections.
(A)
+169V
ss
+
L801
122V
UNREGULATED
B+
+110V
FULL WAVE
UNFILTERED
PARABOLAS
A
TR805
SCR REGULATOR
SHORT
+122V
4 TRANSISTOR
TRIGGER
CIRCUIT
9uß
OV
CONDUCTION
TIMES
SYNC
'1'
C853
1200µF
LIGHT LOAD REDUCES
CONDUCTION TIMES
(C)
R816
+115V
AD.!
2000
PARTIALLY REGULATED
AND FILTERED
+
169V
+121V
TR851
APF OUTPUT
1
TRANSISTOR
R820
CIRCUIT
TP S1
0.8212
C811
Y
REGULATED AND
FILTERED
+115V
SUPPLY FOR
HORIZ OUTPUT
1µF
(B)
LONG
CONDUCTION
TIMES
SIMPLIFIED J.C. PENNEY REGULATOR
28
Electronic Servicing
&
Technology
September 1982
_
,
HEAVIER LOAD LENGTHENS
CONDUCTION TIMES
OV
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Circle (14) on Reply Card
September 1982
Electronic Servicing & Technology
29
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Rgure 2 The entire S module power-supply circuit is shown here from Photofact 1370-1. Follow the circuit as theory and servicing information are discussed.
Figure 3 A pen at the bottom points to
TP-S1, where the + 115V
should be. Just above it is power transistor TR806. Voltage control R816
is pointed out by the arrow.
testpoint
nal comes through inductance
L801; therefore, the maximum instantaneous current is limited.
Because the anode current is
limited, but the cathode current is
not (1200 F can store a large
potential current), the anode
assumes the cathode and C853
waveform (nearly pure dc voltage,
or a straight horizontal line on the
scope screen). This horizontal line
is retained until the input parabolic
voltage drops below the + 122V at
the SCR cathode. At that point,
SCR conduction ceases, and the
anode -voltage waveform once
again follows the parabolic shape.
Therefore, the width of this
missing section indicates the time
of C853 charging. A narrower section proves the regulator action is
30
Electronic Servicing & Technology
operating below maximum, perhaps because the horizontal -sweep
load is low. A heavier load on the
+ 115V supply forces a normally
operating regulator to increase the
time duration of SCR conduction,
thereby widening the notch in the
anode waveform.
Incidentally, the actual SCR anode waveform is not a true
parabola because L801 integrates
the bridge -output parabolic wave shapes to more nearly resemble
sinewaves. Of course, this slight
discrepancy has no effect on the
circuit operation.
To summarize: Regulation of the
B + 115V supply in the Penney/
Panasonic S module is accomplished by triggering-on an SCR
for varying lengths of time according to the current demands. Therefore, a shorted SCR or a permanent conduction through the SCR
will increase the + 115V supply to
a level that probably will ruin some
horizontal -sweep or high -voltage
components. If the SCR is not triggered on at any time, the + 115V
supply will have no voltage (there
is no parallel path). Of course, erratic triggering can produce a
varying or low voltage from the
+ 115V supply. These condensed
symptoms will help technicians
know what voltages and components to check when the
regulator malfunctions.
Some ripple and line -voltage
bounce is present at C853. Therefore, an automatic power filter
(APF) consisting of transistor
TR806 and power transistor
September 1982
TR851 was added (Figure 1B). The
failure of TR851 to pass sufficient
current also can eliminate or
reduce the + 115V supply. If
TR851 is shorted between collector and emitter or is biased into
saturation, the + 115V output will
be slightly high.
Isolate the problem
Several tests should be made before the S module is replaced or removed for repair. Excessive horizontal -output transistor current
might be loading down the + 115V
source. Also APF transistor
TR851 might be defective in a way
that would destroy some components of a replacement module.
TR551 horizontal -output transistor and TR851 APF transistor are
located on the chassis heat sink
behind the S module. Both transistors should be removed and
tested externally before any other
tests are made. Check particularly
for leakages after the usual evaluations are made.
After it is certain the APF transistor (TR851) is in perfect condition, reinstall it (or a new replacement), but do not reinstall the horizontal-output transistor until the
+ 115V -supply voltage has been
measured at testpoint TP -S1
(Figure 3). Zero or low voltage
there indicates a defect in the S
module.
A visual inspection of the module
should be made to find any burned
resistors or other apparent defects. Voltage and waveform tests
can be made easily because the
system, so when you decice to replace or design with
RCA, Philips -ECG and G.E., to name a few. And
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Only three years ago TCG started out with just ten
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ment equivalents right on the package. So finding the
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guys are getting more than a
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We've grown so rapidly because we give you more
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No matter what area of electronics you're into, TCG
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r
Circle (38) on Reply Card
September 1982
Electronic Servicing & Technology
31
filtering without removing the
supply voltage. Sometimes the
transistor will test good (even out of -circuit) but apparently break
down under load. Replace it when
there is any doubt.
Some modules have been modified by addition of D14 (Figure 4),
a 15V zener. When D14 is added,
diode D810 and varistor D811 are
removed. Check D814 and D812
when the raster shows hum bars.
TR851
D811
APF
(§)/
REMOVED
MODIFICATIONS
TR806
APF AMP
R818
D814
,,rADDED
2
3300e
R819
569.
C810 L--ri
D813
100µ F
R825
180K
Figure 4 Some Penney Panasonic modules have modifications that remove diode D810
and varistor 0811 while adding protective zener diode 0814.
module is accessible at the end of
the chassis. Applications of heat
and coolant have been effective in
locating thermally intermittent
components on these modules.
Zero or low voltage
When voltage measurements at
TP -S1 show low B+ voltage, first
measure the dc voltages at anode
and cathode of SCR TR,805. If low
or no voltage is found at the anode,
the problem is almost certain to be
in the bridge rectifier or ac -input
circuits. Of course, the module input connections and L801 should
be tested for continuity. Also, test
all diodes of the bridge rectifier.
Scope the TR801 collector for
the sawtooth waveform. A proper
waveform clears the TR801 stage
of suspicion. A reduced-amplitude
or incorrect waveform at the collector might indicate a bad TR801
transistor or it might be caused by
a defective component in the base
circuit. Overloading of the + 115V
supply also might interfere with
the sawtooth waveform.
Of course, an improper sawtooth
waveform at the TR801 collector
will prevent all following voltages
and waveforms from being nor32
Electronic Servicing
&
Technology
mal. In -circuit transistor tests
should be made; They are often
sufficient to locate a defective
transistor.
Overloads sometimes overheat
R819 and R818, so they should be
tested and replaced if out of
tolerance.
Symptoms of a defective C853
filter capacitor vary greatly,
depending on the exact defect. Ex-
cessive leakage reduces the
+ 115V supply voltage and increases the ripple. A shorted filter
should trip the circuit breaker. Insufficient capacitance also reduces
the + 115V supply voltage. Some
versions of the circuit had an
800µF filter instead of 1200µF.
When paralleling the old filter
with a new one, connect it when
the power is turned off, turn on
the power and notice any change
or improvement, and then turn off
the power before disconnecting
the test capacitor. Use a capacitor
of at least 800µF during the test.
Hum bars
The most likely cause of hum
bars in the picture is a bad TR806
APF transistor. Internal C/E
leakage reduces the electronic
September 1982
Narrow raster
A narrow picture can be caused
by either insufficient regulated
voltage or problems in the horizontal -sweep circuits. Therefore,
the + 115V supply voltage should
be tested first.
In one case of narrow picture,
the regulated -output voltage was
very low. When the R816 + 115V
adjustment control was rotated, a
maximum of only + 98V was obtained at the cathode of SCR
TR805, and even lower voltage at
TP -S1.
All do voltages in the entire
regulator circuit measured low.
But there was a more important
clue: Resistor R819 (56f1) was excessively hot and this indicates a
problem with filter capacitor C853.
Paralleling C853 with another
another 1200µF capacitor eliminated the narrow picture.
A Christmas Tree or other
unstable flashing raster is another
symptom of an open or partially
open C853.
Intermittent raster
Another Penney 2888 television
developed an intermittent raster.
When the raster disappeared, the
+ 115V became zero. At the same
time, the emitter and base of
TR801 checked the same + 43V,
with a collector voltage of + 19V.
Also, TR802 had about the same
voltage at all three leads. TR801
and TR802 were replaced, but the
voltages still were wrong, and the
intermittent continued.
When canned coolant was
sprayed on C805 (Figure 5), the
raster and the + 115V supply returned. C805 was warmed slightly,
and the raster disappeared. No
doubt remained; C805 was intermittent. A new capacitor cured the
problem.
Since that time, several other
2888 chassis were cured of inter-
mittent operation by replacement
of C805. When C805 opens, no
GENERAL ELECTRIC AND YOUR
LOCAL ELECTRONIC PARTS
DISTRIBUTOR MAKE FINDING
THE RIGHT PART EASY.
su9Sested
NDUäTORS FOR
SEMICONDUCTORS
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authorized distributors it your state, your source
for tie GE Guide as well as the parts you need.
To
GENERAI eEIECTRIC
Circle (15) on Reply Card
September 1982
Electronic Servicing & Technology
33
UNFILTERED
CRITICAL CAPACITORS
B+
TR802
TR801
C805
CLIPPER
SAWTOOTH,:aEN
lµE
R803
r
8200
L-
C807
1µF
Figure 5 Capacitors C805 and C807 are
responsible for most cases of flashing raster
and intermittent raster.
120Hz parabolic waveform can
reach the TR801 base, no sawtooth
can be formed by C807 at the
TR801 collector and no TR803
pulse can be produced, so SCR
TR805 is not triggered into conduction and no voltage can reach
filter C853.
One warning: Replace C805 only
with the specified 1µF value; a
larger capacitance (perhaps 5µF or
10 µF) can cause motorboating or
self-oscillation.
A flashing raster
Regulator -circuit capacitors
usually are responsible for flashing
rasters in these models. Check
C805 (already mentioned), C807 at
the TR801 collector circuit (arrows
in Figure 6 point to these capacitors) and C810 in the TR806 circuit. In fact, it is wise to replace all
three and thus save valuable testing time.
Electrolytic capacitors tend to
lose capacitance by drying out.
Testing with a digital -capacitance
or an ESR meter is strongly
recommended.
Poor regulation
Visual proof of poor + 115V supply regulation is a noticeable
change of raster size between low
and high brightness scenes.
These are some components that
have caused poor regulation in the
past:
34
Electronic Servicing
&
Technology
Figure 6 The arrow at top points to C807,
and the lower arrow shows the location
of C805 on the J C Penney S powersupply module.
zener diode D809 (15V rating) in
the TR804 emitter return,
TR803 pulse -amplifier transistor,
TR804 reference -amplifier transistor,
bias diode D806 (base circuit of
TR803) and
resistor R817 (which is between
R816 adjustment control and
ground).
In addition, corroded and erratic
contacts inside R816 adjustment
control can produce mysterious
voltage variations. R817 is 18000
and R816 is 5000 in some S
modules, while LR817 is 47000
and R816 is 20000 in others. Of
course, these ratios must be maintained during replacements.
Alternate warming and cooling
of suspected capacitors often will
force the symptom to appear or
disappear. This is sufficient proof
for replacement.
September 1982
Replace any resistors that appear burned or discolored. R817
and R815 are the ones most often
ruined.
Critical components
Repairs made on the Penny S
module over the years have shown
several components that often
become defective. Therefore,
many modules can be repaired by
routinely replacing those few components.
Transistors TR851 APF output
and TR806 APF amplifier often
become leaky and therefore should
be checked for resistance. TR851
should be removed from its socket
for these tests. But if R818 and
R819 show signs of discoloring or
overheating, TR851 should be
replaced without further tests.
When TR851 is shorted, often
TR806 also is shorted.
SCR TR805 usually can be
tested sufficiently by removing it
from its socket and measuring the
various resistances. Typically a
500 reading is obtained between
gate and anode. Readings below
400 can indicate a problem. Between cathode and anode, a typical
TR805 tests 100 MO or higher.
Resistance of less than 50 MO calls
for replacement.
Critical capacitors and burned
resistors have been mentioned
previously. Other less critical components usually can be tested with
sufficient accuracy in circuit.
Conclusion
For symptoms of no raster and
no high voltage, first measure the
voltage at testpoint TP-S1 (Figure
3). If the reading is + 115V or
slightly higher, the regulated supply is normal and the problem is in
the horizontal -sweep circuit.
When the TP-S1 voltage is very
low or zero, measure the dc
voltage (and scope the waveform)
at SCR TR805 anode (case). Nor-
mal dc voltage and waveshape at
the anode indicates the defect is in
the + 115V regulator, and further
tests should be made there.
When all repairs are thought to
be finished, the R816 adjustment
control should be rotated to produce + 115V at TP-S1. If this cannot be done, the repair is not completed. The final step should be ob-
taining the correct
+ 115V
regulated voltage at TP -S1.
TROUBLESHOOTING
TIPS
No picture and no sound
RCA CTC 108A
(Photofact 1937-3)
A
ly was responsible. Ohmmeter
tests around the + 26.1V supply at
Circuitrace 6 quickly located an
These symptoms proved the
horizontal -sweep operation was
normal. The most likely cause of
these non -connected failures was
trouble in one or more power
sources.
Power -supply voltages at Circuitraces 9, 8, 7 and 6 were zero.
Of course, the Circuitrace 9, 8 and
7 voltages come from the
Circuitrace-6 source, so the lack of
+ 26.1V at Circuitrace 6 apparent-
open CR111 diode rectifier.
Replacement of CR111 restored a
normal picture with good sound
and allowed operation at any
reasonable line voltage without
shut -down.
J. T.
Fort Washington, MD
preliminary inspection
-ÿ
u-
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After the fuse, transistor and
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NEW JERSEY: 201-688-0300
Circle (16) on Reply Card
Sl(MCURE
Symptoms and cures compiled from field reports
of recurring troubles
r
A
Chassis- RCA CTC101
1
ü
PHOTOFACT -1945-2
Chassis-
RCA CTC101 (or CTC99)
2
PHOTOFACT-1945-2(1895.1)
Q501 PNP
Q502 NPN
Q505 NPN
ERROR AMP
PRE DRIVER
TOP DR'VER
U400
VERT-HORIZ
COUNTDOWN
12.
