Eiectrom Servicing - American Radio History

Eiectrom Servicing - American Radio History
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July, 1976
75 cents
Eiectrom Servicing
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Satellite UpdâlÔ
"How's That, Again?"
HOWARD W. SAMS PUBLICATION
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reliability and the
From the beginning,
our goal has been to
provide the best tuner
standards of excellence we apply to every
¡ob. Thousands of PTS
customers must agree or
we wouldn't be the world's
largest tuner service company.
When you are comparing tuner service
companies, price alone doesn't tell the story.
service never the
cheapest. You get what
you pay for in business
and tuner service is no exception.
The extra dollar you might pay at PTS
is peanuts when you consider the added
SAME DAY SERVICE
ORIGINAL PARTS
WE REPAIR THEM ALL
.
.
.
or UHF.
.
.
ONE YEAR
UARANTEE
COLOR, BLACK & WHITE, TUBE,
TRANSISTOR OR VARACTOR
VHF
LT El
E'
.$10.95
.
.
.
ANY MAKE OR MODEL.
UV -Comb.
(MAJOR PARTS AND SHIPPING EXTRA
.
.
.$17.95
DEALER NET)
PTS ELECTRONICS, INC.
111
PRECISION TUNER SERVICE
General Headquarters: P.O. Box 272, Bloomington, IN 47401
THE COMPLETE LIST OF ALL PTS SERVICE CENTERS APPEARS ON THE NEXT PAGE.
For More
Details Circle (1) on Reply Card
Riley really rallied
to our"rally 'round the tab:
Our 1976 "rally 'round the tab" award program is under way, and a lot of dealers and
technicians are already collecting awards ranging from coffeemakers to camping gear.
You can start collecting, too. All you have to
do is tear off the tab-the end flap of Sylvania
receiving tube boxes with the Waltham, Third
Ave. or Broadway address on it.
And save color picture -tube serial labels, too.
They're worth the equivalent of 20 receiving
tube tabs. (You'll find the label on the upper
left-hand corner of every carton.)
Then just pick the awards you want from
over 300 items in the official catalog and drop
your order in the mail. Keep in mind, the program ends at midnight November 30th, 1976.
You can get your catalog, order forms and
mailing kit from your local Sylvania Distributor
or from Sylvania Award Headquarters, P.O.
Box4000, Fenton, Missouri 63026.
Start your tab collection today. It's our way
of helping you to live the life of Riley.
CaD SYLVANIA
July, 1976
3
0
scanner
news of the industry
Quasar Electronics has started shipments of a new 12 -inch diagonal solid-state
portable color television receiver. The unit weighs about 28 pounds and consumes
less energy than a 75 -watt electric light bulb. The receiver has an in -line
matrix -striped color picture tube with an additional pre -focus lens to sharpen the
focus. A "picture control" allows the customer to regulate or maintain the balance
of contrast, brightness and color intensity. Suggested list price is $329.95.
Magnavox has designed a new tuning system for some of its TV receivers. The new
system uses five IC chips and a programmable memory. A quartz crystal is used to
provide an on -screen time display on demand or when the channel is changed.
Channel selection is done with a 12 -button telephone -type keyboard. There is a
two -digit, one -half-inch -high LED channel display. Electronic News states the new
system is going into nine 25 -inch models and two 19 -inch models made by
Magnavox, while the older electronic Star tuning system will continue to be used
on 12 models.
The Finney Company is to open factory number three in Clinton, Kentucky.
VIZ Manufacturing announced a new product introduction program at the
NEWCOM '76 Show in New Orleans. Russel Hurst, president of VIZ, said the
program would bring out 12 new products in 12 months. The products will include
two new digita' multimeters; an FET VOM; signal, pulse, and function generators;
an oscilloscope; two wattmeters; a low -price high -quality VOM; and a power
supply. VIZ acquired the RCA test instruments business last December.
Both GTE Sylvania and RCA have indicated that they are interested in the
Rauland picture tube manufactured for Zenith, but not the glass design. Alfred
Viebranz, Senior Vice President of the Electronic Components Group of GTE
Sylvania, stated that "The prime new feature of the Rauland tube, of interest to us
and our customers, is the tri -potential gun. This premium gun appears to have the
potential of providing picture performance equivalent to the current Delta -gun
tube while allowing most of the attendant in -line chassis savings to the set
producers. We will be competitive in this area."
William W. George, president of Litton Microwave Cooking Products, recently
predicted an increase of 40% in industry sales of home microwave ovens to 1.4
million units this year. Litton division's own consumer sales for the first three
months are up more than 150% over 1975's first quarter. In 1975, more than 1
million units were sold by the industry.
RCA Distributor and Special Products Division has announced a new program
under which dealers and service technicians will receive credit for returning
defective, out -of -warranty modules against the purchase of a replacement module.
The amount of credit depends on the type of dud returned, with a range from $3
to $10 per module. Credit will not be given for damaged modules. The program is
especially important with respect to older chassis designs where some modules are
currently being phased out of production.
(Continued on page 6)
4
ELECTRONIC SERVICING
NSERVIC
,Us,
SllßSihlLIEß
.
RPO
.
STILL ONLY
ONE YEAR
GUARANTEE
95
ti
..
.S.A.
ONLY
1St
ONLY
Q'
t. ¡ in
_
MAJOR PARTS
AND SHIPPING
CHARGED AT COST
WITH CABLES
I
F
TE UA
PROVIDES YOU WITH A COMPLETE SERVICE
FOR ALL YOUR TELEVISION TUNER REQUIREMENTS.
RES
A UHF Tuner
with 70 channels which are
detented and indicated just like VHF channels.
A VHF Hi Gain Solid State Tuner.
AC Powered
90 Day Warranty
VHF OR UHF ANY TYPE
UHF/VHF COMBINATION
EMIEMZI
Fast, efficient service at our conveniently located
Service Centers.
tuners are ultrasonically cleaned, repaired,
realigned, and air tested.
All
You may place your order through
any of the Centers listed below.
REPLACE
UNIVERSAL REPLACEMENT TUNER $12.95 (U.S.A. only)
price buys you a complete new tuner built specifically by Sarkes Tarzian Inc. for this purpose.
All shafts have a maximum length of 101/2" which
can be cut to 11/2".
Specify heater type parallel and series 450 mA.
or 600 mA.
This
NEWS FLASH!
NOW AVAILABLE-TUNER SERVICE
PARTS CATALOG OF ALL SARKES
TARZIAN VHF AND UHF TUNERS, INCLUDING EXPLODED VIEW DRAWINGS.
OVER 200 PAGES. ORDER YOUR COPY
TODAY. SEND $2.50 WITH ORDER TO
BLOOMINGTON HEAD OFFICE.
TSC
CUSTOMIZE
Customized tuners are available at a cost of only
$15.95. With trade-in $13.95.
(U.S.A. only)
Send in your original tuner for comparison purposes
to any of the Centers listed below.
BLOOMINGTON, INDIANA 47401
TUCSON, ARIZONA 85713
NORTH HOLLYWOOD, Cgl.F. 91601
URLIN ,,
ALIF. 9409b
DES +
ALI .
FLORIDA
GEORGIA
A
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N. CAROLINA
OHIO
OREGON
PENNSYLVANIA
WATCH US
GROW
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LOUT- ANA 71
.ORE, MAR LANDSPRINt
LD, MÁ 8. 01108.
ST. LO '
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163132.
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LAS VEGA
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1WLJ RSEY 086
TY, NE
7307
i"':ß.1T NEW YO
GREEN
. N.C. 27405
CINCINK . , 0' 0 45216
CLEVELAN
;OHIO 44109
PORTLAND, .REGON 97210
PITTSBURGH, PA. 15209
MEMPHIS, TENNESSEE 38111
DALLAS. TEXAS 75218
NORFOLK, VIRGINIA 23513
ST. LAURENT, QUEBEC H4N-2L7
T.
1505
Tel.
..646 Ev
....405 Ea
1 ' 7..5110 r,
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CALGARY, ALBERTA T2H-1Y3
7450 Vine S
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(6) on Reply Card
2
6400
4444
5-02302-3493
78-4217
. 51-3027
1
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Cc58-1186
x,_788-8206
4-429-0633
609-393-0999
201-792-3730
I. 716-647-9180
919-273-6276
513-821-5080
16-741-2314
1.
Street
._
.
_
-
3158 on Avenue
11540 Garland Road
3295 Santos Street
305 Decarie Boulevard
P 0 Box 5823, Stn. "A"
,
10141.
,
.\
,'3-222-9059
T-'
2-821-4004
Tel. 901-458-2355
Tel. 214-327-8413
Tel. 804-855-2518
Tel. 514-748-8803
Tel.
IF YOU WANT TO BRANCH OUT INTO THE TV TUNER REPAIR BUSINESS,
WRITE TO THE BLOOMINGTON HEADQUARTERS ABOUT A FRANCHISE.