C436
R448
CR428
)»
IIt
.0039
R455
R446
C431
220K
I015
LEAKAGES
OPEN
Symptom-Vertical linearity
is poor with slight foldover
Symptom-Horizontal locking
at center and faint retrace lines at top
Cure-Check for leaky junction in transistors 0501,
Q502, Q505 and 0506, and replace any defective ones
erratic
is
critical, and start-up is
Cure-Check capacitor C436 and replace it if out of
tolerance
-r
Chassis-
RCA CTC108
3
PHOTOFACT -1937-3
Chassis-RCA CTC109
4
PHOTOFACT- 1952-1
OVERCURRENT
C436
R449
j470K
C706
SHUTDOWN
R450
750K
INCREASED
R451
22µF
INCREASED
150K
,/
Symptom-Erratic shut-down at high brightness
Cure-Check resistor R727 and replace it if out of
Symptom-Marginal HV regulation, slight blooming at
high brightness
Cure-Check resistor R449 and replace it if out of
tolerance (increased)
tolerance (increased)
Chassis-
RCA CTC109
5
PHOTOFACT -1952-1
Chassis- RCA
CTC109
6
PHOTOFACT-'952-1
INTERMITTENT
Q411
T401
HORIZ
+26V
DRIVER
R325
R324
TO
Q412 HORIZ
100e
1600
OUTPUT
Q302
REGULATOR
C332
001
+12V
CR302
SJPPLY
ZENER
C327 +
220µF
LEAKY
Symptom
- Bands of noise at top and ba:tom of picture
Cure-Check and/or replace horizontal -driver transistor
r
Symptom-No color or intermittent color
Cure-Check regulator transistor Q302 and replace
it if
erratic
Q411
J
36
Electronic Servicing & Technology
September 1982
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When you price
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Easy to Install
Reasonably Priced
UPS Shippable
Weight 125 Pounds
More than 100
Channels Accessible
THE STAR VIEW 12K SYSTEM KIT CONTAINS:
12 Foot Antenna
Azimuth Elevation Mount
24 Channel Receiver
120 ° Low Noise Amplifier
Feed Horn
Cables & Connectors
No Modular Included
(May be ordered separately for $79.95)
Available through your local Craig Star View dealer Call or write for information
Dealership inquiries welcome Price subject to change without notice.
H&R COMMUNICATIONS, INC.
Route 3, Box 103G
Pocahontas, Arkansas 72455
Subsidiary of Craig Corp.
Call 800-643-0102
or 501-647-2291
Circle (18) on Reply Card
September 1982
Electronic Servicing & Technology
45
A reading
on the DMM market
Not too many years ago, elec-
tronic multimeters were
generally quiet, mundane instruments. You would plug the
probes into the appropriate
plugs for the function to be
measured, set the function and
range switches, touch the
probes to the test points and
watch the needle move.
As you know, things have
been changing. LCD digits
have, to a great extent, replaced meter movements, autoranging in many meters has
eliminated the problem of exceeding the selected range,
audible beeps give continuity indications, alarms tell you when
you're overrange and auto polarity makes it unnecessary
to switch probes when you come
across a negative value. One
meter even contains a voice synthesizer and will give you a verbal reading: great when you're
taking readings on an IC and
one slip to look at a reading can
mean disaster.
As electronics technology has
moved ahead by leaps and
bounds, it has changed not only
the instruments we use to
measure, but also the circuitry
to be measured. With more con-
Extech
International
sumer electronic products
featuring digital circuitry, for
example, it becomes necessary
to provide the means with which
to measure the parameters of
these circuits. Meter manufacturers have responded with
newer meters capable of
measuring these quantities:
logic probes, signature
analyzers and more.
The following pages contain a
sampling of the
multimeters available
Some features these
ments offer over their
cessors are smaller size,
many
today.
instrupredelighter
weight, more capabilities in a
single package, greater ruggedness and higher accuracy.
46
Electronic Servicing & Technology
A
new hand-held,
LCD -
display, precision digital
multimeter has been introduced
by Extech International.
The multimeter features 0.1%
dc voltage accuracy; full ranges
of Vdc, Vac and mA, Ohm;
200µA range for lower power
circuits; overload protection on
all ranges; and transient protection to 6kV. In-line, color -coded
push -buttons are easy to use,
September 1932
and the function panel allows
fast range selection.
Other features include a 3'/2 digit LCD display with auto
zero, auto polarity and low battery; high voltage for diode test;
low range for in -circuit measurement; recessed input jacks;
all functions and specifications traceable to NBS; and a
tilt stand.
Circle (113) on Reply Card
There is no need to zero the
945, and polarity sensing and
display are automatic. Because
Data Precision
of the patented Isopolar
reference circuitry, accuracy
and linearity are as good for
negative voltages as for
positive.
All the functions and ranges
of the unit are overload protected. Any do voltage range
will withstand ± 1000V.
The ac voltage ranges are protected to 700V rms and
± 630dc (± lkVdc above the 2V
range). Resistance ranges will
accept 250Vdc as well as Vac,
and all do and ac current ranges
are protected with a 2A, 250V
fuse. A spare fuse is shipped inside each case.
Optional accessories are
The model 945 is a full function, 41/2 -digit multimeter
packaged in a high -impact
plastic case. With a high contrast LCD display, 26 -range
capability and battery operation, it is ready to go where you
go - into tight racks or crowded
equipment bays - out to production or into the lab.
The unit gives added sensitivity on all functions and an improved accuracy spec. The
Model 945 closely matches
bench-top models in performance and offers the convenience
of 1 -hand operation.
As an example, look what the
added 200mV, full-scale range
buys you in making critical lowlevel do voltage measurements.
This same advantage of added
sensitivity is available on all
functions.
The 945 has additional circuitry that blends the patented
Ratiohmic technique with a constant current source. The result
is accuracy and stability plus
knowledge of the exact conditions under which resistance
measurement is made. The test
current is independent of the
device under test and is determined only by the range
selected. Similarly, the displayed reading is not just the
resistance of the device under
test, it is also the voltage across
the device under test. (Full scale
is always 2.0000V.) These
features allow increased versatility of measurement in the
resistance mode. For instance,
the forward V -I characteristic
of diodes can easily be measured
by selecting the resistance
range having the test current of
interest and recording the
displayed reading (voltage, ignoring the decimal point).
In -circuit measurements are
made by selecting resistance
range so that the displayed
reading is less than 2500 counts,
which allows the test voltage to
be less than 250mV and any
silicon semiconductors will not
be biased into conduction. The
results of such a measurement
are shown here for an IN 4148
available to increase the versatility of the unit. In addition
to a battery eliminator and vinyl
carrying case, optional probes
extend do voltage measurements to ± 40kV, ac voltage to
500MHz, do current to ± 100A
and ac current to 1000A.
An
temperature probe is also available for measurements from
-65°C
to
150°C
with
± 1°C basic accuracy. A thermocouple adapter (TP161 J or
K) allows you to measure temperature from - 85°C to 800°C
within 2°C accuracy.
All specifications of the 945
are warranted for one year of
operation. (The instrument
itself is guaranteed for two
years.) All units are subjected to
a burn-in cycle before calibration, and final test certification
is supplied with each unit that is
shipped, as well as a Certificate
of Conformance showing NBS
traceability.
Should your 945 ever need
servicing, a complete operating
and service manual is provided.
Only standard commercial components are used in the 945, and
accessibility is excellent. Four
non -interactive adjustments accomplish a complete recalibration in less than five minutes.
silicon diode.
September 1982
Circle (111) on Reply Card
Electronic Servicing & Technology
47
Heath
Company
Heath Company has added
two new models to its line of
portable digital multimeters,
the IM -2262 and the IM -2264.
Designed for the laboratory,
service technician or hobbyist,
both the IM -2262 and IM -2264
feature low -profile cabinets,
multiple measurement ranges
and excellent performance, according to a company spokesman. True RMS capability provides accurate ac readings from
both sine -wave and non -sine wave inputs.
Measuring 3"x8.5"x11" with
handle folded, both feature a
special color -coded front panel
with push-button switches for
additional convenience and easy
of use.
The IM -2262 measures voltage from 200mV (full scale) up
to 1000Vdc and 750Vac, do and
ac current from 200µA (full
scale) up to 10A, resistance
from 2000 to 20 MO (full scale).
The resistance function includes
a low (0.2V) test voltage, up to
2000kO range, to allow in circuit measurement of circuits
using semiconductors. A diode
test function allows checking
the forward and reverse conduction of semiconductor junctions. An MOS/LSI (metal-oxide
semiconductor/large scale -
integration) IC has the dual slope, analog -to-digital conversion circuitry.
When calibrated to laboratory
standards, the IM-2262's full
scale accuracy is 0.25% do and
0.5% ac (with frequency
response specified up to 20kHz).
Built-in references, which allow
fast, easy calibration in the
field, provide full-scale accuracies of 0.5% do and 1% ac (with
frequency response to 10kHz).
The
IM -2264
deluxe
multimeter features extended
measurement capabilities and
additional convenience features. It measures voltage from
200mV to 1000Vdc/750Vac,
current from 200µA to 10A,
resistance from 2000 to 20MO
and semiconductor conduction
(both forward and reverse).
In addition, a flashing crestwarn LED alerts the operator
when the crest factor of ac inputs is excessive, which could
lead to possible measurement
error for non -sine wave inputs.
A switch -enabled alarm function allows quick testing of
voltage and continuity, without
having to view the display, and
an auxiliary, auto -polarity
analog meter reflects 0 to full-
scale measurements to supplement the digital display, making
nulls, peaks and measurement
trends easier to follow.
All of the IM -2262 and
IM -2264 measurement functions are fully protected from
overloads. The do and ac current ranges (except the 10A
range) are protected by diode
and fuse circuits, with an easily
accessible fuse. A resettable
rear panel circuit breaker provides protection on current
measurements from 200µA to
2000mA, making fuse replacement for moderate overloads
unnecessary. Resistance ranges
are electronically protected to
350V (peak). Floating measurements up to 500V (peak) from
earth (power line) ground can be
made with the unit's fully
isolated circuitry.
Both the IM -2262 and
IM -2264 operate on six carbon zinc, alkaline or nickel -cadmium
batteries (not included), or on
120Vac, 60Hz power with the
optional Heathkit PS -2404 bat-
tery eliminator. Both in-
struments also have a battery
test circuit, a low -battery indicator and a circuit to recharge
nickel -cadmium batteries in 24
hours (when the unit is off).
Circle (116) on Reply Card
48
Electronic Servicing & Technology
September 1982
IT
HAS
B&K
Precision
B&K Precision has added two
digital multimeters to its line of
DMMs for lab or bench work:
the 2801 and 2805.
Model 2801 is a 31/2 -digit
DMM for field, shop and hobby
applications. The unit takes advantage of the latest IC and
display technology to achieve
the lowest possible component
count, ensuring reliability, accuracy and stability.
A 9V battery provides power,
and low -battery warning indica-
tion is automatic. It comes with
test leads, carrying case, operation manual and a spare fuse,
and it measures ac and dc
voltage, dc current and
resistance.
Ranges are 0-2, 20, 200 and
1000V for dc; 0-200V and
0-500V for ac; and 90-2, 20 and
200mA for dc current. Input impedance is 10MS2 dc and 200KO
on 200V range, 2M12 on 500V
range. Circuit protection is
± 1000Vdc or dc plus ac
on all ranges. Overrange is indicated when the range limit is
exceeded. The frequency
response is 40-500Hz.
The model 2805 offers auto zeroing to minimize set-up time
and 22 ranges spanning up to
1000Vdc, 10Aac and 20M. Highenergy fusing protects against
damage from high level transient signals and LSI integrated
circuit technology reduces the
overall component count.
Ranges are 0-200mV; 2, 20,
200 and 1000V for ac and dc
voltage. The dc current ranges
are 200µA, 2, 20 and 200mA; ac
current ranges are 1000mA,
10A without shunt.
Input impedance is 10MO (ac
and dc) and circuit protection is
± 1000Vdc plus ac peak, 700V
rms Overrange is indicated
when range is exceeded, and
frequency response is 40-500Hz.
Circle (105) on Reply Card
FLY 691
-
FLY 692
NEW
Experience RELIABILITY! This flyback, designed
by THORDARSON, has
none of the problems
associated with this unit.
This new design uses the best
properties of both silicon and
epoxy.
There's MORE! THORDARSON'S unit has .convenient solder terminals not production type, wire wrap, terminals; providing a great
benefit when installing in today's new color chassis. All
THORDARSON'S fully integrated units have focus
capacitors in their circuits.
THORDARSON manufactures in one domestic location instead of various
foreign locations. Therefore
providing uniform tuning.
Ask your local distributor
for pricing and you'll discover
the total HAPPENING!
AVAILABLE NOW
THORDARSON
...design specialists of
electomagnetic devices
MT. CARMEL, IL. 62863
618 262-5121 TWX 510-525-2254
Circle (19) on Reply Card
Sep'ember 1982
Electronic Servicing & Technology
49
John Fluke
Manufacturing
can be stored as an offset, or
"relative reference." All subsequent readings are displayed
as deviations from the stored
reference. This feature is particularly useful when the absolute value of readings is less
important than the amount of
change. The relative function
greatly simplifies this type of
measurement by zeroing the initial value and displaying only
the positive/negative amount of
change on subsequent readings.
These relative reference
Fluke Manufacturing has announced a 41/z digit hand-held
DMM that should find its way
into toolkits of computer, communications and audio technicians. Engineering and calibration labs, where price and portability are secondary considerations, have relied on 41/2 -digit
multimeters to provide high
resolution and accuracy. But today, due to rapid increases in
the use of computer peripherals,
digital networks, telecommunications links and
video/audio transmission, there
is a need for precision high resolution measurements in the
field and shop.
The Fluke 8060A true RMS
multimeter fills this void in
hand-held instrumentation. The
8060A uses a 4 -bit microcomputer coupled with custom LSI
to go beyond traditional 5-function applications. Now, technicians can directly measure output frequencies of touch-tone
oscillators and audio amplifier
bandwidth with a hand-held
multimeter.
50
Electronic Servicing & technology
Two major components make
up the 8060A measurement
system: a 4-bit CMOS microcomputer and a custom CMOS
LSI chip. The heart of the chip
is a dual -slope analog-to-digital
converter and a digital control
logic section. The digital control
logic section includes a buffer
and decoder, read/write logic,
status and control registers,
and logic control for the continuity function. (The chip even
generates the continuity tone
indication by supplying a square
wave to the external piezoelectric transducer.) The microcomputer and the chip communicate
over a 4-bit bidirectional bus
and four control lines. The
microcomputer selects the appropriate measurement function according to the buttons
and switches depressed by the
user, and sends a conditioned
input signal to the LSI chip. The
microcomputer also controls the
measurement cycles, performs
calculations on measured data
and drives the LCD display.
Any reading on the display
September 1982
readings are also easier to
record and later manipulate for
test data verification.
When the unit is first turned
on, the microprocessor tests the
digital interface and illuminates
all LCD elements for 1.6s. Two
additional diagnostic tests can
be initiated by the ratio test and
a switch decoding test. The
ratio test checks the A/D converter for functionality independent of any input circuitry.
The switch decoding test indicates if the microcomputer is
interpreting each of the eight
switches and four push -buttons
correctly. The microcomputer
also monitors the internal (battery) power, and lights a display
(BT) when 80% of the battery
life has been expended.
The 8060A measures do voltage in five ranges: 200mV to
1000mV, all full scale. Input impedence, fixed at 10M12 in all
ranges, can be increased to
greater than 10,000M(1 in the
200mV and 2V ranges. This
allows nonloading measurements in high -impedance circuitry. The ac voltage measurement capabilities are also found
in five ranges to 750V RMS.
The true RMS monolithic converter provides accurate voltage measurements of nonsinusoidal waveforms. Displayed ac
readings can be in volts, relative
dB, or in dB referenced to 60011
The instrument computes these
dB readings from the linear
voltage reading by a segmented
curve matching algorithm. This
means of dB calculation is more
accurate than the traditional log
conversion, that is usually
implemented in hardware.
Frequency readouts from
.
12Hz to 200kHz are provided in
four ranges, which are fully
autoranged under the control of
the microcomputer. Frequency
resolution is 0.01Hz in the
lowest (200Hz) range, and readings are updated at a once -per second rate. The ac voltage
function can be used to verify
sufficient voltage (20mV sensitivity to 20kHz) for a valid frequency reading. Because the
frequency function uses the
multimeter front end, frequencies at 750V are safely
measured.
The ac and do current measurements can be made from
0.01µA (10nA) to 2A in five
ranges. Resistance is measured
in a ratiometric mode, comparing the external unknown
resistance to an internal
resistor. All
resistance measurements from
0.0112 to 200k11 are low power
so that resistances can be
measured in -circuit. Output
voltage is less than 250mV and
will not turn on semiconductor
junctions. In addition to the
reference
four selectable resistance
ranges, the meter autoranges
from 100kI2 to 300M9.
The 8060A continuity function is user selectable for visual
(LCD)
or
visual/audible
(LCD/tone) indication to allow
checking of wiring and PCB
traces for shorts, opens or con-
tinuity without needing to
watch the meter. To check semiconductor junctions, a constant
current diode test function is
provided. There is even one
range of conductance, 2000nS.
The conductance function,
basically an inverse resistance
range spanning from 500142 to
10,000M1 is particularly useful
for making component leakage
measurements or checking the
conductivity of fluids and solids.
High -voltage probes, high-frequency probes and a variety of
cables and adapters are available. Two optional temperature
probes convert the 8060A into a
direct-reading (C or F) digital
thermometer. Power is supplied
by a common 9V alkaline battery or an optional battery
eliminator.
Circle (114) on Reply Card
New
Beckman
VaIuePIusTM
DMM's
Instruments
B&K-PRECISION
gives you more
value than ever.
B&K-PRECISION's new Value+Plus
DMMs give you outstanding performance and price, plus extras you'd ex-
The HD-100 from Beckman
Instruments is waterproof and
dustproof to resist the
elements and can withstand the
physical impact of accidental
drops.
Voltage inputs are protected
to 1500Vdc or 1000Vrms. Current ranges are protected to
2A/250V, while resistance
ranges are protected to 500Vdc.
The 0 -ring -sealed ABS plastic
case is fire retardant, with
ribbed side walls.
The bright "NATO" yellow
case is highly visible - easy to
spot in a tool box or before leaving a job. Inside, the electronics,
including the "large area" LCD
and battery, are shock -mounted
to resist damage from impact.
A 9V alkaline battery provides up to 2000 hours of continuous operation and up to two
years of life under normal
operating conditions.
The single rotary switch
allows you to quickly switch to
the function and range you are
seeking.
A visual continuity test function called Insta -Ohms enables
you to check electrical continuity with the speed and ease of an
analog-type multimeter. In any
resistance range, an ohms symbol (il) appears in the LCD when
continuity is detected.
Each HD -100 comes with a
1 -year limited warranty, and a
complete line of Beckman accessories are also available for
use with the HD-100. They include a clip -on vinyl case, two ac
current clamps, a deluxe test lead kit, an RF probe and a high
voltage probe.
pect to pay more for.
The new 2801 and 2805 DMMs are compact 31/2 -digit instruments, featuring LCD
readouts, auto -zeroing, auto -polarity,
ten megohm input impedance and full
overload protection.
+Plus extras, at no additional cost, in-
clude high-energy fusing for added
safety, low battery indicator, durable test
leads and carrying case. Both offer rugged construction and LSI technology, for
long -life reliability.
Circle (107) on Reply Card
Model
2801
$65.00
Ideal for field service
Very compact -5.4" x 3.4"
Large 0.4" LCD readout
1% typical DC accuracy
x 1.4"
200 mV to 1,000 V ac/dc voltage ranges
200 µA to 10 A ac/dc current ranges
0.8% typical dc accuracy
Measures resistance to 20 Mfg
Value+Plus DMMs are available for
immediate delivery at your local
B&K-PRECISION distributor. For
additional information or the name
of your local distributor call
1-800-621-4627
DYNASCAN
NONEC/S/ON CORPORATION
6460 West Cortland Street
Chicago, Illinois 60635.312/889-9087
Intl SIs.6460 W. Contlend SI., Chicago, R 60635
Canadian Sales; Atlas Electronics. Onlarlo
South and Central American Sales.
Empire Exporters. Plainview, NY 11803
Circle (20) on Reply Card
September 1982
Electronic Servicing
&
Technology
2
51
Hewlett Packard
Hewlett-Packard has announced its first instrument
that combines signature analysis (SA), frequency -
counter and digital -voltmeter
functions with complete HP-IB
(IEEE 488) programmability.
Designed for manufacturing
and field service areas, the HP
5005B signature multimeter
provides a technique for faster
and more thorough testing of
digital products.
All front-panel functions and
measurements are completely
HP-IB programmable. The programmability provides auto-
mated controller -prompted
troubleshooting. Its advantages
include faster troubleshooting,
high productivity and the use of
lower-skilled operators.
This new rack -and -stack
measurement tool has a feature
set including 10 measurements
for digital troubleshooting.
Two modes of SA for simplified, component-level fault
isolation in synchronous digital circuitry.
Time interval and totalize
measurement capabilities to
check the various portions of
asynchronous digital circuitry
in a product.
A 50MHz frequency counter
to verify critical clock circuitry.
A 41/2 -digit dc and differential
voltmeter to measure power supply voltages and voltage
drops within a circuit.
An ohmmeter to verify circuit continuity and shorts.
A peak -voltage measurement
function to check the logic high and logic -low voltages of
active digital signals.
A single multifunction probe
within the HP 5005B enhances
digital -troubleshooting productivity because the 10 separate
52
Electronic Servicing & Technology
measurements can be made
without changing probe or
equipment connections.
All signal multiplexing to the
various measurement functions
is done automatically inside the
HP 5005B. With a small switch
located on the probe, an
operator can trigger all
measurement functions.
Completion of a measurement
is indicated by a programmable,
dual -volume, audible -alarm
beeper. This direct feedback im-
proves the measurement efficiency of an operator during the
troubleshooting process.
The 25MHz clock rate extends
the power of SA into higher performance digital assemblies.
Faster fault isolation can be
achieved through the use of the
qualified mode of signature collection. This mode helps isolate
faulty nodes by enabling
signature collection only while
specific test conditions exist. A
fault now can be isolated
systematically without modifying the test -stimulus routine.
Another important feature is
the ability to select one of three
preset logic thresholds (TTL,
ECL or CMOS) or a variable
threshold level (-12 to + 12V).
This threshold-selection flexibility ensures coverage of both
current and future logic
families.
Circle (117) on Reply Card
Hickok Electrical Instruments
The MX series of digital
multimeters, from Hickok Electrical Instrument Company,
provides 0.1% basic accuracy,
10MSE input impedance and
overload protection.
The premium version, the MX
333, contains two unique
features. They are the Vari Pitch, a built-in audible signal
that changes frequency in proportion to digital readings, and
Logi-Trak, a self-contained
logic testing capability that
combines the features of a high
performance logic probe and
voltmeter in one function.
Vari -Pitch functions on all
voltage, current, resistance and
diode test ranges. Audio
response is instantaneous, proportionate and accurate for
rapid indication on repetitive
measurements. Wide -range
audio output on each selected
range provides excellent audible
resolution. Thus, with a little
practice, the operator can
literally "troubleshoot by ear"
without taking his or her eyes
off the probe or waiting for
digital readings to settle.
On resistance measurements,
September 1982
lower readings (e.g. continuity)
produce the highest pitches. On
volts and current ranges, higher
inputs produce higher pitches.
Vari -Pitch also responds to inputs above overrange and can
be turned on or off for any
range or function, with no effect on the accuracy of digital
readings. It even provides
analog-like audible response to
variations for quick and easy adjustments and nulling.
Logi-Trak is a built-in logic
testing capability that combines
the features of a highperformance logic probe and
voltmeter in one convenient
function. It is activated by
pressing a logic button on the
MX 333. This automatically sets
the Vari -Pitch tone range for
maximum audible resolution of
logic level voltages and sets the
multimeter to provide direct
display of the actual voltage
(0-19.99V). Any 10:1 high -frequency scope probe may be
plugged into the safety -
insulated BNC input for measurement of all logic signals and
do voltages from 10mV to 20V.
It is also used to find logic
CSC
Electronics
The GC Electronics digital
multi -tester is designed to meet
the growing need for a rugged,
portable tester to help speed
field servicing on the growing
number of sophisticated digital
electronics systems in large appliances, video games and home
entertainment systems.
The tester features dual dial
settings that combine for a
26-range capacity, ± 2% do vol ,age accuracy, lA capability,
10Mß2 input impedance and a
31/2 -digit
SEMICONDUCTORS
display.
For added safety in case of accidental overload, all current inputs feature fuse protection.
Circuits are designed to prevent
nuisance fuse blows in voltage
and ohm ranges.
The anit operates on a standard 9V transistor radio battery
and a spare battery compartment lets you keep an extra battery handy for easy replacement in the field. A low battery
indicator warns you before the
battery power drops below a
critical level (approximately 3
hours of battery life remaining).
This
meter
measures
6"x33/4"x11/2" and weighs 12oz,
making it easy to carry in its
hard -sided carrying case. But
despite the small size, large
rotary selector switches allow
for easy, positive range selection with either hand.
Circle (115) on Reply Card
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36 CHANNEL CABLE
pulses as narrow as 5ns.
Variable pitch audible
response provides accurate indications of logic levels, with
greater precision than the
high/low thresholds of an ordinary logic probe. Marginal
and faulty logic states such as
shorts and opens are readily
identified through variations of
pitch. Square waves, pulse
trains and individual pulses are
identified by characteristic
sounds. And, because audible
response permits pulse detection with a minimum of attention being paid to the instrument, pulse memory is unnecessary. Using the digital
readout only for verifications,
the operator can perform logic
troubleshooting without taking
his eyes off the circuit.
Hickok MX -Series multi meters are designed to provide
maximum accuracy and convenience when used on a bench, in
the hand or even attached to a
belt. The rugged construction,
with suspended PC boards in a
high -impact plastic case, compact size and unique sloped
display make this possible. Belt
clips are furnished with the
units, and safety test leads plug
into the side so they are out of
the way and resist pull out.
Circle (118) on Reply Card
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in PA Call Collect 215-472-0369
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Circle
September 1982
(7) on
Reply Card
Electronic Servicing
&
Technology
53
Leader
Instruments
Weston
Instruments
óäò
-
curacy, wider bandwidth, and
lower cost of its average responding ac voltage and current ranges.
The model 6502 standard
features include six versatile
computing functions not
available on similarly priced
competitive instruments. A
total of 14 push -buttons, comLeader Instruments Corporation now offers a 31/2 -digit digital multimeter that fills the
need for both laboratory and
field work. The LDM-855 offers
automatic ranging, semi-
automatic zeroing and a large
LCD display for hands -free
operation.
When manual range or function selection controls have
been changed, a momentary
audible tone is heard. When
used in the resistance mode or
for checking continuity, the
tone is sounded continuously
when short-circuit conditions
occur. This enables the operator
to make tests without having to
constantly look at the meter to
see if continuity is present.
Other features include an
automatic polarity indicator, ac
and do measurement functions,
a LO -OHM mode to provide a
lower test voltage and a low battery warning incorporated into
the LCD.
The do voltage range is 0.1mV
to 1000V with an accuracy of
± 0.5% of reading ± 0.2% full
scale on the 0.2 to 200V range.
On the 1000V range, input impedance is 10MSl,overload protection is 1000V do and ac peak.
The ac voltage range is lmV
to 1000V. Accuracy for the 2V
range is ± 1% reading ± 0.4%
full scale at 40 to 500Hz. At 0.5
to 1.0kHz, accuracy is 1.5%
reading ± 0.4% full scale. On
the 20 and 200V ranges, accuracy is ± 1% of reading ± 0.25%
full scale for 40 to 500Hz, and
± 1% of reading ± 0.25% full
scale for 0.5 to 1.0kHz. On the
1000V range, accuracy
measures in at ± 1.5% of
reading ± 0.25,% full scale at 40
to 500Hz. Input impedance is
10MS1 and overload protection
is 1000V rms.
Circle (121) on Reply Card
54
Electronic Servicing
&
Technology
Weston Instruments has announced the availability of the
new model 6502 "educated"
digital multimeter. This
41/2 -digit, 5 -function
DMM is de-
signed for applications that can
benefit from the higher ac-
Triplett
Corporation
bined with a self -prompting display, provide flexibility in the
manipulation and recording of
data. Two storage registers
allow a display to be scaled by
any slope and offset. A single
NULL key stores a display as a
"zero" value and automatically
subtracts this value from all
subsequent measurements.
Two keys store any entered
polarity, auto -low battery and
auto-overrange indication, and
both hi and low power ohms.
It is designed for electronic
and electrical test and measurement uses, such as circuit
design, field service, production
and maintenance work, voca-
tional technical training
schools,
A new addition to its "true
hand -size" DMM line, the
Triplett model 3400, type 2,
31/2 -digit, 24 -range digital
multimeter features improved
basic do accuracy to 0.15%; ac
do voltage measurement to
1000V; 500-hour typical battery
life and improved overload protection on all volt and ohm
ranges to 1000V without fuse
blow, plus protection to 600V on
current ranges.
The 6 -function, batteryoperated test instrument also
provides additional features
all
such as auto -zeroing,
September 1982
auto -
television and communications equipment repair
and other applications.
The hand -size DMM has a
1/2 -inch LCD display providing
three readings per second at a
full range of 1999 counts and a
single dial range and function
selector. The ON/OFF switch is
also part of the range switch.
Overrange indication is vividly
shown to the user by the DMM's
display going completely blank
except for the 1/2 digit.