For More Details Circle
914
702-384-4235X
a
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25 P
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1
2 N.
.25th Ave., P.O. Box
51 ra t Avenue
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.5505 Re_1g( stows
I c k'ins
...9'77 Page Avenue..
1
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37 Pull an A
2914 E. Marke
.
., c.
.3025 Highland Ave
...1139
...547-49 Iginne
812-334-0411
602-791-9243
213-769- 720
41528
209-5
S.W..sl. 404x*
-
st Brown tr
.112 Wes St. Clai Str:.
.5005 Dou
MSE.
'319. ..
OR
.
NEW YORK
TENNESSEE
TEXAS
VIRGINIA
CANADA
6i'ß
P NOIS
IS, INDIA
l
IOWA
KENTUCKY
LOUISIANA
MARYLAND
MASSACHUSETTS
MISSOURI
NEVADA
NEW JERSEY
Tel.
Tel.
Tel.
Tel.
Tel.
33315.... ....104 S. .23rd
E
IDA
ORIDA
TA, GA. 30 10
IGN, ILLI r1s aga.,
L
INDIANA
537 South Walnut Street
1528 S. 6th Ave.
10654 Magnolia Boulevard
1324 Marsten Road
123 Phoenix Aven
a
LORIDA
ILLINOIS.. t
9.95
$15.00
$
MAJOR PARTS AND SHIPPING
CHARGED AT COST
Demonstrate the
to
your customers and show improved
reception with their TV sets.
HEADQUARTERS
ARIZONA
CALIFORNIA
(U.S.A. ONLY)
(U S.A. ONLY)
403-243-0971
M
flCiffiller
news o the .ndustry
EContinued from page 4)
Projection television sales appear to be growing. An improving business climate
and a scattering of lower prices seem to be responsible for the upswing. It is
estimated that sales may climb to 100,000 annually within the next three years.
new packaging service is being offered without charge by PTS Electronics.
Repaired tuners, rebuilt modules, and tuner test -instrument kits are now packaged
in special plastic skin packs to eliminate shipping damage and dirt. The package
provides an airtight seal that prevents the contents from moving, as well as
providing a cushion during shipment.
A
Jer*old Electronics has scheduled MATV Schools to be held during the second half
of 1976. The schools cover basic and advanced Master Antenna TV systems, in-
cluding system design, headends, distribution systems, calculating losses,
eliminating interference, and installation techniques. Anyone interested in attending these schools should contact the Jerrold Distributor Sales Division, 200 Witmer
Road, Horsham. Pa. 19044.
RCA's new 1977 line of color television receivers emphasizes the "Color-Trak"
system, and is aimed directly at the second -set market, which now accounts for
60`0 of the total sales. The "ColorTrak" system has been expanded to include
almost three -fourths of the basic new line. A late -summer national promotion,
"Trades Fantastic", will be launched by RCA to increase console receiver sales
among previous color set owners, who will receive an advertised trade-in allowance
of up to $100 on a used color TV set with the purchase of a ColorTrak console.
Laser tracking equipment that helps evaluate the performance of new parachutes
and ejection systems has been developed by GTE Sylvania. The unit sends a laser
pulse to a parachute -mounted reflector which returns it to a receiver. By measuring the transit time and position of the return pulse, the receiver determines the
range from the retroreflector. Added to a photographic system, the equipment will
provide automatic target tracking.
6
ELECTRONIC SERVICING
PHENOMENAL BREAKTHROUGH
IN UHF RECEPTION!
Don't say you can't get good UHF reception
until you've tried this new combination by Winegard
New Super Lo -Noise
Preamp With New
Antenna Makes Poor
Pictures Good and Fair
Pictures Excellent
Good reception of UHF stations is more important than ever. Programming has greatly improved in
recent years on the U's
and many offer exclusive sports coverage
viewers so eagerly want. If you sell sets
or install antennas in UHF areas, you know
what we're talking about.
Winegard AC -4990 Preamplifier Combined With
CH -9095 Antenna Delivers Amazing UHF Reception.
The Problem
You also know what we're talking about
when we say that reception of UHF sta-
tions in most areas is rarely as good as
you get on the VHF stations. This is a
major, universal problem.
Why the problem? For one thing, many
UHF stations are not on full authorized
power. And, transmission line losses at
UHF frequencies present difficulties. But
the biggest culprit of all is the high noise
figure of the TV set tuners at UHF frequencies.
Generally speaking, you have to deliver
3 times as much clean UHF signal to the
set as you do VHF signal
in order to
get comparable reception.
The quantity and quality of UHF signal
you feed the set is greatly determined by
the antenna and preamplifier you use.
-
SPECIFICATIONS
AC -4990
GAIN
UHF
BANDPASS (MHZ)
VHF -FM
UHF
17.5db
54 to 216
470 to 890
A few months ago Winegard Company in-
troduced a new line of Chromstar UHF
antennas featuring a new Tri -linear director system. This configuration offers the
highest gain we've ever seen on a UHF
antenna and the field reports we've been
getting from professional installers have
been most enthusiastic.
Now Winegard Company is introducing
another ...and even bigger breakthrough.
This is a super to -noise UHF preamplifier,
Model AC -499W' It has a 6db signal-tonoise improvement over the best UHF pre amps previously available.
Combine the AC -4990 with a Winegard
CH -9095 Chromstar UHF antenna and you
get a 9db improvement or 3 times cleaner
signal.
This means you can give good UHF pictures to customers who can barely get
UHF now. It means you can deliver "excellent" reception to those who now receive just "fair" pictures.
UHF
July, 1976
actual practice, good reception of all
UHF stations is now extended up to 30
additional miles... in many cases nearly
doubling the effective reception range.
New Sales Potential
Potential sales of CH -9095's and AC 4990's are greatly increased. This combo
can be sold in areas where UHF reception hasn't been good enough to bother
with and, as a replacement for customers
who are only getting "fair" reception now.
Incidentally, the AC -4990 preamp has a
VHF bypass so it can also be used with
any Winegard V -U Chromstar antenna with
excellent results.
Antenna dealers in UHF areas are advised to try this new Winegard antennapreamp combination as soon as possible.
Seeing is believing ...and the new profit
opportunities are tremendous.
NOTE: Due to demand, the AC -4990
preamp will be in short supply for a few
months. An order should be placed now
with your Winegard distributor.
WINEGARD
COMPANY
.882
MAX. TOTAL INPUT
(Volts)
NOISE FIGURE
UHF
In
*Pat. Pending.
MAX. TOTAL OUTPUT
(Volts)
UHF
The Solution
.126
3000 Kirkwood
Burlington, Iowa 52601
2.2db
For More Details Circle
(7) on Reply Card
7
Symptoms and cures
compiled from field reports
of recurring troubles
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Chassis-RCA CTC49X
Chassis-RCA CTC63
PHOTOFACT-1362-2
PHOTOFACT-1187-2
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TO CR402
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Symptom-Intermittent vertical jitter
Cure-Check R105, R109, and R110. Replace if out of
Symptom-Piecrusting that varied with brightness
Cure-Check R24, and replace it if open
tolerance, and readjust R107
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Chassis-Truetone MIC-4212-27
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Symptom-Herringbone pattern in red picture
Cure-Check R191, and replace if it is reduced
1
in
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Symptom-No color on left half of screen
Cure-Check C34, and replace it if open
value
.1110 MM.
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AGC
Symptom-Colored snow off channel, but no color
Symptom-Video blanks out, requiring adjustment of
on station
AGC
Cure-Check C630, and replace it if shorted
Cure-Check C39, C41, and the grid of V2A for
leakage
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ELECTRONIC SERVICING
troublesìootimió ó
Send in your helpful
rips-we pay'
No video,
and excessive brightness
General Electric 25MB Chassis
(Photofact 1400-3)
The symptoms were a very -bright
raster without video, and that the
brightness could not be reduced
enough by either the brightness or
the screen controls. None of the
CRT grids should have any kind of
AC signal, but each should have
the same DC voltage, determined
by adjustment of the CRT -Bias
control. However, the grid voltages
were not suspected because no
defect there could remove the video.
Excessive screen -grid voltages
would cause too much brightness,
but the brightness control should
work, and the video should be
present.
Neither screen -grid or control grid troubles could cause the symptoms, so those two areas were
cleared of suspicion for the moment.
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The brightness control changes a
DC voltage in the video amplifiers,
thus the cathodes of the picture
tube should have video/chroma
signals, plus DC voltages that vary
with the brightness control. At the
cathodes, I measured almost zero
volts DC, instead of the normal 120
to 180 volts. This proved the defect
was in the video. But where in the
video was it?
I removed the video module and
measured the DC voltage at pin 13
of the module socket, finding zero
again.