Polarity is displayed during
the overrange condition, and
three readings per second is the
reading rate for the test instrument. A 2A, 600V fuse is provided in the unit for current
ranges.
The unit weighs 10oz with
battery and comes complete
with a 1 -year warranty, 36 -inchlong test leads, screw -on insulated alligator clips, a wire tilt
stand, 9V battery and instruction manual.
Circle (132) on Reply Card
value as a reference and display
future measurements as a
percentage deviation from that
value. High and low limits can
also be stored and a LIMIT key
then allows the display of values
within these limits, or HI and
LO annunciators if the
measured value is outside of the
limits.
A START key initiates the
continuous storage of maximum
and minimum values. Pressing
a MAX key displays the maximum value, without disturbing
the continued accumulation of
values, and a MIN key similarly
displays the minimum value. A
RESET key allows the instrument to temporarily return to
the normal DMM mode without
losing any programmed com-
putation.
A FILTER mode activates a
binary weighted average of the
last four measurement conversions, assuring more accurate
and stable readings in the
presence of noise. To assure a
rapid response to step changes,
the filter function is
automatically inhibited when
sinewave. Full-scale decade
voltage ranges of 200mV to
2000V are provided with an accuracy of 0.2% ± 10 digits to
200V (0.5% ± 10 digits, to
2000V) over a 50Hz to 10kHz
bandwidth; accuracy is 0.5%
± 15 digits over the full band-
successive conversions differ by
more than 2% of full scale. All
computing functions may be
operated singly or chained, if
desired, to perform more complex multiple operations.
The average -responding
detector of model 6502 is
calibrated to display the
width of 30Hz to 20kHz. The ac
current ranges are 200µA to
2000mA full scale with a
midrange accuracy of 0.3%
± 10 digits.
The model 6502 also provides
do voltage ranges from 200mV
to 2000V, with constant 0.03%
± 2digits accuracy, do current
ranges from 200µA to 2000mA
and resistance ranges from
2002 to 20M(1.
equivalent RMS value of a
Circle (135) on Reply Card
For more in formation
on DMM p roducts...
Optoelectronics
Circle (124) on Reply Card
Sentore
Circle (125) on Reply Card
Sinclair
Although every effort has been
made to ensure completeness
and accuracy of this listing, the
publishers cannot be held
responsible for omissions.
Extech International
Alco Electronic Products
GC Electronics
Circle (104) on Reply Card
B&K Precision
Circle (105) on Reply Card
Ballantine Labs
Circle (106) on Reply Card
Circle (126) on Reply Card
Circle (113) on Reply Card
Simpson Electric
John Fluke Mfg. Company
Circle (127) on Reply Card
Circle (114) on Reply Card
Soar Electronics
Circle (128) on Reply Card
Circle (115) on Reply Card
A.W. Sperry
Heath Company
Circle (129) on Reply Card
Circle (116) on Reply Card
Systron-Donner
Hewlett-Packard
Circle (130) on Reply Card
Circle (117) on Reply Card
Tektronix
Beckman Instruments
Circle (107) on Reply Card
Hickok Electrical Instruments
Circle (131) on Reply Card
Circle (118) on Reply Card
Triplett Corporation
Boonton Electronics
Circle (108) on Reply Card
DeForest
Circle (109) on Reply Card
Data Precision
Circle (111) on Reply Card
Data Tech
Circle (110) on Reply Card
Dumont Laboratories
Circle (112) on Reply Card
Julie Research
Circle (132) on Reply Card
Circle (119) on Reply Card
VIZ Manufacturing
Keithley Instruments
Circle (133) on Reply Card
Circle (120) on Reply Card
Universal Enterprises
Leader Instruments
Circle (134) on Reply Card
Circle (121) on Reply Card
Weston Instruments
Mura Corporation
Circle (135) on Reply Card
Circle (122) on Reply Card
Workman Electronics
Non -Linear Systems
Circle (136) on Reply Card
Circle (123) on Reply Card
September 1982
Electronic Servicing & Technology
55
Previewing
the GE 1983 line
By Carl Babcoke, CET
General Electric's 1983 line of
TV and video products was shown
to a group of electronic -magazine
writers and service-association officials at the Portsmouth, VA, GE
factory on May 7, 1982. In addition
to the usual product -line general
information, new electronic cir-
cuits and other advanced features
were discussed and demonstrated.
Portable combinations
Road Show Portable Entertainment Center is the large name for
three small GE combination television, FM -stereo, AM-radio and
stereo-microcassette tape recorder/player machines.
Model 3XM3214E (Figure 1) has
a vertical format with front mounted controls. Black -and white TV programs are viewed on
a 3 -inch screen. The microcassette
recorder is not removable.
Step-up model 3XM3226X has
the same basic features in a
horizontal format with most controls on top. In this unit, the
capstan -drive stereo microcassette
recorder can be removed for external operation, powered by two
AA batteries. Two condenser
microphones allow recording in
monaural or stereo. When the unit
is operated outside of the combination, playback is possible through
stereo headphones, which are supplied. Of course, when the
recorder is plugged into the combination, all tape sounds are heard
through the two stereo speakers.
Notice that the microcassette
format has very small cassettes
that are not interchangeable with
conventional audiocassettes. Prerecorded music tapes in microcassettes are becoming available, or
blank tapes in 15-, 30-, 45- and 60-
minute lengths can be recorded by
the user.
Model 4CM3326X (Figure 2) has
a 4 -inch color picture tube in addition to the FM-stereo, AM -radio
and detachable microcassette recorder (as described previously.)
TV receivers
More than 50 new color TV receivers are offered in the 1983 GE
line, including three 10 -inch, four
13 -inch, 11 19 -inch, 31 15 -inch,
one 4 -inch (previously described)
and two projection models. Three
12 -inch and two 3 -inch b&w
models also are offered. One of the
high -end 19 -inch color receivers is
shown in Figure 3.
About 70% of the color receivers
have quartz-controlled electronic
tuning, and about 50% have
remote control (Figure 4). Four
types of channel-selection systems
Figure 1 M>del 3XM3214E from General Electric for 1983
has a 3-inci bdow television, FM -stereo and AM -radio
reception, pus a stereo microcassette recorder/player. A
step-up mocel pith similar general features permits the
microcasse?:etc be removed when desired for headphone
listening wh le.ogging.
Figure 2 A 4-inct color television is th: main
feature of 13E model 4CM3326X, which aso has
FM -stereo and Atviradio reception and a removable nicrocassatte recorder/playe-. Lightweight headphones are included for the microcassette machine.
are included. These are explained
later in the technical section.
Receivers with the dual -mode
keyboard/scan tuning system have
a feature called Channel Block -Out
that allows elimination of any
channels for up to 12 hours. For
example, if a parent is to be
away from home for the evening,
but wants to prevent the children
from watching an X-rated cable
program, that channel can be
deleted by keying in a certain code.
Any of the 112 channels can be
eliminated. Restoration of the
channel is automatic after 12
hours, but it can be brought back
sooner by again keying in the same
code. This feature is in 12 19 -inch
and 25-inch models.
Color Monitor (automatic color adjustment circuit) is in 18 models
from 13 -inch to 25-inch color receivers. The VIR system is in five
19 -inch and 18 25-inch models.
This system automatically adjusts
the color saturation and hue according to the vertical -interval
reference (VIR) signal that is included in many broadcast signals.
Owners of VCRs or videodisc
players need convenient storage
space for this extra equipment.
Figure 3 Model 19PC3744W is General Electric's tcp-of-.he-I,ne 19 -inch color TV
receiver. Some features are VIR Broadcast -Controlled color, Color Monitor
Room -Light Sensor, Programmable Scan Remote Control, Quartz Electronic Tun
ing with 112 channels and digital channel readout, and other features of the PC
chassis.
Figure 4 Random access and up/down channel scanning
are both possible with the remote control at left. Power
on/off, up/down volume, and the programming of active
channels can be done with this remote. GE models with
Favorite -Channel Programmable Scanning can be pro
grammed from the remote (right). All but the mechanical tuner models have PLL-type electronic tuning.
when connected to a stereo-signal
source.
Two large -screen projection color receivers in the 1983 line are
the Widescreen-1000 and the new
compact version, the Widescreen40, with a 40 -inch rear -projection
screen (Figure 6). The cabinet of
the new version is only 36 inches
wide, 24 inches deep and 45 inches
high. Three 5 -inch projection tubes
provide maximum brightness,
while other top -of-the -line features
include a comb filter, VIR color
control and infrared remote control for 112 channels, Channel
Block -Out, full video and audio
jack pack, and dual -channel
Figure 6 New for 1983 .s the GE Widescreen-40, which has a 4-inch -diagonal rear projection screen and three projection picture tubes. An optional cabinet for storage
of audio and video accessories matches the size and appearance, as shown.
Widescreen-1000 (1000 square inches) is continued in the GE line.
amplifiers for stereo sound from
videodiscs or VCRs that have
stereo signals. An optional storage
cabinet is available in size and
style to match the television.
Two cabinet styles in the Video Classics Collection are offered.
One hides the video equipment
behind a roll-top, while the other
(see Figure 5) has contemporary
styling with a glass door. These
Videocassette recorders
Four table -type VCRs are in the
new GE line. All are 8-hour VHS
models with electronic TV-station
tuning of VHF channels (some
have four UHF channels, also) and
a digital clock display that
25 -inch models have a full jack-
pack for easy direct connections of
VCR, videodisc or a separate audio
amplifier. Internal dual -channel
amplifiers and dual -speaker
systems allow true stereo sound
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ECG238
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ECG REPLACEMENT TRIPLERS
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Auto Reverse Cassette Head
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AN16Trinitron Dual Ant. for Sony
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ADC MARK III CARTRIDGE wlneedle-min. 3
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800-860 Zen. Safety Cap
$ 3.95
Quantity Prices Available
Letters of credit and all checks placed on deposit with Bank of Hallendale,
FL. VISA & Master Charge accepted. Min. order $75. FOB Dania, FL.
Catalog $3, refundable upon order.
SEND CHECK OR MONEY ORDER TO:
OPTIMA ELECTRONICS
2022 Tigertail Blvd., Dania, FL 33004
Phone (305) 920-3550 TOLL FREE: 1-800-327.0224
Circle (22) on Reply Card
www.americanradiohistory.com
operates with the station programming. Model 1VCR3000X has a
10 -day programming
1 -event,
feature and a remote-operated
pause control. Model 1VCR3010X
(Figure 7) has 3 -event, 10 -day programming plus a 9 -function wired
remote control. The Model
adapter fits into the
battery compartment. Five types
A special ac
of power can be used.
Because portable VCRs normally do not include TV tuners or
timers, two optional tuner/timer
units are offered for use with this
model.
Color video cameras
Color camera models in the line
are
the
1CVC3030E
and
1CVC3035E. Both have an adjustable viewfinder, infrared automatic focusing, a fast f1.4 lens
with automatic iris
control,
variable -speed 6:1 power zoom,
1VCR3014W has similar features,
but with a program -search mode,
audio dubbing and 5 -event, 7 -day
programming. Top -of -the -line
model 1VCR3018W has four video
heads for special effects, wireless
remote control, a second audio
track for stereo -sound applications, and 8-event, 3 -week programming.
Model 1CVD3020X is a VHS
lightweight portable VCR with a
rechargeable battery for up to 100
minutes of recording between
charges. Weight with battery is
only 81/2 pounds. Features include
three speeds for up to 8 hours of
recording/playing per tape, special
effects in the EP mode, freeze
frame with frame -by -frame advance, video scan up to nine times
normal speed, and an LCD digital
tape counter with memory search.
Figure 7 For 1983, the GE line includes four videocassette recorders and one portable. Pictured is model 1VCR3010X, which has 3 -event, 10 -day programming with a
9-function wired remote control. All VCRs are VHS types capable of recording for 8
hours maximum per cassette.
Chus
FINALLY. COMPUTERS AS A
NEW TOOL FOR T.V. REPAIR.
Primefax puts computer -assisted repair capabi ity in your shop today.
Primefax drastically reduces the
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trouble-shooting procedures.
Through the use of today's techReduced call backs faster turnnology. Primefax maintains-in a
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Primefax is a compilation of the
The more Primefax is used, the
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In Texas, call (512) 344-5999
TECHNOLOGY
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48 Farrand St., Bloomfield, N.J. 07003
(201) 429-0855
4825 Fredericksburg Road
INC.
San
(800) 526-1374
Antonio. Texas 78229
Circle (23) on Reply Card
Circle (24) on Reply Card
September 1982
Electronic Servicing & Technology
59
used to insert titles or comments
on any scene during recording.
Technical details
Figure 8 This is a closeup photograph of the operating controls on the 1CVC3035E
GE color camera. Functions of fades, character generator and stopwatch are controlled by push -buttons. The portable VCR can be started and stopped from the
camera.
macro -focusing to
1
inch,
automatic white -balance control,
extendable boom microphone, tally
lamp, shoulder rest and a standby
power switch.
Also, model 1CVC3035E has a
Newvicon camera tube, fade-in or
fade-out control, CRT viewfinder,
character generator, stopwatch
with on -screen readout, and a
positive/negative switch for
recording color negatives or slides.
A panel on the shoulder rest
(Figure 8) has push-button switches for camera and VCR control.
The character generator can be
The three new chassis are PC,
25PC (for larger screen models)
and PW for the Widescreen-40
projection model. The PC chassis
replaces the former EC in most
19 -inch color receivers.
One interesting circuit function
in the PC and 25PC chassis is the
+ 116V power-supply regulator
that indirectly regulates the picture width and high voltage. Previously, the EC-chassis regulator
used the collector -to -emitter path
of a power transistor as a variable
resistance to develop a voltage
drop (from the current). As the input voltage or the load current
changed, the circuitry forced the
transistor resistance to produce
whatever voltage drop was required to maintain a specific unvarying output voltage. Although
the voltage drop and load current
varied somewhat during normal
operation, they were relatively
constant. A transistor dissipates
power unless it is cut off or totally
Our lowest price
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For many years ADCO intercoms have been a leading
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communication under the most severe conditions.
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... many where conventional intercom systems failed totally.
Typical installations are in factory production zones,
on loading docks, and in other outdoor areas-in saw mills,
steel mills and foundries-on construction jobs and oil rigs.
Regardless of weather, temperature or operating conditions.
Each individual intercom unit is self-contained.
transmitting an amplified signal to permit an unlimited
number of stations over any distance. Installation '.s simple,
practical: plug each unit into a power source and connect
units together by ordinary 2 -wire cable.
Full range of AC and DC models available, as well
as extreme temperature models and units compatible with
existing sound -power systems.
ATKINSON
DYNAMICS
AUTOMAT®
PRODUCTIC N
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142 Peconic Avenue
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(:13) 654-1197 TWX: 510-228-2120
A Division of Guy F. Atkinsor Company
Section B
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South San Francisco, CA 94080
Phone (415) 583-9845
Circle (25) on Reply Card
60
People get suspicious when they see "lowest priced."
Especiall; it a precision piece of equipment. They
ir-medrately think it's garbage.
Despite the reasonable price our EX-525 gives you
vacuurr ty an oiless, piston pump not diaphram. It
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mul:i-layei PC boards. The EX -52E ccmes with a great
technical Manual and 2 year warranty
The E>-525 is inexpensive, but it isn't cheap.
Electronic Servicing
&
Technology
September 1982
Circle (26) on Reply Card
saturated. In the previous
regulator, transistor resistance
and the resulting voltage drop
never approached zero. This loss
produced a significant waste of
power as it added heat to the
chassis.
A different basic principle is
used in the PC -chassis regulator
circuit. Voltage regulation is obtained by variations of the time
duration that a filter capacitor receives replenishing charges of
power. In other words, it is
another way of producing a
specific dc voltage by using a
storage capacitor to integrate
pulses of do voltage. The general
method is shown in Figure 9.
Switching of the capacitor charging voltage in the PC
regulator is in the negative (rather
than the positive, as in the
simplified example), but the principle is the same. Figure 10 is a
simplified schematic of the PCchassis regulator. A silicon controlled rectifier (SCR) replaces the
relay contacts to provide rapid,
bounceless switching. Notice that
the triggering is synchronized to
Current
limiter
Load
Relay
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storage
capacitor
Figure 9 Regulation of high voltage and picture width in the PC chassis is accomplished by regulation of the + 116V supply for the horizontal -output transistor.
Variable (but not regulated) dc voltages can be produced by this theoretical circuit
(which is not the one in the PC chassis). When dc power is brought through a
constant -current or current -limiting device (an inductance is used here), and the duty
cycle of the relay -contact on time is varied, these pulses of dc voltage are integrated
by a sto -age capacitor into a filtered dc voltage equal to the average voltage of the
pulses. Of course, narrower pulses (shorter duty cycle) have a lower average voltage,
therefore, the integrated and stored voltage will be lower than that from wider
pulses. Although this block diagram illustrates the basic principle (variation in the
time duration of applied power), the actual GE regulator block diagram (Figure 12) is
different in details. For example, the on/off keying of input dc power is accomplished
by an SCR. Also, the keying is in the negative leg of the input power, not the positive.
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dc voltage
dc supply
800-526-4928
WRITE OR CALL FOR OUR 1982 PRICE LIST
DIGITRON ELECTRONIC
Corporation
110 Hillside Ave., Springfield, N.J. 07081
DIGITRON IS NOT ASSOCIATED IN ANY WAY WITH PHILIPS ECG
Circle (27) on Reply Card
Low cost tool for design
and trouble -shooting
Pocket Size
Slide -Switch
Resistance
Substitution Unit
still only
Over
11
$58
million step range
1% accuracy resistors
Unique in convenient size
Rugged construction
Small enough to take anywhere in your pocket, this aluminum housed unit delivers a very broad range of resistance steps.
Excellent for both development and repair work.
Half -watt 1% tolerance resistors give an accurate range from
1
to 11,111,110 ohms, in one -ohm steps. Has three binding
posts, one to ground case.
Available now from stock. Catalog No. 7092-236. Cash savings
available, see coupon. Write, or call (804) 264-7590. Phipps & Bird, Inc.
E Please send
Units (6 $58 each. (Check enclosed less 5%
cash discount)
Units (a) $58 each C.O.D. (Phipps & Bird will pay
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Name
Firm
Address
City, State
Zip
Ask your dealer, or contact:
pCI 0 pp0
W: ß5o oa¢o
O
Manufacturers of Scientific Instruments
P.O. Box 27324 Richmond, Virginia 23261 Phone: 804/264-7590
Circle (28) on Reply Card
September 1982
Electronic Servicing & Technology
61
PC -chassis
regulator
Several basic facts must be
clarified before the operation of
this GE circuit can be understood properly.
The do voltage in an integrating or storage filter
capacitor varies according to
duction is operating, the gate
voltage has no effect on the current. Therefore, the A/C path
current continues until the current is brought to zero or the
anode becomes at least slightly
negative relative to its cathode.
SCR903 conduction then passes
a negative voltage to the
grounded end of C904, the
storage capacitor. Maximum
current is limited by L909,
otherwise, the circuit would be
peak reading and little voltage
variation would be possible. Unless something stops SCR903
from conducting, the output
voltage soon would reach
+ 155V, the input supply
voltage. However, a flyback
+ 116V
+V
supply
C902
bridge rectifier
storage
Turn -on
+ pulses
330pF
155Vdc from
C904
100µF
Y963
filter
lam,
Pulses
from
'flyback
nnn
SCR903
Current
I
111
Turn-off
- pulses
Triggering
sensing
H
Sawtooth
control
Horiz
pulses for
sync
GE SCR rectifier
Figure 10 This simplified schematic of the PC -chassis regulator shows details
cuit regulation.
the width (duty cycle) of
current -limited dc -voltage
pulses that are applied to it (see
Figure 11). Well -filtered do voltage comes from the bridge rectifier and C902. L909 is the
current -limiting inductance,
C904 is the
storage or in-
tegrating bapacitor and
SCR903 is the electronic switch.
Secondly, an SCR (silicon controlled -rectifier) has a
regenerative action that allows
rapid and dependable switching
of considerable power. SCR
conduction must be initiated by
a positive gate voltage (relative
to its own cathode). After con62
Electronic Servicing & Technology
jf cir-
Notice that the switching
SCR is in the negative leg of the
+ 155V supply between hot
ground and chassis ground.
Voltage between the + 116V
supply and ground is monitored
by two transistors that form a
voltage sawtooth waveshape
whose slope varies in step with
the + 115V supply. The starting
of each sawtooth is initiated by
a pulse from the horizontal sweep circuit.
Conduction of SCR903 begins
when the sawtooth's instantaneous voltage reaches a level
that produces a triggering pulse
from the third transistor.
September 1982
§
Load
111
A
dc Voltage
LJ
limiter
I
i
Hot ground
L909
winding applies horizontal sweep pulses to the SCR903
anode and these pulses stop the
SCR903 conduction at the
center of each horizontal
retrace.
To summarize the action: Conduction of SCR903 is started
during each horizontal cycle at a
time (phase) determined by the
exact +116V supply voltage. A
lower voltage triggers the SCR
on earlier; a higher voltage
starts SCR903 conduction later
in each cycle. Conduction of
SCR903 is ended at the same
time in each horizontal cycle. A
low + 116V level lengthens the
conduction time of each cycle,
while a voltage higher than
+ 116V shortens the SCR con-
duction times. In other words,
the precise + 116V level is maintained by variations of the
SCR903 conduction times.
Incidentally, sudden cessation
of the SCR903 current produces
a voltage pulse across L909, so
diode Y963 has been added to
rectify these kick-back pulses,
thus making the regulation
more efficient and reducing the
ripple on the + 116V supply line.
The starting circuit is not
shown here; refer to the GE
schematic for those additional
components.
the horizontal -sweep frequency
and that negative -going horizontal
pulses are provided at the SCR
anode to stop its conduction at the
same point of each horizontal cycle. Other details of circuit operation are given with the Figure 10
schematic. This regulator reduces
the line wattage and the chassis
heat.
An interesting new component
is the flyback used in PC and 25PC
chassis. The windings are stack wound to give maximum protection against arcs and shorts while
allowing a smaller overall size.
Diode rectifiers are integrated
with the windings. Focus and
CRT -screen controls have thick film construction and are included
inside the overall insulation. The
flyback is mounted directly to the
circuit board.
A narrow-neck, black -matrix
picture tube with bi -potential guns
and fast-warmup cathodes is standard in all PC models. The
previous type of simplified convergence and purity is continued.
These new picture tubes have internal features that are said to
reduce the current of any HV arcs
to a fifth or an eighth of the arc
current in conventional tubes. This
should minimize CRT damage
from arcs.
The mini service manual (which
has been included in a rear -panel
compartment of GE color receivers for several years) is supplied again in the 1983 line. This
feature has been popular with
technicians.
A servicing position has been
provided for the chassis (Figure
11) to permit top and bottom
circuit -board instrument tests and
visual examinations. Copper wiring is on one side of the board only,
and this should enhance the
reliability as well as simplifying
the finding of test points.
haccic omnnnrÌ
NEW from RCA ... VGT 650
VCR Video Tape Program .. .
RCA
Technical
Training
Video Presentation
43`r_
VG
6wsion
Familiarization
and
Servicing
16
Ren
Video Tape
Full 150 -Minutes in Color
.
PLUS THESE FREE SERVICING AIDS
Workshop Manual ..
Training Workbook
.
...
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Servicing Procedures
Reinforces Your Learning
With "Hands -On" Exercises
Complete Package Only $79.95
Full-color Technical Training Video Tape (VHS Format) will prove
invaluable for technician training or for use at the bench when
the VGT 650 is being serviced.
Includes these specific audio and visual instructions on:
Two New Microprocessor
Dolby* Noise
Reduction System
Tape Transport Familiarization
Express Record Operation
Special emphasis on the new video and head switching circuits
which control such features as noiseless field still and field slow
motion operations.
Control Systems
Digital Controlled Servo
Systems
'Dolby, is a trademark of Dolby Laboratories Licensing Corporation
The most vital circuit areas are referenced to the VCR counter number so the technician can proceed directly to the related subject
matter on the tape.
System LMP91 also covers 82
TV -broadcast and nine cable channels, but it operates by scanning
up or down through all programmed channels in sequence.
Scanning and volume control can
be operated from the TV panel
Figure 11 Allen Nelson demonstrated many serviceability features of the new GE PC
chassis. The color receiver is shown on its side, with the chassis in the convenient
service position.
costly) damages to the test equip -
band and the divider ratio in the
'ed
tic
als
ed
he
ns
keyboard or the remote.
The KMP91 system provides
keyboard random selection of 91
channels, but has no remote control. AFT search for off-frequency
signals is initiated for each channel
selection.
Most 25 -inch models and a few
19 -inch models include one of the
following 112 -channel tuning systems. KMP112 is the GE state-ofthe-art electronic tuning system,
which is the basis for the other
three 112 -channel systems
(LMP112, SET112 and MP112).
Special resistors and capacitors
are used instead of conventional
ones. They are called chips because
they have no pigtail lead wires and
so are soldered directly to the circuit. The reduced component inductances contribute to the efficiency and stability of these
critical circuits.
The KMP112 has random access
to all channels only by the receiver
keyboard. There is no remote control feature.
SET112 has up-and-down scanning of all programmed channels,
without remote.
The LMP112 has up-and-down
channel scanning, similar to that
of the SET112, but with remote
control of all channels, including
programming.
MP112 has all features, including random access and scanning of programmed channels
(dual -mode operation) from the
receiver panel and also from the
remote -control transmitter. Other
push -buttons switch the power on
or off, and raise, lower or mute the
audio volume. This is the only GE
tuning system that includes the
30 -Dec. 2
October
Midcon/82 High -Technology
Electronics Exhibition and Con-
11-13
cALEIV OAR
OF EVENTS
EIA Fall Conference, Century
Plaza Hotel, Los Angeles. For
more information, contact the
Electronic Industries Association,
2001 Eye St., N.E., Washington,
September
vention, Dallas Convention
Center. Contact Electronic Conventions, 999 N. Sepulveda Blvd.,
El Segundo, CA 90245, 1-800421-6816 (in California, 1-213772-2965).
DC 2000e.
14-16
Wescon '82, Anaheim Convention Center, Anaheim, CA. For
more information call 1-800421-6816.
18-20
1-2
14-16
Mini/Micro Computer Conference and Exhibition, Disneyland Hotel, Anaheim, CA. Contact
Electronic Conventions, 999
Sepulveda Blvd., El Segundo, CA
90245,
January
November
1-800-421-6816 (in Cali-
fornia, 1-213-772-2965).
15th Annual Connector Symposium, sponsored by the Electronic Connector Study Group,
with the cooperation of more than
50 connector manufacturers,
Franklin Plaza Hotel, Philadelphia. Contact Electronic Connector Study Group, P.O. Box 167,
Fort Washington, PA 19034.
Southcon/83 High -Technology
Electronics Exhibition and Convention, Georgia World Congress
Center, Atlanta. Contact Electronic Conventions, 999 N.
Sepulveda Blvd., El Segundo, CA
90245, 1-800-421-6186 (in Califor-
nia, 1-213-772-2965).
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1
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Write or call for a full color descriptive catalog or the
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2 year warranty, all parts, labor
California residents call (213) 767-0044
SDLTEC®
CORPORATION
11684 PENDLETON STREET
SUN VALLEY, CALIFORNIA 91352
Circle (36) on Reply Card
September 1982
Electronic Servicing & Technology
65
Average or true RMS:
By Jim Smith, Sales Engineer, Sencore
Average RMS or true RMS:
Which ac voltage measurement is
the right one for you? Is one more
important, or are they equally important? These are typical questions asked by technicians across
the country.
the rectifier and meter are
average responding so the resultant reading on the meter will be
the average, or 63.7%, of the peak
voltage applied.
However, average ac has no real
meaning because it is not used in
The average-RMS
always give a different reading
than the true-RMS voltage when
you measure ac voltages that are
not a pure sine wave. This is why
. .£
most en
Per cot u{ Pea
100
10
60
--
--
wits
ValV.
-EFFECTIVE
'AVERAGE
: vp
PEAK
to
PEAK
40
Symmetrical Square
vFp
OHse, Pulse Wov
These questions are compounded
that meter manufacturers offer both types of ac voltage
measurements: average RMS in
one model and true RMS in another model. They leave it up to
you to make a decision as to which
meter you should purchase. It's not
that these manufacturers cannot
make up their minds; there are
good reasons for both types of
measurements. Let's take a look
at the two types of ac voltage
measurements and see what they
are, where they are used and
where they are important to you.
electronic measurements. The
average ac can be converted to
by the fact
What is average RMS?
Average RMS is derived by
measuring the average voltage of
a pure sine wave and multiplying
the results by 1.11 to obtain the
RMS value. This is based upon the
mathematical relationship between the two quantities in a pure
sine wave. Average ac voltage is
easy to measure with a bridge recfier an
d dc meter. Both
66
Electronic Servicing
&
Technology
RMS by multiplying by 1.11. Most
meters use average detection and
multiply the results by 1.11 with
an amplifier before applying it to
the digital readout, because it is
less expensive than a true-RMS
detector.
i king average detection and
multiplication to obtain average
RMS is acceptable as long as you
are dealing with pure sine waves,
such as the output of power transformers. However, if the sine wave
becomes distorted, or if you
measure other ac voltages, such as
a square wave or pulses, the 1.11
multiplier no longer holds true. A
good example of the error that can
be introduced can be seen when
you measure a square wave. The
average and the RMS values of a
square wave are equal. If your
DVM multiplies the average
results by 1.11, you will find that
the voltage you measure from the
square wave will be 11% higher
September 1982
0.3i85VFp
orp
orp
O.SVp.p
0.5Vp.p
T_N
_
Vpp=VpA
This simple circuit is used to measure
the average-RMS value of a sine wave ac
voltage.