Both the boost (screen -grid
supply) and the +201 -volt boost
supply (for video outputs) come
from rectification of the sweep
waveform at the flyback, and the
components are located on terminals above the flyback. Looking
there, I quickly spotted a burned
resistor, R1602, which feeds voltage
to the screens. But that couldn't be
the main defect, because the CRT
July, 1976
had screen voltage.
Next, an ohmmeter test proved
that C1624 was shorted, and the
100 -ohm resistor (R1622) in series
with the diode checked open. But
the two diodes (Y1601 and Y1621)
were okay. Replacement of the
capacitor, the resistor, and the
burned resistor in the boost circuit
restored normal operation.
Roger D. Redden
Beaver, West Virginia
COMPLETE SERVICE ON
ALL MAKES OF TV TUNERS
Maximum Time In Shop 24 Hrs.
(WE SHIP C.O.D.)
(Warranty: One Full Year)
Picture bending
Zenith 14L36 chassis
(Photofact 707-4)
The customer complained of
bending in the picture on the
screen of this old portable TV.
The bends were steady, and did
not roll as is usual with hum from
a tube leakage, or a defective filter
capacitor. Pictures from broadcasting stations are not ideal for
troubleshooting bends, so I changed
to the vertical lines from a color bar generator. Now, the bends
could be changed, by use of the
horizontal -hold control, from a distorted "S" curve to a reversed "C"
shape.
Concluding that the first circuit
to check was the horizontal AFC, I
replaced the 6KD8 tube of that
circuit; however, there was no
change. After measuring +3.1 volts
DC of AFC control voltage at the
junction of R70 and R71, I clamped
this point with the same DC voltage
from my bias supply. Although the
picture drifted sideways, the bends
clearly still were present. From the
test, I concluded the defect was not
in the dual -diode phase -detector
circuit. Next, I checked waveforms
and DC voltages at the 6KD8 tube.
Nothing abnormal was found.
After some thought and searching the schematic, I noticed a
capacitor, C42, which was connected between the horizontal -AFC
circuit and the cathode of the
vertical -output tube. Could the
bends be caused by a defect in the
capacitor, or in the vertical -output
circuit?
Although I thought those possibilities to be remote, I did replace
the vertical -output tube. To my
surprise, the trouble of the bends
was corrected.
Al Ferrara
Upper Darby, Pennsylvania
YOU
PAY
SHIPPING
$9.95
Black &
White
or Color
VHF or
UHF
UV Combo's $16.50
Price includes all labor and parts except Tubes, Diodes & Transistors. If
combo tuner needs only one unit repaired, disassemble and ship only
defective unit. Otherwise there will
be a charge for a combo tuner.
When sending tuners for repair, remove mounting brackets, knobs, indicator dials, remote fine tuning arrangements and remote control drive
units.
WE UNCONDITIONALLY
GUARANTEE All Tuners
FOR
ONE FULL YEAR
All tuners are serviced by
EXPERTLY
TRAINED TECHNICIANS with years
of experience in this specialized
field. All tuners are ALIGNED TO
MANUFACTURER'S SPECIFICATION on crystal controlled equipment and air checked on monitor
before shipping to assure that tuner
is operating properly.
GEM
CITY
TUNER SERVICE
Box 6G Dabel Station
1621 Mardon Drive
Dayton, Ohio 45420
9
oxcbanoo
Needed: Deflection board for Delmonico-Nivico,
Model TR -27; quote price.
C. R. Ashburn
1820 Vista Lane
Timonium, Maryland 21093
Needed: Power transformer
for
a Hickok scope,
Model #670.
Tagliarini
8816 N. Himes Avenue
Tampa, Florida 33614
S.
Needed: Schematic and service data for Squires and
Sanders Model #SS -310 CCTV camera. Will buy, or
copy and return.
Allen Rees
P.O. Box 1271
Norman, Oklahoma 73069
Needed: Schematic and other data on Knight
oscilloscope, KG -2100 D.C. Will buy, or copy and
return.
Lawson TV Service
8515 S. Throop St.
Chicago, Illinois 60621
SERVICE/INDUSTRIAL
CATA LOG
11111
Needed: Schematic and service data for Monarch
stereo amplifier, Model SA -40A. Will buy, or copy
Over 5000
Products.
and return.
* GC * WALSCO * TELCO » CALECTRO
* ELECTROCRAFT * AUDIOTEX CB
s7"
SEE YOUR DISTRIBUTOR
TODAY FOR YOUR
FREE COPY
!
GC
10
GC ELECTRONICS
HYDRO METALS. INC.
ROCKFORD,OF ILLINOIS U.S.A.61101
DIVISION
Needed: Operating manuals for Superior Instrument
Model #76 bridge, and an RMS bar generator, Model
#BAH 1.
Robert Crocker
936 West End Avenue
New York, New York 10025
8 Major Product Lines.
tami336 Pages With
IIIII Alpha & Numerical
Indices.
ELECTRONICS
Needed: A power transformer for a Jackson Electrical
Instruments voltohmmeter, Model #590.
Royal Furniture Co.
186 Pembroke St., West
Pembroke, Ontario K8A 5M8
Needed: Schematic and/or power transformer for a
Fairbanks -Morse radio, chassis 91. Please write
before sending transformer.
Randy Ives
Route 2
Satanta, Kansas 67870
COMPREHENSIVE
mir
Needed: Manuals and schematics for Precise scope,
Model 300, and Jackson condenser tester, Model 112.
Will buy, or copy and return.
Joe L. Dennis
15838 Vanowen St.
Van Nuys, California 91406
Needed: Unused number 1626 receiving tube.
Albert Pecaites
4048 West 161st St.
Cleveland, Ohio 44135
A M ERICA'S MOST
11111
Wanted: Pre -1926 battery radios, crystal sets, tubes,
radio magazines and pre-war televisions such as RCA
TRK-5, 9 or 12.
Donald O. Patterson
1220 Meigs Street
Augusta, Georgia 30904
,
likr
Precision Radio and TV Service
7512 Marie St.
Columbia, South Carolina 29209
Needed: Schematic and manual for Series 954
Electronamic tube tester manufactured by Precision
Apparatus Company. Will copy and return.
R. L. Pregitzer
601 Second
Webster City, Indiana 50595
Needed: Schematic and parts list, or other information, for old Philco table -model radio, Model 60,
Chassis T13841.
Bernard Grupe
3012 Highland Drive
Cary, Illinois 60013
ELECTRONIC SERVICING
Needed: Schematic for Superior Instruments
signal generator, Model TV-30.
Holiday Electronics
3100 S. E. Lake Weir Avenue
Ocala, Florida 32670
Needed: Schematic and scope tube (CRT)
scope #158.
William J. Maida
Rt. 2, Box 471-H
Maitland, Florida 32751
1'V
for RCA
NEW! An absolutely LEGAlway
LEENEW!
to Pull In Distant,Weak
CD Signals!
Needed: Schematic and servicing instructions for
McMurdo Silver signal generator Model 906. Will
buy, or copy and return.
Joseph N. Sealey
5336 Klamath Drive
Sacramento, California 95842
Needed: Flyback for Admiral color TV chassis
#4H10NC 57-3, part #79-130-2.
Welch's Radio and TV Repair
616 Valencia Drive
Belleville, Illinois 62223
For Sale or Trade: Simpson 260 VOM in A-1
condition. Would consider trade for short-wave
receiver or scanner.
D. K. Schmidt
1031 Terrace
Brainerd, Minn. 56401
Needed: Schematic
chassis #CR242AA.
for an old Magnovox radio,
Arnold G. Schmidt
Route 3
Jamestown, N.D. 58401
CB
MAKES
INCOMING
SIGNAL VOLTAGE
10 TIMES STRONGER
PERMITS "WALL-TO-WALL"
CB RECEPTION FROM MUCH
GREATER DISTANCES
AUTOMATIC SWITCH
ACTIVATES PREAMP DURING
RECEPTION, BYPASSES UNIT
DURING TRANSMISSION AND
WHEN CB-XTENDER
AMPLIFIES AM AND
SSB
IS
TURNED OFF.
WITHOUT SWITCHING.
MORE THAN 20dB GAIN. LESS
THAN 2dB NOISE FIGURE. 2-30MHz BANDWIDTH.
CONNECTS EASILY BETWEEN CB TRANSCEIVER
AND ANTENNA., NEG OR POS GROUND.
gCHEMTRONKS
INCORPORATED
45 HOFFMAN AVE
.
HAUPPAUGE, N
Y
11181
2
(516( 582 3322
Our business is improving yours)
For More Details Circle
(8) on Reply Card
For Sale or Trade: Sencore FS134 field -strength
meter, new with warranty for $220. Or take in trade a
working B&K portable multimeter.
Charles Helpsgarden
612 Range End Road
Dillsburg, Penn. 17019
Needed: Spring type motors in working condition for
RCA victrolas. Models W-100 and W -XI. State
price.