0.353Vp-p
rVp Vp.T.(I.T)/.
,MWff
F- --y
pure sine wave showing the relationship of the RMS and average values in
percentages.
0.63TVp
2870
We,.
20
A
v.r.V.
AVOW.
0.707Vp
RNS.fp
N=a)
T_N
P
The comparison of the various
waveforms and how they relate to the
peak -to -peak,
RMS
and
average
ac
voltages.
that reads the true-RMS ac
voltage and not average RMS.
When measuring ac voltages
around the ac input and power
supply and comparing them to a
schematic, you must have average
RMS, because there is usu
some distortion in the
signal, with additional
added by the transforme
filters, etc. The original va
marked on schematics were to
with average RMS, and the
tion errors must be matche
the measurements that you
taking. If you use a tru
meter, your readings may n
respond to the schematic v
and will cause confusion. Y
not know if there is a prob
the circuit or whether the reading
differences are being caused by
your meter.
What is true RMS?
True RMS or root mean square is
defined as the effective value of an
ac voltage that will produce the
same heating effect as a similar dc
voltage. RMS is the square root of
the mean (or average) of the
squares of the instantaneous
values of the segments of the ac
voltage (or root mean square).
One way to measure the true
RMS of an ac voltage is to take the
sine wave or other waveshape and
break it into many segments. Each
segment of voltage is squared and
then added to the squares of all the
other segments. To find the
average squared value of the ac
voltage, divide the total of all the
segments squared by the number
of segments. The square root of
RMS =
+
V222
v..2
15
I
..2.10.
I
12.N.14,15
To measure true RMS, you must break
the waveshape into small segments,
square these instantaneous voltages,
average them together and
square root of the result.
this value is the RMS value.
IMathematically, true RMS is
70.7% of the peak value of a pure
sine wave. In a square wave, the
RMS value is 50% of the peak -to peak, and in a triangular wave, the
RMS value is 57.7% of the peak
value. True RMS for non-regular
waveforms is not a simple mathematical deriva:ion of the peak of
the ac voltage and depends upon
Your ad
gets quick
results.
Advertise
in
classifieds.
the peak amplitude as well as the
overall shape and time duration of
the voltage.
True RMS requires a more complex and expensive circuit to convert the ac voltage being measured
into its RMS value than used by
average -detecting meters. These
complex circuits are generally
combined into a special IC called
an RMS converter. These ICs are
not found in most DVMs due to the
high cost of the IC itself. Some
more expensive models may include the RMS converter IC, but
do not include the average detection circuit to provide you with
both types of ac measurements.
True-RMS ac voltage measurements are important when you are
dealing with power delivered to a
load. One example is in the newer
TV sets and video monitors using
scan -derived CRT filaments. The
CRT filament is heated with a
pulse taken from a winding on the
flyback transformer. This pulse
should be measured with a trueRMS meter to be sure that the
voltage applied to the CRT is producing the required 6.3V of RMS
heating energy. If the voltage is
measured with an average-RMS
meter, the readings may be
anywhere from 3.5V to over 8V,
depending upon the meter used.
The horizontal output transformer of a TV set is a type of
switching power supply. Switching
power supplies of this type can be
found in many apflications, such
as radar, video monitors and computer displays. Most of these will
heat the CRT filament with a pulse
from the switching power supply
transformer, making the ability to
measure for true RMS important.
There are many other applications
that use non -sinusoidal signals and
require true-RMS measurements
to determine the heating effects of
this signal, such as motor controls
and heating elements in dryer
systems. True-RMS ac voltage
measurements are the only answer
for these applications, because
average-RMS measurements will
give incorrect readings of the
distorted ac voltage waveforms
present.
Which RMS measurement?
There is no correct answer to
this question because we are in a
period of transition. Service
literature published during the
past 30 years will generally be
referenced to an average-RMS
meter, whether or not the
readings represent the actual
power delivered by the circuit.
Much new literature is beginning
to show values referenced to true
RMS, and the average -reading
meters will show an error when
making measurements here. In addition, we must face the fact that
more and more of the signals encountered in power supplies are no
longer sine waves. Switching
power supplies, flyback -powered
circuits, and SCR or TRIAC controlled supplies are becoming commonplace in almost every industry
and none deliver sine waves.
Both average and true-RMS are
important in order to work with
the circuits of the '80s and not
restrict applications in older circuits. Some DVMs offered today
make it possible to measure both.
MAKE SURE you get paid for every
inch of wire sold
EXACT MEASURING is a must when
you retail coaxial cables, audio
cables, and electronic/electrical
wires. You can work confidently and
quickly ... yet keep close control ...
with HYKON WIRE METERS and
REELS set up on a counter or as a
portable combo. Wire up to 1" diameter pulls from stock through the
meter onto take-up reel for neater
delivery. Write for details or call us at
AREA 216 821.2320
MANUFACTURING
Post Office Box 3800 -ET
Circle (29) on Reply Card
September 1982
CO.
Alliance,
OH
44601
Electronic Servicing & Technology
67
ATTENTION
TECHNICIANS
*
JOB OPENINGS
*
MONTHLY TECHNICAL
NEW
PRODUCTS
TRAINING PROGRAM
*
BUSINESS MANAGEMENT
TRAINING
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LOW COST INSURANCE
Tool case
The Tranny Caddy T10 weighs
11 pounds when empty, and has
clear plastic lids and a lift -out tray
inside. Features include reinforced
Pin tip probe
CERTIFICATION
A flexible pin tip probe has been
TECHNICAL SEMINARS
developed by ITT Pomona Electronics. The probes, available in
three models, are made of brass
with gold-plated tips. The probes
All of this in
a nonprofit
international association
for technicians
FIND OUT MORE:
hinges and riveted polypropylene
construction. The case is available
from MHP (Medical & Hospital
Products).
Circle (71) on Reply Card
R.R. 3 Box 564
Greencastle, IN 46135
J
attach easily to the ends of the ITT
Pomona Electronics line of test
probes.
Circle (66) on Reply Card
Now, more than ever
...Men who KNOW say...
IS THE ANSWER
5 -way binding post
OK Machine and Tool Corporation has just introduced its new
"BP" series of binding posts.
Equally suited to amateur and in-
dustrial applications, the binding
post can accept a phone plug,
banana plug, alligator clip, spade
lug or wire strands directly.
Mounting hardware supplied in-
SINAD distortion voltmeter
HF Signalling model 826
SINAD distortion voltmeter is a
combination SINAD distortion
meter and ac voltmeter that can be
taken anywhere. Just connect
receiver audio to the detachable
shielded input cable and read
The
SINAD distortion directly,
because there are no frequency,
null or level adjustments to make.
It is also an accurate audio ac
voltmeter with nine ranges from
HELP NATESA HELP YOU
BY
DOING YOUR PART
Are YOU the operator of an
ethical, professional caliber tv radio -home electronics service
business?
Write for details on how you can
gain great benefits and participate
in the destinies of this great
industry.
NATESA
5930 S. Pulaski Road
Chicago, Illinois 60629
cludes plastic washers for complete insulation from PC board or
chassis. Available in red, yellow,
green and black, the binding posts
are offered one of each color to a
package for amateur or lab applications, and 100 of one color to a
package for industrial volume
users.
Circle (65) on Reply Card
68
Electronic Servicing & Technology
September 1982
10mV to 100V full scale and allows
the user to check audio levels from
the microphone to the speaker,
easily and quickly.
Circle (57) on Reply Card
Antenna and amplifier packages
Two combination antenna and
preamplifier packages have been
added to the Winegard line. The
amplified outdoor antenna
packages are the PR -8687, which
PAT.
N
4,259,705
WARNING!
Electric Power
Pollution,
Spikes,
Interference
includes Winegard's Prostar
PR-860 VHF/UHF/FM antenna
with the GA -8700 high -input
&
Circle (79) on Reply Card
Our patented ISOLATORS eliminate
equipment interaction, curb damaging
Power Line Spikes, Tame Lightning bursts
& clean up interference.
Isolated 3-prong sockets; integral Spike/
Lightning Suppressor. 125 V, 15 A, 1875 W
Total, 1 KW per socket.
ISO -1 ISOLATOR. 3 Isolated Sockets;
Quality Spike Suppression; Basic
$69.95
Protection
3 DUAL Isolated Sockets; Suppressor; Com$104.95
mercial Protection
ISO-17MAGNUM ISOLATOR. 4 QUAD
Isolated Skts; Suppressor; Labora$181.95
tory Grade Protection
ISO-3 SUPER-ISOLATOR.
varieties of satellite reception
course, for use in classroom
teaching or individualized learning
situations, is being introduced by
Heathkit/Zenith Educational
Systems.
The EE -3402 microprocessor interfacing course is designed for
students or employees with a
working knowledge of microprocessor fundamentals who
desire to gain additional
knowledge about microprocessor
interfacing techniques and more
advanced
microprocessors,
according to a company spokesman.
A 750 -page text, divided into 11
learning units, concentrates on
teaching advanced microprocessor
interfacing techniques. It also provides in-depth coverage of the
6800 family of microprocessors
and introduces the student to the
powerful
6809 and
microprocessors.
Circle (80) on Reply Card
Transistors
ISO -3
Hi-Fi, Lasers,
MicroComputers, VTR,
Spectrometers are often damaged or disrupted due to Power Pollution.
High Tech components may interact!
2.5 to 5GHz range for the many
Microprocessor
interfacing course
A microprocessor interfacing
Lightning
HAZARDOUS to
HIGH TECH EQUIPMENT!!
preamplifier, and the PR -8888
package, which includes the
PR -880 VHF/UHF/FM antenna
and GA -8800 high -gain, low-noise
preamplifier.
Both packages provide longdistance reception of all TV channels (2-83) plus FM and FM stereo,
and are designed to reduce or
eliminate TV snow, interference
and ghosting. The preamps
strengthen distant signals, improving weak channels.
equipment, UHF and microwave
installations.
Circle (77) on Reply Card
Master -Charge, Visa, American Express
TOLL FREE ORDER DESK 1-800-225-4876
(except AK, HI, MA, PR & Canada)
Digital pulser
Etronix has introduced the
model MF 512 logic pulser. The
MF 512 is designed to inject pulses
into logic nodes without cutting
SATISFACTION GUARANTEED!
Electronic Specialists, Inc.
South Main Street. Natick. MA 01760
Technical 8 Non -800: 1617-6551532
171
Circle (30) on Reply Card
MAINTAIN
Ktive,
1!
easemoo
YOUR
STATUS
as the qualified technician
you already are with the
help
Star*Tech
of
Journal Were the tech-
111111111111111111111111111111111
traces or removing ICs and to
nical monthly for the
amusements industry. If your interest in
electronics has led you into the
world of coin -operated amusement machines
and their maintenance, then we're a must for you.
Each month we save you time, money and trouble by
publishing troubleshooting tips and techniques, equipment modifications, equipment symptoms and solutions, circuit analyses, system
check-out procedures, theories of operation, and important service
news on videos, electronic pinballs and digital phonographs by every
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Its just $32 a year for 12 issues of the only technical
monitor circuit response with a
logic probe to locate logic, connective or component faults. The
pulser produces high-energy,
short -duration voltage pulses of a
logic state opposite to that of the
68000 node under stimulation. Features
include a capability to override
TTL logic nodes with narrow
pulses of automatically controlled
voltage, polarity and width.
Circle
The addition of seven new transistors to the Sylvania ECG
semiconductor replacement line
CW transceiver package
has been announced by the
Radio Company has inDentron
Markets
Distributor & Special
troduced a new 3 -band, 25W CW
Division of Philips ECG.
The new types include three transceiver and accessory package
microwave transistors. ECG63 is designed to help the novice learn
an amplifier/mixer, ECG64 an CW operation or to allow the examplifier and high speed switch, perienced ham keep in touch when
and ECG65 an amplifier for CATV he's away from a traditional power
and MATV. Application is in the supply.
publication for the amusements industry.
The fact is ... whether you're already into servicing electronic
games or are considering such a nave, Star*Tech Journal would
make your job a lot easier.
Fill out the coupon below. today. Start building your library of
technical information You can either send payment or have us bill you
(78) on Reply Card
r---rrl Str*TuO
ta:
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l
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Fill out and mail
Journal, r0 Box 1065, MonhoolvIls, NJ 00100
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D Canada -2 yrs (24 issues)-$65
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Other Countries -2 yrs (24 issues) -$98
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Circle (31) on Reply Card
September 1982
Electronic Servicing
&
Technology
69
APPLIANCE
REPAIR
The transceiver covers 80, 40
and 15 meters and will receive
SSB as well as CW. A bright LED
display gives a positive frequency
reading to aid the novice in tuning.
In addition to the transceiver,
the complete package includes a
BOOKS
Thirteen Handbooks written in easy -to-understand language by experts in the service field
with illustrations and diagrams! Acclaimed by
instructors and professionals alike! How to
diagnose and repair air conditioners, refrigerators, washers, dryers, ranges, microwave
ovens, dishwashers, vacuum cleaners, electrostatic air cleaners, RV gas appliances, hair
dryers, motors, water heaters, coffeemakers,
can openers, floor polishers, steam irons, food
mixers, lawn care appliances, electric knives,
electric and digital clocks and many others.
Also fundamentals of solid state, setting up a
shop, using test instruments and more Only
$2.65 to $4.90 ea.
code key, 3 -band dipole antenna,
head set, log book, an ARRL
license manual and a complete
radio and code course on cassette
tape.
Circle (81) on Reply Card
SEND FOR FREE PRICE LIST
Garnit, Dept. ES
P.O. Box 789
Lombard, Illinois 60148
Circle
Printed circuit board holder
This compact and rugged
printed circuit board holder and
(37) on Reply Card
solder station, from OK Machine
and Tool, is designed especially for
MOVING?
Servicing
Dual -trace oscilloscope
Hitachi Denshi Test & Measurement Division has announced the
new V-509, 50MHz, dual trace
&
Technology. Please give us
6-8 weeks notice if you're
planning on changing your
address. Just write in your
new address below and mail
this coupon, WITH YOUR
SUBSCRIPTION MAILING
LABEL, to:
51EÇTR©BiC
Subscriber Services
P. O. Box 12901
Overland Park, KS 66212
Name
Address
City
laboratory, prototype and repair
work, as well as light production
applications. The self-locking end
support slides easily to suit board
width, and board holders are
spring loaded for easy board
removal and replacement without
re-adjustment. The board may be
rotated 360 degrees for access to
both sides, and may be locked at
any angle for optimum operator
efficiency. The unit includes a
soldering-iron holder and a tip cleaning sponge.
Circle (74) on Reply Card
Powerline surge suppressors
The protection of semiconductor
State
components and circuits in com70
Electronic Servicing
&
Technology
available in models from 5 to
1300Vdc or Vac, single or three
phase with protection up to
800,000V (44,000J).
Circle (72) on Reply Card
If you're planning a move in
the near future, don't risk
missing an issue of Elec-
tronic
puters and other delicate electronic devices can be achieved by
the use of plug-in surge suppressors, from Atlantic Scientific,
capable of clamping at the proper
voltage. The fast response time
(picoseconds) makes them particularly effective as protection
against surges with sub -microsecond risetimes.
A complete line of ac, data,
signal and video suppressors are
September 1982
oscilloscope.
The 11 -pound mini -portable,
with calibrated delayed sweep, offers the field engineer a bright
12kV CRT, operation from ac/dc
or optional battery pack, plus such
features as single -shot trigger,
variable hold -off, auto focus and
full TV triggering.
The V-509 offers a 31/2 -inch rectangular mesh -type CRT with
ESR METER
checks electrolytics
metal -backed P31 phosphor and an
internal graticule. The mini scope
has a convenient channel 1 DVM
IN -CIRCUIT and is TV shop
FIELD-TESTED:
The most fantastic instrument I've
ever bought-Billings, Mt. Used it
output. This useful feature
months; it only missed onceMarinette, Wis. (Typical). Squeal
& no sync: 3 bad caps in B+ &
AGC; Many Thanks-Taos, N.M.
Please ship another; very satisfied-Glen Rock, Pa. It's fantastic
-St. Joseph, Mo. Please rush;
heard good reports-Hicksville,
N.Y. One tremendous meterAlexandria, Minn. Send your
Super meter; heard about it-N.
Olmstead, Ohio. Love that ESR
Meter-Acton, Mass. Used it intensively for 30 days; it's been
eliminates T -connector cabling
3
and time-consuming cable switching.
Circle (73) on Reply Card
Universal test lead system
Simpson Electric Company has
introduced a new universal test
lead system, designed to expand
the measuring capabilities of all
VOMs and DMMs with standard or reverse -type banana jacks.
The 23 -piece system consists of
color-coded (red and black) pairs of
instrument can be used to evaluate
bipolar and FET transistors,
diodes, SCRs, diacs, triacs and
other devices.
100%
effective-Pittsburgh, Pa.
preventive maintenance
Ideal for
:
measures electrolyte dryness &
shows up intermittent opens.
Circle (71) on Reply Card
60 -day Satisfaction Guarantee.
Dual -time base oscilloscopes
Leader Instruments Corporation
has announced two dual -trace,
dual -time base, 35MHz oscilloscopes, the LBO -524 and LBO 524L. The units are designed to
meet applications in design,
testing, and service of both analog
and digital circuits and equipment.
The comprehensive triggering
controls, including variable
48 -inch long
test leads, test lead
extenders, probe -type test prods
for general-purpose testing, and
6 -inch spring -tip hook -on probes
for no -slip connections.
holdoff, alternate triggering and
delayed -sweep triggered functions, permit stable display for
Send check or M.O. or call
(313) 435-8916 for COD
Or write for free brochure to:
Creative
e[e ciro n ic3
ESR Brochure
1417 N. Selfridge
99.00
$
Clawson, Mich. 48017
postpaid
USA
CAN.
&
Circle (32) on Reply Card
pre SEND FOR OUR NEW
e;
e: 40 PAGE CATALOG Fre
BLACK PLASTIC
CASE
MI TSU1I
UHF
VARACTOR TUNER
MODEL
PAC -TEC
SERIES
N
BLACK
PLASTIC
UES-A55
FREQ.
RANGE
470-899 MHZ
ANTENNA
INPUT
Is
i;111ffl
300 0+5
[-21('J
ENCLOSURE
ADJUSTABLE
HEIGHT FROM 1.63" TO 2.93" $25.00 EACH 10 FOR $220.00
WIDTH 6.85"; DEPTH 8".
VARACTOR DIODE
PANELS NOT INCLUDED.. BB 103 3 FOR $1.00
$5.25 PER CASE
33.8
10o FOR $30.00
Circle (70) on Reply Card
ALL ELECTROAICS CORP.
TERMS
905 S. Vermont Ave.
P 0. BOX 20406
Los Angeles, Calif. 90006
Semiconductor curve tracer
A
new
semiconductor
curve
TOLL FREE ORDER NO.
800-826-5432
tracer is available from the B&KPrecision Product Group of
Dynascan Corporation. The instrument, designated model 501A, is
designed to work in association
with an oscilloscope to display
characteristic curves for a wide
variety of discrete semiconductor
devices.
The 501A displays the unique
characteristic curves for each type
of semiconductor device. By examining these curves, the user can
determine all significant operating
characteristics of the device under
test. Test parameters measured
include gain (beta), cutoff current,
leakage current, output admittance and breakdown voltage. The
(213)380-8000
Saturday
Mon. Fri.
AK
-HI
-CA
9AM-5PM 10AM-3
M
ouanbees
L,
mded
Min order III 00
Add S 2.50
Snipping USA
Cald Res Add 6
Prompt Shipp.ng
NO COD,
® CD
Circle (33) on Reply Card
even the most complex signals.
With 500µV sensitivity, extremely
low level signals can easily be observed. A channel-one output is
available on the rear panel to drive
other less -sensitive instruments,
such as a frequency counter with
an input level as low as 50012V. The
dual -time base permits accurate
observation and time interval
measurements of complex
It's no puzzle
to order Oelrich
Service Forms
For TV -radio and two-way radio servicelegal forms for Calif., Florida and Utah.
Now at parts jobbers or write for cat. B64.
OELRICH PUBLICATIONS
4040 N. Nashville Ave., Chicago, IL 60634
Now call toll -free! 800.621.0105
Circle (34) on Reply Card
waveforms.
Use ES&T
Circle (75) on Reply Card
classified ads
min
September 1982
Electronic Servicing & Technology
71
be used in rural CATV/MATV measurement applications. Joe Waters, P.O. Box 387, Fossil, OR
97830, 1-503-763-2954.
READERS'
EXCHANGE
Needed: Heath model 5G-5257 post marker/sweep
generator. Power supply, B&K model 1640 or
Hickok model 244. Also Sams Photofact SD -13.
Caswell Davis Jr., 601 Delmar, Apt. 2, San Antonio,
TX 78210.
Needed: Power transformer, servicing schematic
and any other data for an AM radio, ERC, model
8360. These units were used in Drug Fair stores
around Maryland. Will pay all charges. Charles Harris, 1042 Ellicott Drive, Baltimore, MD 21216,
1-301-624-1914.
Needed: Time leaves and holder bracket for Panasonic clock radio, model RC7254C; please state
price. Also schematic or service information for
Zenith radio, models RE -94y (Sams TSM-154),
F474W (Sams 1501), RF-B6y (Sams TSM 159) and
RC -72y (Sams TSM0155). Will buy or pay other
costs. Able TV and Electronics, Rt. 4, Box 764,
Panama City, FL 32405.
Needed: B&K model 520B transistor tester. State
condition and price. Max Emerson, 1923 N. Texas,
Weslaco, TX 78596, 1-512-968-2913.
Needed: Used, reasonably priced, battery-powered
UHF/VHF solid-state TV signal strength meter to
Needed: Horizontal output transformer for Philco
Predicta, model 10143. Philco part number
32-8899-1, merit part number HVO-215, Triad part
number D226. Audio Associates, P.O. Box 2634,
Zanesville, OH 43701.
Needed: Audio output transformer for Sansui
stereo receiver, model 1000-A. Bob Sweet, Sweet
Electronics, 400 Superior Ave., Bogalusa, LA 70427.
Needed: Address for company named Knapp
Monark, or information on the company. W. W.
McGehee, 633 5th St. SW, Grand Prairie, TX 75050.
Needed: TAB TV service manuals in good condition. Need RCA color volume 2 (#578), GE color
volume 2 (#609), Admiral color volume 2 (#641) and
Magnavox color volume 3 (#770). Also interested in
any other TAB foreign TV manuals and CB radio
manuals. Charles E. Norris, TV-Radio Service, Box
105, Airedele Road, Ridge, MD 20680.
Opportunity knocks.
The professional world of the Electronics Service Dealer is rough.
That's why we're working so hard to make it easier for you to operate
a cost effective business. NESDA offers substantial savings on bank card and insurance rates, business contacts, technical and management
certification, and that's just the beginning.
Our members are kept informed about industry developments, and
are offered the most comprehensive managerial and technical training
programs available. Opportunity knocks. Don't let it pass you by.
For more information about the National Electronics Service Dealers
Association, write to: NESDA, 2708 W. Berry St., Ft. Worth, TX 76109.
NAME
FIRM NAME
FIRM ADDRESS
Member of State
CITY
72
Electronic Servicing
STATE
&
Technology
September 1982
ZIP
PHONE
Local
D Assn.
For sale: Sencore TC162 tube tester, used only
three months, new condition, $220. Alan R.
Salvatori, do Universal TV Service, 34 Cedar Lane,
Needed: Schematic or the address for a Dynaco
Stereo 120, 60W amplifier. Joseph Vaccarella, 15
Laidlaw Ave., Jersey City, NJ 07306.
NJ 07624.
Closter,
For sale: Bell
& Howell GR -2000 25 -inch color TV
For sale: Bird model 4351 RF wattmeter, $70;
Heathkit model HD -15 hybrid phone patch, $50;
Heathkit model HD -1250 solid-state dip meter, $75.
William Shevtchuk, I Lois Ave., Clifton, NJ 07014,
kit, fully assembled but not working. Included are
on -screen clock and channel readout and contemporary cabinet. Like new, never used. With
manuals, $250. Robert Griffith, 2 Stoney Creek
Drive, Dauphin, PA 17018, 1-717-921-8747.
1-201-471-3798.
For sale: Two B&K TV Analysts: 1075 for $50 and
For sale: Texfax volumes #8 (1966), 111 (1973), 112
(1975) and 115 (1979). Make an offer. Benjamin
Halfin TV, 603 Ivey Ave., Colonial Heights, VA
1076 for $100, plus postage. Both in working condition. Carl Ahlberg, 10 Phelps St., St. Catharines, Ontario, Canada L2P 2H4.
23834.
For sale: 300 recent ET/D schematics plus Tekfax
113, 114 and 115. Best offer. W. Perkins, 3 Allston
For sale: Sencore YF33 ringer and flyback checker
in exchange for old -type B&K 1076 analyst. Frank
M. Lurry, 7805 Grand Ave., North Bergen, NJ
Court, Cambridge, MA 02139.
07047, 1-201-861-4055.
For sale: Tekfax diagrams, December 1952 through
August 1979; 1212 diagrams for $240 plus shipping.
For sale: Sencore P29 scope with probes and
manual, guaranteed, like new, $365; Optoelectronics digital capacitance meter, guaranteed, like
new, $135; VIZ VOM, 50,000Q/V, with case,
guaranteed, like new, $40. William Bernstein, 215
Middle Neck Road, Bldg. 7, Great Neck, NY 11021.
Also radio and TV textbooks, booklets, pamphlets,
and back issues of Electronic Servicing, PF Reporter and Electronic Technician/Dealer magazines. Max Seligsohn, 1455 55th St., Brooklyn, NY
11219.
For sale: Will give away to anyone who will pick up
or pay freight on old issues of Electronic Servicing
and other servicing magazines, going back many
years. A. J. Tryba, Rt. 2, Benton, IL 62812,
1-618-627-2435.
r
LLLJLJ: The Source for Quality at Low Cost
Silicon
H.V. Tripiers
HIGH VOLTAGE
MULTIPLIERS
SYLVANIA Tripiers
ECG -500A
ECG -523
ECG -526A
212.139
212-139.01
212-139-02
212-141
212-141-01
212-141-02
212-141-03
212-141-04
ea.
51295
Bare copper
RG -59/U 75 OHM
Co -Axial Cable
Copper Braided
Shield
dielectric
(regular size)
$789
SOLDER WICK
SOL1
994
Solder Removal SW -5
;s" Wide (Thick Type1-5 feet
semiconductor.
VERY POPULAR
594 ea. $4400/100
SILICON RECTPFIER
100/5995
sL1o0
2.5Amp/1000PIV
---
GLOBAR DISC - 120 Ohms Cold
107191
RCA
99$
10 ASSORTED CIRCUIT BREAKERS
10/$799
Good Assortment
D
2
2 Way - 75 Ohm Coupler
MT -2 $109ea. $89°°/100
Foam polyethylene
lb. -.062 dia.
Full line in stock.
The best quality
75-
White or Black
1
ea.
Semiconductors
and Components
Matching30Tra0Ohnsmformer
MT -1
SOLDER (60/40 Rosin Core)
s1699
ea.
Sylvania ECG
Replacement
10CI100lot
Braided bare
copper shield
5445°/1000 ft.
51500
Sylvania
Tubes
70% + 10%
OFF
LIST
F-59 Connector
with Separate Ferrule
CD3'
conductor
REMEMBER!
1
SC1172B
80 MFD x 450 Volts... .99
100 MFD x 450
S1 99
O
CHEATER CORDS
Polarized C Clip
Price: 39C 24620
Sl 49
Standard C Clip
Price: 39C 24623
CB -10
REPLACEMENT RODS
Volts...1.09
G.E. 0M-300
Section
Section
6 Section
7 Section
4
5
LAR-4 69C
LA R-5
LAR-6
89C
99C
PANASONIC OM -500
LAR7 99C
s159
Send Purchase Order, Check or Money Order
or Call Toll
ELECTRONICS
770 Amsterdam Ave., New York, NY 10025
>
Free 800-223-0826
in NY STATE (212) 865-5580
All ORDERS SHIPPED UPS/COD F.O.B., N.Y.C.
Also ask for Free 100 Page Catalog -4
MASTER CARD
VISA
4
Circle (35) on Reply Card
September 1982
Electronic Servicing & Technology
73
Riding
Service Manuals
Lawnmower
192 pages...
big 8x11" format
The ever
popular
SMALL
ENGINES
Service
Manual
Fix your own small air cooled engines
Covers virtually all makes & models
336 pages
8x11" softbound
Chain Saw
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Small Engine/
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$9.95
$ $ $
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Manuals cover
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VCheck these other
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Large Air Cooled Engines
Snowmobile
Small Tractor Vol. 1
Small Tractor Vol. 2
Light Utility Tractor
$8.95
$8.95
$7.95
$7.95
$3.95
Get more details from our
FREE catalog...Ask for it!