John A. Sheaffer, Jr.
RD #1, Box 79
Tower City, Penn. 17980
GO
DIGITAL,
GO DANAMETER
Needed: Manual or schematic for a Monarch Monaco
radio, Model #SMX-77A. Also, manual or schematic
for an Analab oscilloscope, type 1100. Will buy, or
copy and return.
R. L. Johnson
Rt. 2, Box 2299D
Elk Grove, Calif. 95624
(The New VOM For Today's Needs.)
Needed: Schematic and an up-to-date tube chart for
Supreme tube tester, Model #600-61B. Will pay for
information.
Philip Saullo
788 Alter St.
Hazleton, Penn. 18201
July, 1976
0.25% Accuracy
Full Overload Protection
Really Drop -Proof
Full One Year Battery Life
DAnA
Dana Laboratories, Inc.
2401 Campus Dr, Irvine, Ca 92715, (714) 833-1234
For More Details Circle (9) on Reply Card
11
Model 123A CB radio from E. F. Johnson (Phatofact CB -47) is used as an example of modern synthesizer design.
CB SIfiltIleSIlerS...
Theory and
1iOld1
i
ing
By Marvin J. Beasley, CET/Land Mobile Regional Manager, E. F. Johnson Company
23 -channel synthesizer oscillators probably are the most-complicated
and least -understood circuits in CB transceivers. But troubleshooting can
become routine, after you know how they operate.
12
ELECTRONIC SERVICING
A synthesizer oscillator circuit
makes possible full 23 -channel CB
operation at reasonable cost. In
fact, a receiver with standard
crystal oscillators for 6 channels
would cost about the same as a
similar one with a 23 -channel
synthesizer. Cost saving with the
synthesizer is possible because each
crystal is used for several channels.
IF. That totals two crystals per
you need to have a general idea of
channel.
Therefore, a CB receiver without
a synthesizer would require 46
crystals to cover all 23 channels by
the conventional method.
Typical synthesizers use any
number of crystals between 10 and
14, to control both transmitting and
receiving frequencies. The economy
of 14 versus 46 is obvious.
Best understanding of synthesizers comes from comparing them
against the conventional circuits.
Crystal oscillators
Crystal oscillators are a necessity
for transmitting, and a convenience
for receiving. That's because the
FCC specifies a frequency accuracy
of only ±.005% (50 parts -per -million, or PPM). The same crystal
cannot be used for both transmitting and receiving, since the receiving oscillator frequency must be
higher or lower than the channel
frequency by the frequency of the
the circuits.
Overtone Oscillators
Shortly afterward, the CB industry changed to overtone oscillators,
which have outputs at the third
harmonic, without any extra stages.
Typical circuits are shown in Figure
2.
Servicing overtone oscillators
Here are some suggestions for
servicing oscillators having overtone
circuits.
Frequency Multipliers
Don't make the mistake of
The first Class D Citizens Band
transceiver radios (in 1958) used
low -frequency crystal oscillators
with doubler or tripler frequency
multipliers to reach the final channel frequency (see Figure 1).
Many of these old machines still
are in use and needing service, so
viewing a third -overtone oscillator
as merely a fundamental oscillator
with an output tank that's tuned to
the third harmonic. In fact, the
output is not quite three times the
frequency. A 9 -MHz crystal would
have an output near (but not
precisely) 27 MHz. So, be certain
ANTENNA
0
--j
RF
AMP
T
MIXER
IF
DETECTOR
TRIPLER
CHANNEL
CRYSTAL
o
o
o
o
IoF-o+-
OSC
o
a
AUDIO
AUDIO
AMP
SPEAKER
a
POWER
AMP
(MODULATOR)
MIC
CHANNEL CRYSTAL
o
o
o
o-
o
o
OSC
DOUBLER
DOUBLER
RECEIVE CH.
11
OSC FREQ
TRANSMIT CH.11 OSC FREQ
RF
POWER
RF
OUTPUT
AMP
27.085 MH
- .455 MHz
27.05 MHz
-
-
8876.666 kHz
6771.25 kHz
SYNTHESIZERS
Fig. 1 A block diagram illustrates an older CB transceiver with separate oscillators that operated
at low frequencies which
were doubled or tripled to reach the CB band.
July, 1976
13
the crystal is designed for the CB
set you're working on. Do not rely
on the frequency marked on the
crystal.
A crystal cut to the specs of one
manufacturer probably would oscillate in a radio of another brand,
but the frequency might be out of
tolerance, or the oscillator could be
slow starting or overly-sensitive to
temperature changes.
In some overtone circuits, mis tuning of the output circuit can
cause the frequency to jump out of
tolerance.
A
RECEIVE OVERTONE
OSCILLATOR
B2700Q
TO
MIXER
39 pF
o
o
o
o
180 pF
47052
frequency counter
CH.11
would show a wrong frequency, and
you might think that the crystal
was defective. However, a correct
replacement crystal would give the
27.085 MHz -.455 MHz
26.630 MHz CRYSTAL
B
TRANSMIT OVERTONE
OSCILLATOR
same wrong frequency before the
tank was tuned.
Of course, an incorrect output
coil also can produce a wrong frequency. I remember the time I
wasted an extra hour by installing a
wrong inductor in an oscillator.
Synthesizer Oscillators
definition, synthesizing is
forming a whole by combining
By
parts. In this case, it means obtaining a third frequency by combining
CH.11 CRYSTAL 27.085 MHz
B
Fig.
RF
AMP
2
These are two typical oscillators using a third -overtone circuit.
IF
MIXER
-
DETECTOR
A
T
oi
AUDIO
AUDIO
SPEAKER
POWER
AMP
AMP
(MODULATOR)
MIC
HIGH CRYSTALS
Y1 o
Y2 o
Y3 o
y4 0
HIGH
OSC
Y5 o
Y6 o
LOW CRYSTALS
SYN
MIXER
27
MHz
FILTER
Y7 o
PRE -DRIVER
Y8 o
RF
RF POWER
DRIVER
AMP
OUTPUT
Y9 o
Y10 o
Y11 o
Y12 o
LOW
OSC
4
TRANSMIT CRYSTALS
4 RECEIVE
CRYSTALS
Y13 o
Y14 o
SYNTHESIZERS
signal for both receive and
Fig. 3 This is the block diagram of a CB radio that has a synthesizer to furnish the oscillator
switches.
of
the
place
the
take
diodes
transmit functions. In the actual circuit, switching
14
ELECTRONIC SERVICING
two frequencies. That sounds like a
mixer; and it is one type.
Combining two signals of different frequencies in a non-linear
mixer produces an output with four
frequencies: the original two, plus
the sum of the two, and the difference between the two; for example, mixing 20 MHz and 7 MHz
gives 20 MHz, 7 MHz, 27 MHz,
and 13 MHz. Now if you want 27
MHz, something must eliminate the
others. That is done by filters or
tuned circuits at the output.
Ten crystals in a 6 -by -4 arrangement could synthesize 24 channels,
one more than needed. Only 4 more
are necessary to crystal -control the
receiver.
Analyzing A
Synthesized Transceiver
Here are some general facts.
Except for the oscillator crystals,
the tunings of both the transmitter
and the receiver are not changed
Features of a modern synthesized
CB transceiver are shown by the
for the various channels. The
block diagram of Figure 3. Some spread of frequencies is narrow
details are symbolic rather than enough to permit one adjustment
actual. For example, newer radios for all channels.
don't have a multi -element transThere are 6 "high" crystals, 4
mit/receive switch (or a relay used "low" crystals for receiving, and 4
as a switch). Instead, switch con- other "low" crystals for transtacts in the microphone determine mitting. The channel switch always
the conduction or non -conduction selects three crystals for each of the
of diodes which function as 23 channels. The high -oscillator
switches.
crystal is active all the time (for
Circuits of the E. F. Johnson both transmitting and receiving).
Model 123A will be used to explain One of the low -oscillator crystals is
the operation of typical synthe- connected during transmission, and
sizers.
the other is used during reception.
26.965 MHz
SYNTHESIZER
RECEIVER
TUNED
RF
TUNED
REC
CIRCUITS
AMP
CIRCUIT
MIXER
RECEIVING
455 kHz TO
I
F'S
.01
POSITIVE VOLTAGE
Ï2.2
NON-CONDUC
I
KW
TURNS ON CR8 & CR14
NG
33052
Q5
2.2KW
LOW
CI
OSC
-
DC
g+
Q6
SWITCH
NO DC
6.190
MHz
I
-
26.510 MHz
FOR CH.1
820 pf
CONDUCTING
Q6 NON -CONDUCTING
-320 pF
680W
33052
CONDUCTING
.-.01
HIGH OSC
'V\/v--44-
C
8+
1
39 KS2
180 pF
6.8 KO
NON-
SYNTHESIZER
CONDUCTING
MIXER
c
TUNED
.01
CIRCUITS
g+
120W
220W
SYNTHESIZERS
Fig. 4 Diode switching and receive signal flow of the Johnson Model 123A
is shown in this block diagram. Notice that
the "low" signal is applied to the base of Q14, the mixer, and the "high"
signal is injected at the emitter. Q6 is used as a
switch to control the conduction of CR8 and CR14. CR8 connects the base
of Q5 to the receive crystal that has been
selected by the channel switch, and CR14 channels the output of the synthesizer
mixer to the mixer of the radio receiver.
July, 1976
15
Selection between these two is done
by diode switching of the transmit/
receive function, and not by the
channel switch.
Synthesizer during receive
Signal -flow paths during reception are diagrammed in Figure 4.
Nothing in the high oscillator is
switched except the crystals. Diode
conduction determines which low
crystal of two is in use, and other
diodes route the synthesizer output
from the tuned circuits to receiver
or transmitter.
In the receive mode, the microphone switches remove the +9.99 volt power, that supplies the base of
Q6 through a 22K resistor. Without
forward bias, Q6 draws no C/E
current, so the collector voltage
rises. Some of this collector voltage
goes through R17 and forward
biases CR8, which then connects
crystal Y5 (for Channel 1) to the
base of 05, the low oscillator and
also furnishes forward bias for Q5.
At the same time, part of the Q6
collector voltage through R43 forward biases CR14, thus allowing
the output from the synthesizer to
go to the receiver mixer.
Mixing of the 6.190 MHz low
signal with the 32.700 high signal
produces 26.510 MHz at the synthesizer output. And this signal beating against the 26.965 Channel 1
input signal in the mixer supplies
455.KHz for the IF amplifiers.
Synthesizer during transmit
Figure 5 gives the signal
flow
during the transmit mode. The
high oscillator circuit (and crystal)
is the same as during receive.
Q6 now has sufficient forward
bias for saturation; the collector
voltage is nearly zero, thus turning
off CR8 and CR14.
However, the same microphone
keying supplies a positive voltage
through R21 to forward bias CR7
so it connects Y1 crystal to the base
of Q5, and also furnishes forward
bias. Part of the same keyed voltage
goes through R59 to force CR15
into conduction, thus channeling
the output of the synthesizer to the
transmitter RF amplifier.
Mixing the 5.735 -MHz low signal
with the 32.700 -MHz high signal
produces the 26.965 -MHz carrier
that's needed for the transmitter on
Channel 1.
Other channels operate the same
way, but with different combinations of crystals.
Servicing Synthesizers
Much of the information you
need to troubleshoot this kind of
synthesizer is found in the next few
charts. Always keep in mind the
way the signals are mixed, because
that knowledge plus the frequency
charts often will pinpoint the
defect.
POSITIVE VOLTAGE
SYNTHESIZER
FOR
TURNS ON CR7
AND CR15
2200 Q
TRANSMITTING
FROM TIR KEYING
CONDUCTING
ODC
LOW OSC
SWITCH
22 KO
QS
3300
CI
V
ZERO VOLTAGE TURNS OFF
B
CR8 AND CR14
-
Y1
5.735
820 pF
NOT
MHz
27000
(t
SATURATED
'ONDUCTING
I
320 pF
680Q
3300
-.01
NOT
HIGH OSC
MA.-.1-
CONDUCTING
8+
22000
39 KO
180 pF
SYNTHESIZER
68000
4700
CONDUCTING
MIXER
E
I(
.01
.01
TUNED
CIRCUITS
180
TO
TRANSMITTER
DRIVER
26.965 MHz
PF
CH.1
i0
68000
8+
1200
2200
SYNTHESIZERS
in the transmit condition. Positive
Fig. 5 This schematic shows the same synthesizer with switching and signal flow
low -frequency transmit crystal that
to
the
of
Q5
base
the
connecting
conduct,
CR7
to
forces
voltage from the mike switch
feeds
the output of the synthesizer to
which
has been selected by the channel switch. The same voltage keys -on CR15,
stage.
the transmitter driver
16
ELECTRONIC SERVICING
SYNTHESIZER FREQUENCIES
CHANNEL
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
RECEIVE
HF CRYSTAL
LE CRYSTAL
RECEIVE
OUTPUT
TRANSMIT
LF CRYSTAL
TRANSMIT
OUTPUT
32.700
32.700
32.700
32.700
6.190
6.180
6.170
6.150
26.510
26.520
26.530
26.550
5.735
5.725
5.715
5.695
26.965
26.975
26.985
27.005
32.750
32.750
32.750
32.750
6.190
6.180
6.170
6.150
26.560
26.570
26.580
26.600
5.735
5.725
5.715
5.695
27.015
27.025
27.035
27.055
32.800
32.800
32.800
32.800
6.190
6.180
6.170
6.150
26.610
26.620
26.630
26.650
5.735
5.725
5.715
5.695
27.065
27.075
27.085
27.105
32.850
32.850
32.850
32.850
6.190
6.180
6.170
6.150
26.660
26.670
26.680
26.700
5.735
5.725
5.715
5.695
27.115
27.125
27.135
27.155
32.900
32.900
32.900
32.900
6.190
6.180
6.170
6.150
26.710
26.720
26.730
26.750
5.735
5.725
5.715
5.695
27.165
27.175
27.185
27.205
32.950
32.950
32.950
6.190
6.180
6.150
26.760
26.770
26.800
5.735
5.725
5.695
27.215
27.225
27.255
NOTE: All frequencies in MHz
Chart
1
Chart
1
gives the five frequencies
t'or each of the 23
channels of the
Johnson Model 123A. However,
much of the service data lists only
the Y crystal numbers; so Chart 2
gives Y -numbers versus frequency
of the 14 crystals. With both charts
you can easily run down the location and frequency of all the
crystals.
Servicing by bad channels
If the transmitter is dead on all
channels, but the receiver is okay,
the problem is likely to be in the
transmitter, not the synthesizer. By
the same reasoning, if the receiver
is dead on all channels, but the
transmitter is normal, the defect
probably is in the receiver, not the
synthesizer. Of course, there are a
couple of "howevers". However, the
failure of a switching diode in the
synthesizer could kill either the
transmitting or the receiving function without affecting the other.
And a defect in the T/R switching
also might eliminate one but not
July, 1976
the other.
Other symptoms
But if only a few channels are
Here are some tips for troublemalfunctioning, it's certain to be a shooting synthesizers:
problem in the, synthesizer; and a Both transmitter and receiver are
crystal (or the switch contacts to the dead, but the high and low oscillacrystal) must be the first suspect.
tors have correct frequency and
Continuing with logical reason- amplitude. Probable cause-mixer
ing, a dead crystal can cause no
less than 6 channel functions to be
wrong. For example, a defective Y1
transmit crystal kills channels 1, 5,
9, 13, 17, and 21 on transmitting
CRYSTAL FREQUENCIES
only (a total of 6 functions). However, a dead Y9 high -frequency
Y1
5.735 MHz
LF transmit
crystal eliminates channels 1, 2, 3,
Y2
5.725 MHz
LF transmit
and 4 on both transmit and receive,
Y3
5.715 MHz
LF transmit
a total of 8 functions.
Y4
5.695 MHz
LF transmit
Y5
6.190 MHz LF receive
Chart 3 has been compiled to
Y6
6.180 MHz LF receive
take away most of the calculations
Y7
6.170 MHz LF receive
(or guesswork) in determining which
Y8
6.150 MHz LF receive
crystal is defective. To use it, first
Y9
32.700 MHz HF
try all 23 channels for both transY10
32.750 MHz HF
mitting and receiving, and write
Y11
32.800 MHz HF
down which channels are bad for
Y12
32.850 MHz HF
each. Next, go to Chart 3 to see if
Y13
32.900 MHz HF
your listing of dead channels corY14
32.950 MHz HF
responds to any of the conditions
listed.
Chart 2
17
transistor (Q14)
is
SYNTHESIZER CRYSTAL TROUBLESHOOTING
inoperative.
Transmitter is okay, but the
receiver is dead on all channels.
Probable cause -switching diode
CR8 or CR14 is open.
Receiver is okay, but the transmitter is dead. Probable cause
switching diode CR7 or CR15
Channels
Inoperative
1, 2 3, and 4
5, 6. 7, and 8
9, 10, 11, and 12
13, 14, 15, and 16
17, 18, 19, and 20
21, 22, and 23
1, 5, 9, 13, 17, and 21
2, 6, 10, 14, 18, and 22
3, 7, 11, 15, and 19
4, 8, 12, 16, 20, 23
1, 5, 9, 13, 17, and 21
2, 6, 10, 14, 18, and 22
3, 7, 11, 15, 19
4, 8, 12, 16, 19, and 23
-
is
open.