Electronic Servicing
&
Technology
$8.95
Technical Publications
invites you to join
the thousands that are
doing it themselves
and saving
$
$
$
Outboard
Motor Vol.
$
$
$
Inboard/Outdrive
1
Motors below
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272 pages
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236 pages
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"
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board Engine
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TECHNICAL
PUBLICATIONS
P.O. Box 12901 Dept. ES
Overland Park, KS 66212
(913) 888-4664
VISA
master r.ha,ge
74
Lawnmower
Walking
128 pages
8x11" softbound$8.95
Indicate number, expiration date and
type of card
No COD outside US
POSTAGE PAID when payment accompanies order
September 1982
www.americanradiohistory.com
you
ASK =D
FOR IT...
YOUGOT'T.
GIGOTRODIC
September 1982
Electronic Servicing
&
Technology
75
For Sale: B&K 415 Swp/Mkr Gen. W/Cables $200; B&K
466 CRT Tester W/Adapters $40; Sencore Color Gen
CG169 $125; Sencore Cricket Transistor Tester $50;
Sylvania TV Test Jig CK1500 W/Cables $175;
XL -100 TV Test Modules (10) $100. Don Renwick, 6318
Rygate Dr., Reynoldsburg, OH 43068. 614-8666722.
9-82-1t
THE
MARKETPLACE
DESPERATE-MUST SELL: New, Sencore SC60: Dual
Trace Oscilloscope still in box with accessories,
904-781-3772. Jim Smith 8616 Graybar Dr., Jax, Fla
32221
Advertising rates in the Classified Section are 50
cents per word, each insertion, and must be accompanied by payment to insure publication.
E.T. MAG 54.82/TEXFAX. Sams Old Tubes Equipment,
Each initial or abbreviation counts a full word.
TV
Minimum classified charge $10.00.
toms/remedies by circuit area; tough ones over the
years. Save time and money. Send $12.50 to CHAN TV,
8151 Grandview Rd., Chanhassen, Mn. 55317. 5-82-tfn
For ads on which replies are sent to us for forwarding
(blind ads), there Is an additional charge of $3.00 per
Insertion to cover department number, processing of
replies, and mailing costs.
Classified columns are not open to advertising of any
products regularly produced by manufacturers unless
used and no longer owned by the manufacturer or
distributor.
For Sale
I
9-82-1t
it
Retiring, Roya 1-802-433-5487.
TROUBLE ANALYSIS
9.82.1t
TIPS. Over 300 symp-
SPECIALS, RG-591U COAX CABLE. 100% shielded$49/M: Fó9 connectors with separate ring $11.95/100.
15-300 OHM Matching transformers $39/100. CZ Labs,
55 Railroad Ave., Gavnerville, NY 10923 (914) 947.1554,
8-82-tf n
SATELLITE EARTH STATION-Complete system
$2,985 retail. Aluminum dish, polar mount, 120° K
LNA, modulator, rotor, 24 -channel receiver, 150' of
cable. Dealer's price list and free brochures. Call
618-397-5755 or write D.K. Electronics, 5 Frederick
Street, Belleville, IL62223.
8-82-2t
Wanted
THE GREAT ELECTRONIC
BOOK!
THINGS & IDEAS
HUNDREDS OF
IUNUSUAL PARTS. GADGETS & IDEA ITEMS. UNAVAILABLE IN
STORES OR CATALOGS ANYWHERE! Barger pr,us on everything!
New ,tams ,n every inc.' Rush postcard for your copy,
ELECTRONICS
Dept. 311
Plattsburgh, N.V. 12901.
Circle (39) on Reply Card
AUTOMOBILE RADIO and tape replacement parts:
Delco, Chrysler, Philco-Ford, Motorola, Panasonic and
many others. Large inventory. Laren Electronics. Inc..
3768 Boston Road, Bronx, NY 10469, (212) 881-9600,
out of New York State (800) 223-8314.
5-79-tf
ELECTRONIC SURPLUS: CLOSEOUTS, LIQUIDATIONS! Parts, equipment stereo, industrial, educational. Amazing values! Fascinating items unavailable
in stores or catalogs anywhere. Unusual FREE catalog
ETCO-011, Box 762, Plattsburgh, N.Y. 12901.
6.78-lf
WANTED FOR CASH: 53, 7F7, 7N7, 6AF6, 6HU8,
304TL, 4CX1000A, 4-1000A, all transmitting, special
purpose tubes of Eimac/Varian. DCO, Inc., 10 Schuyler
Avenue, North Arlington, New Jersey 07032, Toll Free
(800) 526-1270.
5-82-tf n
WANTED: $1.00 for Sams Photof acts number 1300 and
later and MHF series. Write Mr. Russell; 112 North
Turner; Fairbanks, AK 99701.
9-82-2t
Business Opportunity
TV TECHNICIANI Increase your Income up to $60,000
yearly. Rent -lease -sell TVs new -used, even from comfort of your home. Basic Preliminaries $10.00. Perrys
TV Systems, Hwy 181, Box 142, Route #1, Bremen, KY
42325.
12-81-tf
MECHANICALLY INCLINED INDIVIDUALS: Assemble
electronic devices in your home. Knowledge or experience not necessary. Get started in spare time.
Turn your spare or full time into cash. NO investment.
Write for free details. ELECTRONICS DEVELOPMENT
LAB, Box 1560ES, Pinellas Park, FL 33565.
5-82-tfn
LEARN TO REPAIR ATARI'S: Did you know that more
than 2 million Atari Home Video games have been
sold and that most of them are now out of warranty?
Why not learn how to repair these games and expand
your shop's earning potential. At Electronic Institute
of Brooklyn we have put together a Video Taped
course for the T.V. technician which will take the
mystery out of repairing Atari games. These repairs
can be done using equipment you probably already
own. Included in the course are the video tape,
schematics for the two different boards, technical
literature for the IC's, and a list of sources for replacement parts. We have condensed months of research
into a neat package that will enable you to start repairing Atari's right now! Our course is available on VHS
or Beta system tapes. For more Information or to order
CALL TOLL FREE 1.800-221-0834 or (212) 377-0369.
Electronic Institute of Brooklyn, 4823 Ave. N,
Brooklyn, N.Y. 11234.
7-82-4t
HIGH PROFITS-LOW INVESTMENT: with our CRT
rebuilding equipment. Complete training and
technical assistance. Guaranteed result. Atoll Television, 6425 Irving Park, Chicago, Illinois 60634; PH. 312545.6667
8.823t
DEALERS EARN EXTRA PROFIT selling cable TV converters, Video accessories and other great items in
our brand new dealer catalog. Request a FREE copy
on your letterhead. ETCO, Wholesale Division, Dept.
535, Box 840, Champlain, N.Y. 12919.
9-82-12t
PRINTED CIRCUIT BOARDS manufactured from your
sketch or artwork. Reasonable rates, quick delivery.
Satisfaction guaranteed. Contact Fred C. Monteith,
c/o Monitor Circuits, 804 Schmitt Road. Rossville,
Georgia 30741.
9-82-1t
ATTENTION MANUFACTURERS: Printed circuit board
work wanted requiring assembly or hand finishing.
Contact Fred Monteith, c/o Monitor Circuits, 804
Schmitt Road. Roseville, Georgia 30741.
9-82-1t
Help Wanted
Technicians wanted. $15K to $22K per
year. Benefits include employee stock purchase plan,
largest
In the
Retail Service Center In Northwest Kansas. Friendly community, good schools, short drive to
the Rockies. Equal Opportunity Employer. Miller's
Electronics Inc., Goodland, KS 67735.913-899-2386.
TV and 2 -way
10.81
SCRAMBLED TELEVISION, encoding/decoding. New
book. Theory/circuits. $9.95 plus $1 shipping.
Workshop, Box 393ES, Dept. E, Bethpage, N.Y. 11714.
7.80-t f
PRINTED CIRCUIT boards from your sketch or artwork. Affordable prices. Also fun kit projects. Free
details. DANOCINTHS INC. Dept. ES, Box 261,
Westland, MI 48185.
5 -81
-tin
ADVERTISERS'
INDEX
SONY -PANASONIC -RCA -ZENITH -EXACT REPLACEMENT PARTS-LARGE INVENTORIES -SEND PART OR
MODEL NUMBERS-WILL UPS OR COD -GREEN TELE
RADIO DISTRIBUTORS, 172 SUNRISE HIGHWAY,
ROCKVILLE CENTRE, N.Y. 11570.
5-82-tf
26
20
24
31
27
TRANSLETERONIC INC., 1365 -39th Street, Brooklyn,
N.Y. 11218E, 800-221-5802, 212-633-2800.
5-82-tf
36
connector on each
end, packaged -3'-898; 6'-$1.05; 8'-$1.10; 12'-$1.20;
20'41.50; 25'-$1.60; 50'-$3.25; 75'-$3.95; 100'-$5.95. Call
or write for our free catalog. CZ Labs, 55 Railroad
Avenue, Garnerville, NY 10923.914.947.1554.
5.82-3t
MOST POPULAR CRITICAL SAFETY COMPONENTS:
Magnavox 250663-11 and 250663-17; G.E. EP25x60 and
EP25x75, $3.49 each, 10 for $32.00. 430Mfd @ 200 WV
(Mallory) axial electrolytics $2.45 each, 10 for $22.00.
NORFOLK ELECTRONICS, P.O. Box 91, 55 Railroad
Avenue, Garnersville, N.Y. 10923.
5-82-2!
76
25
TUBES-Receiving, Industrial and Semi -conductors,
factory boxed. Free price list. Low, low prices.
RG -59/U COAX ASSEMBLIES, F-59
Electronic Servicing & Technology
34
35
22
Leader Instruments Corp
Leasametric
NATESA
41
NESDA
72
NRI Schools
37
New Tone Electronics
Oelrich Publications
Omnitron Electronics
Optima Electronics
31
Pace
33
REPLACEMENT COLOR YOKES-DEALERS ONLY.
Zenith 95-2501-2532-2887 etc. $22.95. Magnavox
36180-1 etc. $24.95. Sylvania $24.95. American -made
fuses in bulk. Request circular on your letterhead.
David Sims Enterprises, Inc., 665 East Jericho Tpke.,
Huntington Sta., NY 11746. 800-645-5030, NY State
(516) 549-3925-1592.
5 -82 -tin
38
30
37
15
18
6
29
16
4
All Electronics
Atkinson Dynamics
Automated Production Equipment Corp.
B&K Precision
Chips Technology
Cleveland Institute of Electronics
Creative Electronics
71
DATA
43
Digitron Electronics Corp
61
13
ETA
68
ETCO
76
37
69
70
10,11
2,3
Electronic Parts Supply Co
Electronic Specialists, Inc
Gamit Enterprises
General Electric Co.
Tube Production Div.
Global Specialites Corp.
H&R Communications, Inc
Heathkit
Hitachi
Hykon Manufacturing Co
Inter-Tec
Jensen Tools, Inc.
Keithley Instruments Div.
September 1982
60
60
28
23
51
59
39
39
68
71
43,73
58
41,78
Panasonic
Philips ECG
Phipps & Bird Inc
Primefax
PTS Corp.
Distributor & Special
Products
RCA Technical Publications Div
RNJ Electronics
Howard W. Sams & Co.
Sencore, Inc
Sencore, Inc.
Sentry
Simpson Electric Co
Simple Simon Electronics Kits,
Inc.
Soltec
Sperry Tech, Inc.
Sprague Products Co
Spectrum Electronics
Star Tech Journals
11
15
61
37,59
IFC
RCA
71
21
9
14
33
36
41
17
45
39
5
9
31
67
35
78
36
19
3
-tin
7
.
Soltec
Thordarson-Meissner
Tektronix
Zenith Radio Corp.
12-13,24-25
63
43
27
18-21
BC
56
17
29
36
45
7
53
69
65
49
23
IBC
st rich
Strike
in the lastest growing segment
of the TV business
with a line of VCR and Video Disc Player
accessories as strong as its name.
Zeniti brings
you an assortment of
the fastest-moving
ters, attenuators,
switches, "F", mini, and
other types of plugs
and jacks in virtually
any combination, plus
cables in a variety
of lengths each with
gold -electroplated
connectors. All with
the built-in acceptance
of TV's leading name
for qual ty home entertainment products.
Call your Zenith distributor now for his strike it -rich VCR and Video
Disc Player Accessory
terminators,
Program?
Now,
and Video Disc
Player accessories,
each individually packaged and labeled to
sell on sight from the
54" x 36" floor display
as shown. Prominently
displayed are such
accessories as dust
covers, video tape ID
kits, cassette storage
modules, signal splitVCR
A -B
N
71111.1181:111111.....""---goes in before the name goes
Thelity
on'
Zenith Radio Corporation/Service, Parts & Accessories Division/11000 Seymour Avenue/ Franklin Park, Illinois 60131
Now Cut Your
TV-VCR ServiceTime
Absolutely In Half
CHANNEL
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A.
Cut your time in half. You
WILL cut your service time in
half with a Sencore VA48 Video
Analyzer. Over 1500 VA48 owners
nationwide report an average
time savings of 54%! These techs
quickly and easily learned the
VA48's Signal Substitution Method
of troubleshooting. It's the key
to DOUBLING your service output.
Signal Substitution is the
key. Our double -patented Signal
Substitution Method lets you inject
known good signals from the VA48
into any stage of a TV or VCR.
If you get a good picture, you know
everything is working from that
point forward. You back up stage by
stage until the defect appears on
the screen. You then know you are
injecting into the defective stage.
It's just that simple, and only
the VA48 provides ALL signals
necessary to inject from antenna to
CRT It literally cuts your service
time in HALF
Join the thousands
... 22,000
VA48 users know this video
analyzer is the new standard of
the industry. So do manufacturers
who are specifying the VA48's
patented Bar Sweep patterns on
their schematics. Look in Sams
Photofact schematics. The VA48
Bar Sweep is there, too.
Money back guarantee. We're
so sure you'll cut your TV-VCR
service time in half, we offer your
money back in 30 days if you're not
absolutely satisfied. PLUS, when
you order now, you'll
receive a FREE copy
of Bob Goodman's
new $18.95 best
seller, "Practical
TV Trouble-
shooting
With A
Video Analyzer.
yours to keep FREE regar. -ss.
Call toll -free. Call now to order
or to talk about the VA48 features
with a qualified Sencore enginerring
representative.
3200 Sencore Drive, Sioux Fats, SD 57107 605/339-0100 TWX: 910-660-0300
For information Circle (2) on Reply Card
For Demonstration Circle (3) on Reply Card
For More Information or To Order
Phone Toll-Free
1
800-843-3338
In Alaska. Hawaii. and Canada. phone collect. 605 339-0100
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