Improper operation of the low
oscillator, although the DC voltages
are normal. Possible cause -Q6 is
open or shorted (Q6 is used as a
switch, open on receive and shorted
on transmit, so with a bad Q6 one
function should be normal, and
both transmit and receive crystals
would be connected together during
the other function. Therefore, check
for almost zero volts at collector of
Q6 during transmit, and about +9
volts during receive. If the voltage
doesn't change, Q6 is defective).
Baffling symptoms can be produced by a shorted switching diode
(CR7, CR8, CR14, or CR15). For
Chart
Fig.
example,
18
Faulty
Crystal
X
X
X
X
Y9
Y10
X
X
X
X
X
X
X
X
X
Yi
Y12
Y13
Y14
Y5
Y6
Y7
Y8
X
X
X
X
Y1
X
X
Y2
Y3
Y4
X
a
shorted CR7 would
permit normal transmit but wrong
receive. One of my worst service
jobs was caused by a shorted CR8
6
8
Transmit
lnooerative
3
All the crystals are soldered to the channel switch,
and it's impossible to unsolder some of them without removing the switch.
Fig.
Receive
Inoperative
Only one connection requires unsoldering.
which paralleled both crystals when
in the transmit mode. The output
was on the wrong frequency, but
the synthesizer output seemed
Fig. 7 The knobs slide off the flattened shafts, exposing
the nuts on the controls. The large nuts, and two screws
at each edge of the panel, must be removed to free the
front panel.
Fig.
9
Two screws hold the meter to the front panel.
ELECTRONIC SERVICING
to be correct. Evidently both frequencies were there at the same
time, and this confused the frequency counter. Service tip-check
the switching diodes first. They are
high -speed -switching silicon types.
Do NOT use germanium.
Access To The Crystals
After your diagnosis has indicated a defective crystal, you must
decide how to remove the crystal.
They are soldered, and many are
not readily accessible. (Figure 6).
With the Johnson Model 123A,
the most -workmanlike way (and
probably fastest in the long run) is
to disassemble the machine, as
shown in the following pictures.
Pull off the three front -panel
knobs (Figure 7). Remove the nuts
holding the two controls, and also
remove two screws at each end of
the front panel.
In Figure 8, the screwdriver
points to the lead of a panel
indicator, the only part that re- bad synthesizer can affect either
quires unsoldering.
receiving or transmitting, or both.
Unscrew the screws holding the
Use a frequency counter to check
meter to the panel (Figure 9), then the individual oscillators, and also
remove the front panel, as shown in the synthesizer output signal at
Figure 10.
CR14 and CR15 (following the
Remove the two screws holding tuned circuits). But, confusing or
the switch assembly to the circuit wrong readings might be obtained
board (Figure 11).
in the mixer circuit, or from any
Now the switch swings freely source having two or more RF
against the connecting wires, allow- signals together.
ing inspection or repairs to any side
A dead crystal will affect a total
of the switch (Figure 12).
of either 6 or 8 transmit/receive
One final hint, use caution when functions, in synthesizers similar to
you remove an unfamiliar trans- the one in the Johnson Model
ceiver from its case. The speaker 123A. A defective channel switch
might fall out, as shown in Figure could kill just one channel.
13, and damage the cone.
If the symptoms do not indicate
a bad crystal (or some other deComments
finite defect), check the operation
Servicing synthesizers should not of the T/R switch in the microbe difficult, if you keep these points phone, the Q6 keying circuit, and
in mind:
all four of the switching diodes.
A synthesizer is used to supply
Use the charts to determine
the oscillator signal for both trans- which crystal is suspected of being
mitting and receiving; therefore, a bad.
Fig. 10 The front panel now can be placed aside.
Fig. 12 The wires permit movement of the switch, and yet
allow the radio to be operated for tests.
July, 1976
Fig. 11 Removing the two screws marked by arrows frees
the switch/crystal assembly so you can move it as
necessary to reach the suspected crystal or switch
contact.
Fig. 13 When you remove the radio from the case, watch
for the speaker, which might drop out and injure the
cone.
19
Part 2/By Norman H. Crowhurst
SERVICING
ELECTROPIC
ORGANS
Certain facts must be known about an
organ before you can troubleshoot it
logically. Here is the essential information about eleven popular brands of
organs. Next month, specific methods
of analyzing organ defects will be
started.
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What Brand? How Old?
Let's assume that the owner of
an electronic organ has called you
to examine it and repair some malfunction. You don't have a schematic or any data to guide you. No,
don't give up and refuse the call.
You might be surprised at how
many repairs can be made without
service data.
Older organs used many tubes,
types you might have yet in your
old stock. Some popular numbers
were 6L6G, 6V6G, 6SN7, 12AX7,
12AU7, and 5U4G. All tube testers
list these old tubes, and identifying
or replacing them should cause no
problems.
The multitude of switch contacts
under each keyboard cause typical
defects, such as notes that sound
continually, or not at all.
Beyond these generalities, it is of
vital importance that you know
some facts about each organ. Does
it use the oscillator/divider system
of generating the notes, with each
octave depending on the divider
above it? Or, is each note supplied
by a separate oscillator? A few
models use frequency synthesis in
which the fundamental and selected
harmonics (all sine waves) are combined in the desired ratios.
The next essential is knowing
whether the keying switches,
couplers, and stops handle the
audio of the notes directly, or operate DC voltages to key the notes
and functions.
In addition, some organs (including Hammond) have important
moving mechanical parts, such as
motors, shafts, or belts, that are essential for generating the tones or
for adding vibrato. A frozen bearing in a motor does not require a
schematic; and many other defects
can be found visually.
Details can be learned later.
Right now, we will examine general
features of the better-known brands,
listed in alphabetical order.
Allen Organs
By the late '60s, Allen was using
one transistorized oscillator for
each note. (We have no data on
older models.)
These oscillators were inactive
until a note was pressed, supplying
voltage to the transistor. Couplers
were provided so the same key
could control more than one tone
July, 1976
0:P
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P
(B)
Fig. 1 Allen organs have individual oscillators for each note. They do not
operate until the supply voltage is switched on. Two variations are shown.
another manual), and
diodes gave decoupling to prevent
spurious keying between the various
coupled notes. Each oscillator was
tuned, and two different methods
were used, as shown in Figure 1.
Light -controlled relays were used
extensively in the voicing circuits
(Figure 2). Voltage from the DC
supply could be switched to a light
bulb inside a light -tight box, which
also contained a cadmium -sulfide
or cadmium-selenide cell. When the
light was not lit, the resistance of
the cell was very high, acting as an
open circuit. Light caused the cell
resistance to decrease, perhaps to a
few thousands or hundreds of
ohms, thus functioning as a closed
switch.
Switching with light-sensitive cells
has another advantage, in addition
to the DC control -voltage circuits
that are immune to noise and hum.
The change in sound level is not
instantaneous. A resistor in series
with the incandescent lamp bulb
(octaves, or
pressed and the stops activated.
Secondly, after the voltages reach
the oscillators or the stop relays, is
the operation normal there or not?
These organs were designed to be
highly reliable. So, most service
work involves repairing bad switching contacts and replacing shorted
diodes.
Newer Allen organs (probably too
new to require any service) are even
more complex. Every musical note
is synthesized at the time of playing, by digital techniques. The
digital information is converted to
audio waveforms by two digital -to analog converters in each organ.
reach maximum brilliance. When
light reaches the CdS cell, the resis-
Baldwin Organs
Earlier Baldwin organs had 12
generators, each with a tube oscillator for the top octave, followed by 5
dividers using tubes (Figure 3).
The output waveform from each
divider was a rounded sawtooth.
But square waves were made by
adding 50% amplitude of inverted
4' tones to the 8' notes. Voicing was
done by low-pass, high-pass, and
resonant filters, as shown in Figure
tance decreases moderately fast;
4.
however, the resistance increase is
much slower after the light is
Instead of on/off switches under
each note, tiny flat variable resistors were used. This provided a
gradual build-up and decay of the
notes, since some time is required
to 'move the keys, and it eliminated
all keying clicks. Similar construction was used for some expression pedal circuits and stop switches.
The generators had double -triode
tubes. Octal -based 6SN7 tubes were
used at first, followed by 9 -pin
lengthens the time required to
turned off. These time delays
virtually eliminate any pops or
clicks that often are caused by instantaneous on/off action from conventional switches.
Circuits of Allen organs are quite
sophisticated. To trace a fault, you
need to prove whether or not the
DC control voltages go where they
should, as determined by the keys
21
slowly, when desired. (Figure 8).
Conn Organs
12AX7 types.
Through many other changes,
When Baldwin changed to transistorized circuits, the basic philosophy of master -oscillators and
dividers was continued. However,
the dividers provided square waves,
rather than sawteeth.
Square waves have only odd numbered harmonics, without even
ones. When tone colors with even numbered harmonics are desired,
50% level of the next higher octave
is added, plus 25% amplitude of
the second higher octave. This provides a useful simulation of saw tooth sounds.
Artificial reverberation and percussion or sustain features were
used in many versions.
Conn has maintained a policy of
having a separate oscillator for each
note of the organ.
Keying of the tube models was
achieved by switching the B+, but
with decoupling (Figure 5) to eliminate clicks and thumps. Multiple
contacts under the keys coupled to-
gether the various octaves and
manuals. The supply rod for each
coupler or octave could be rotated
by the stop (Figure 6) so the contacts coming against it when a key
was depressed would touch either
the insulated side of the rod (stop is
oft), or the bare metal to make
contact (the stop is on).
When Conn changed to transistor
oscillators, all oscillators (Figure 7)
were kept running constantly, and
keying was done in two ways. Pulse
output waveforms were keyed as
audio (the stop filters removed most
of the clicks), and the flute waveforms (more susceptible to keying
clicks) were keyed by changing the
bias of a transistor.
Keying the bias of flute transistors also made possible a sustain
action, so the tones died away
Latest -model Baldwin organs
incorporate Large -Scale -Integration
(LSI) components to supply rhythm
accompaniment (drums, cymbals,
etc.), and percussion voices with
automatic strumming or arpeggios
(playing the notes of a chord in
succession into higher or lower
octaves).
The keyb3ard notes have a single
switch under each, supplying a DC
voltage for diode keying. Coupling
is done with FET's.
MV. FROM
MELODIA
Conn also has rhythm generators
using LSI circuitry.
Gulbransen Organs
Gulbransen organs have used
solid state longer than most manufacturers. Earlier models had a
oscillator for each note, and with
keying similar to that of some
Conns.
Later, various models have been
changed to the master -oscillator/
divider type of generator.
Some Gulbransen circuits are
unique, so we will defer a more -
detailed coverage until another
month.
Hammond Organs
the pioneers in the
field of electric and electronic organs, Hammond has manufactured
some unique designs. First was the
model with "tone wheels" to generate sine waves electro -mechanically,
and with tubes only for amplification. At the time, Hammond built
clocks, so it was natural that the
organ have an oversize synchronous
clock motor to rotate the generators
(Figure 9).
As one of
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Fig. 3 Six octaves of one note are produced b4 each of 12 generators, such as this, in older tube -equipped Baldwin
organs. These dividers are blocked -grid oscillators, which are synchronized by magnetic coupling between the blocking
transformers. Output waveforms are sawteeth, shaped by the capacitors C4, C5, etc. The output signals come from these
capacitors, but are decoupled by the resistors labeled (2). If a divider begins to gurgle or thump, use a resistor -sub box
across the corresponding capacitor and find the highest value that removes the noise. (The capacitors tend to increase
with age, and this restores the original time constant.)
Outwardly, the distinctive feature
of these models was the many
"drawbars", which provided adjustments for the different tone colors.
The musical tones were made by
combining fundamental and selected harmonics (all sine waves) in
the Harmonic Synthesis method.
The drawbars (with plastic ends
colored white, brown, and black)
determined the amplitude of the
corresponding fundamental and
harmonics, according to how far
out they were pulled. Zero and
eight degrees of amplitude were
supplied.
In the first models, the drawbars
switched each sine wave to one of
eight bus bars, which in turn went
to a tap on the input transformer.
Later versions changed to a tapped
resistor instead of a tapped transformer, and added two contacts
separated by a low -value resistor.
This way it was impossible to reach
a
sold in large quantities. One of the
sales features was that tuning never
was necessary (of course, it was
impossible, because of the motor
drive). Peculiar things can happen
during those rare times when the
motor doesn't run at synchronous
speed. For example, during a
church service the lights blinked
from a thunder storm. But when
the organist next started to play,
the music was about five notes flat!
Of course, it still was in tune with
itself, but the motor had locked to
a false sync speed. Restarting it
cured the problem.
SAWTOOTH
INPUT SIGNALS
ENGLISH HORN 8'
SAXOPHONE 8'
SALICIONAL 8
dead spot between positions
(which was an annoyance with the
previous models).
Even today, these drawbar -tone wheel models are the ones people
associate with Hammond, for they
July, 1976
TO
PREAMP
Fig. 4 These are examples of the stop filters
used in some models of Baldwin organs.
23
Later models added electronic/
mechanical vibrato. The signals
were swept in phase by going
through a series of LC filters, with
the output taken by a scanner unit
(also operated from the motor).
Instantaneous keying adds vertical rising and falling sides to the
sine waves at turn -on and turn-off
times. These fast rise -times sound
to the ear as clicks. To minimize
clicks, and because organ music
sounds more natural with echoes,
artificial reverberation using springs
as time -delay units soon became
standard on Hammonds.
Novachord
One of the first oscillator/divider
types of organ was the Hammond
Novachord, now only a memory.
One large keyboard was supplied
with simple rotary controls for filter
circuits to modify the basic tone.
Keying tubes were used so both the
attack and decay time could be
changed. Another unique idea was
a separate (mechanical) vibrato for
each of the 12 semitones. This gave
a chorus effect to minimize the too perfect electronic sound.
Unfortunately, the model suffered
the fate of many ideas born before
its time, and few were sold. The
organ was large, heavy, complex,
and difficult to service. As I recall,
about 200 large octal -based tubes
were used. Today, many of the
space-age organs incorporate some
of these features, but with IC's to
keep the size and heat within
limits.
Chord organ
For those persons who are a little
afraid of a full organ with several
keyboards and "all those pedals",
Hammond offered the Model S-6
Chord Organ. The single keyboard
(Figure 10) played only the highest
note pressed at any time, with
rocker -type stops to change the
octaves and timbre. At the left of
the keyboard were the chord buttons, complete with an accent bar.
Frequency dividers received signals
from the root note of each chord,
and the musical fifth (in key of C,
the root is C, and the fifth is G),
and these "pedal" signals were
played by the two pedals. The left
pedal sounded the root, and the
right one gave the fifth.
Such an organ is easy to play,
but it posed some rigid limitations
on the possible musical variations.
Consequently, many new owners of
all makes of chord organs shortly
decided that being an organist was
not their thing, and abandoned the
machine. Or, they acquired some
skill and realized they wanted more
variety, then traded the chord
organ for a full model.
Oscillator/divider
just under 4 MHz, determines the
tuning of the entire organ. Multiderivative dividers using LSI components supply all notes of all
frequencies.
Two types of vibrato are available. One varies the oscillator frequency, so all notes warble together, and the other changes the
apparent frequency of the audio,
following the tone synthesis and
keying, by varying the phase alternately to each side of zero. This
latter system permits a split vibrato;
for example, to have different
amounts of vibrato for certain stops
or individual keyboards.
Kimball Organs
We have data only on the newer
Kimball organs. Although the basic
system is a master-oscillator/divider
type, the circuits are complex, with
digital and logic circuitry used
extensively. Included are OR and
NAND gates, flip-flops and op am ps.
These principles are new to organ
technology, so we will describe the
details in a later article.
Hammond's first solid-state organs had a conventional appearance, tilting stop tabs, and oscilla-
Kinsman Organs
Master-oscillator/divider circuits
tor/divider tone generators. Of were used in Kinsman organs that
course, servicing is similar to others used tubes. The unique difference
was that the dividers used neon
having the same general circuits.
bulbs. Figure 12 shows a 5 -octave
generator. Probably you can reDigital Models
cognize easily the basic neon -bulb
Hammond
Although the latest
models (Figure 11) resemble the oscillator circuit, modified for
tone -wheel versions (complete with locked oscillator operation. Two
drawbars and reversed -color pre- neon bulbs are used rather than
sets), they also have stop tabs, and just one, to improve the locking,
the generators are out of the space and to isolate the output sawtooth
from the higher -octave signal that
age.
locks it.
A single oscillator, operating at
BUS BAR
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COUPLER RODS
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(B)
Fig. 5 R2 and
voltage of Conn
nate clicks, and
and decay times
24
C3 filter the plate
oscillators, to elimito make the attack
more natural.
"On" position.
BAR
"Off" position.
Fig. 6 Many switch contacts are under each Conn keyboard. Depressing a note
makes contact when the coupler rod is turned with the metal side toward the
key -switch finger. The note cannot play when the coupler rod is turned with the
insulation toward the switch wire.
ELECTRONIC SERVICING
Neon bulbs have a long lifespan
and seldom fail. But if you should
need to replace one in a Kinsman,
the best bet probably would be one
of the small ones used as indicator
lights on panels (see Figure 13).
These have an internal current limiting resistor, which must be
removed or shorted out. Also, new
bulbs should be artificially aged to
improve the stability. Through a
470 ohm resistor, apply 120 volts of
line power to the bulb for two or
three seconds. Repeat the procedure
after a few minutes, to allow the
bulb to cool. This should prevent
any extreme changes later.
Lowrey Organs
Tube -equipped Lowrey organs
were of the master-oscillator/divider
PULS
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Fig. 7 These two examples of Conn oscillators show how two waveforms are
obtained from one type, and three waveforms come from the top -octave type
that has diodes acting as a doubler. These oscillators operate continuously. The
pulse outputs are keyed directly as audio, while the flute outputs are keyed by
transistors, with one transistor per note.
type, with Eccles -Jordan dividers.
One unusual feature was the DC
voltage at the key switches which
ionized neon bulbs. Of course, neon
bulbs are essentially open circuits
when not ionized, and partial short
circuits when ionized. So, the DC
voltage ionized each neon bulb,
passing the audio signal to the stop filter circuits. (Figure 14).
When Lowrey began using transistors, the neons were replaced by
diodes. The lower operating voltages made the design of sustain
and percussion actions much easier.
The newer Lowreys have extensive LSI circuitry, with a master
oscillator operating in the megahertz
range, multiderivative count -down,
followed by dividers for the lower
octaves. The Automatic Orchestra
Computer (AOC), Auto -Wow, Symphonic Golden Harp, and Brass
Symphonizer are extra features of
fv
COLLECTOR VOLTAGE SUPPLY
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Lowrey.
Rodgers Organs
Rodger's organs have an oscillator (sometimes more) for each note
of every voice to provide realistic
pipe -organ tone.
These organs are superbly engineered, and are custom built to
order. Anyone who can afford a
Rodgers probably should contact
the factory if service is required.
Thomas Organs
The earliest Thomas organs were
small models using tubes, and each
oscillator provided 2, 3, or 4 adjacent notes. This reduced the number of tubes and components, but
July, 1976
8 The flute output from each Conn Oscillator is keyed by changing the bias
o` a transistor, as shown. C26 delays the change of bias voltage to eliminate
any clicks, and a fixed voltage through D4 determines the sustain time before
Fig.
the note dies away.
COIL OUTPUT TERMINAL
MAGNET
TONE
ONE
WHEEL
SIDE OF COIL GROUNDED
COIL
Fig. 9 Cider model Hammond organs made complex musical notes by combining s ne waves coming from small generators using "tone wheels", which
were turned at the proper speed by a synchronous motor. Tuning was neither
necessary or possible.
25
Introducing the
RCA Color TV
Test Jig Adapter.
Now you can update your older test jig-or
make your own-to service most color -TV
consoles including sets of 45 different
brands, whethertube, hybrid or solid state.
The RCA Color Test Jig Adapter 10J107
offers you the same key feature as the RCA
Color Test Jig 10J106: the unique horizontal and vertical matching transformer with
rotary selector switches. With them, you
can match impedances to a wide range of
TV receivers with just a single test jig. And
do so without the need for transformer
adapters and plug-in switch units.
The RCA Color Test Jig Adapter comes
with a Low -Impedance Deflection Yoke,
Yoke Extension Cable, Ground Lead and
Test Jig Yoke Cable. Imagine the increased profits you can gain for only the
small optional user price of $89.00.
RC,'
Test Jig Adapter
placed some limitation on the
chords that could be played.
Seventh chords, for example, have
two notes just two semi -tones away.
With these older model organs, the
two adjacent notes would require
lingering them in different octaves,
else only one of the two would
sound.
Later organs were transistorized,
with master oscillators followed by
dividers. From the dividers came
square waves, so octaves were combined to make a stair -step simulation of sawteeth, when even harmonics were desired.
Thomas has carried "unitizing"
of construction farther than have
most other manufacturers. Therefore, much of the servicing consists
of replacing blocks, or packages,
which contain various components.
Wurlitzer Organs
"The Mighty Wurlitzer" was a
byword in the days of silent pictures accompanied by pipe -organ
music. Perhaps it was natural, then,
Fig. 10 This is the Hammond Model S-6
chord organ. Such chord organs were
very popular for a time. Operation was
somewhat like that of an accordion, but
with the advantages of bass pedals,
vibrato, and many stops.
26
ELECTRONIC SERVICING
Introducing your
opportunity
to name it.
We need a name for the new RCA Color
Test Jig Adapter and you can be the one to
give it to us. It's simple for you to win this
beautiful RCA 25" ColorTrak Console TV
model GA 708 by coming up with the win-
ning name. There are 2 second place
prizes-RCA ColorTrak Table TV model
FA 475, and 10 third place prizes-Skil
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There's nothing for you to buy and you may
submit as many names as you like, but
each name must be on a separate entry.
Your RCA Test Jig Distributor has all the
details, including the entry forms you'll
need for all the names you're probably
thinking of. Get in touch with him and enter
the contest today.
Distributor and
Special Products Division
Fig. 11 The new Hammond Concorde
organ is similar in appearance to the
older models with tone wheels, but the
circuits are all -solid-state with IC's and
transistors. DC through the keyboard
switches controls the sine waves.
for some of the early Wurlitzer
home and church organs to have
reeds which were electronically
amplified. There is a limit to the
number of electrostatic pickups
that can be placed on each reed, so
such organs suffered from not
having many tone colors. However,
the timbres were very "musical",
especially when aided by electronic
vibrato produced by variable phase shifting.
When Wurlitzer changed to solidstate, the circuits were of the
oscillator/divider type, with flip-flop
dividers. In the larger models,
Wurlitzer has tried to improve the
"body" of electronic music, using
multiple types of vibrato (for example, the Spectra -tone rotating
speaker plus tremulant of lower frequencies), percussion (drums,
July, 1976
shh27
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Fig. 12 Kinsman organs are unique for us.ng neon bulbs in the dividers.
One generator of six octaves is shown in the diagram.
boom, etc.), reverberation, and external speakers.
Newest models use the count-
Electronic Organs, Volume
of servicing organs is in knowing
and understanding the types of cir-
2
(book 20754); covers second -generation models up to 1969 (the ones
needing the most service); it has
one chapter about how organs
work, and another about tuning
methods.
cuits.
For those of you who would like
down method from a 666-KHz
of
12
notes
detailed circuit information,
the
obtain
more
to
oscillator
the highest octave. And these then we refer you to a series of Howard
drive dividers for the lower octaves. W. Sams books:
LSI is used extensively.
Electronic Organs, Volume
(book 20188); first published in
Comments
One reason for this article is to 1960 and updated in subsequent
familiarize you with the terminology printings; it's now out of print, but
of organ repairing. Also, the facts some copies probably can be found.
about the specific brands should Most of the coverage is on tube make troubleshooting them much type organs, with a few transiseasier, because an important part torized models.
Electronic Organs, Volume
3
(book 21176); published in 1975;
describes circuits and features of
new models that have ICs and LSIs.
1
Next Month
Servicing methods are the subject
for coverage next month, with both
general and specific tips.
NOT/ GREEN
LOWER
MANUAL
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LOWER MANUAL
KEYBOARD
Fig. 13 If you need to replace a neon
bulb in a Kinsman, remove the base
from a small panel bulb, such as this
NE -20, and short across the series resistor that's inside the base.
28
PEAR
VIEW
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GI.OUP
14 Some Lowrey organs key the audio tones by applying DC voltage to
neon bulbs, which act as low -value resistors when they are ionized.
Fig.
ELECTRONIC SERVICING
c:IJD IR IIiNK
The
RIM
lighter side of servicing
By Max Goodstein
Several times in my life, I found
had talents above my electronic
abilities. For example, once I was
busy in a customer's living room
repairing the TV, when I heard a
frantic call from the lady of the
I
house. Quickly,
I
ran into the
kitchen to find a youngster with a
blank expression sitting at the
table. The lady demanded, "Yell at
him, he doesn't want to drink his
milk!" Obligingly, I snarled and
shouted, "Drink".
My compensation for this above
the -call -of-duty help was that she
paid my service -call -plus -tubes without any comments about the price.
From that time, I was the neighborhood "bogeyman", used by the
mothers to threaten their balky
children. They would say, "Eat
your cereal, or he will put you in
his box (red and black tube caddy)
and take you away."
Not long afterwards, I decided to
stop these extra services, but I
proudly can claim some credit for
the healthy teen-agers around
Flushing.
Many years ago, while I was
working on a b -w TV, a little boy
snuggled up to me. "Mister," he
asked, "what do you want to be
when you grow up?" At first, I
thought the question was cute and
funny. Later, the serious side
occurred to me. Probably there are
men in their late thirties who don't
have any goals in life.
Chicken soup has been recommended as a cureall for the ills of
mankind. However, it doesn't seem
to be very beneficial to electronic
equipment. I received a call from a
young man whose grandmother
accidentally spilled chicken soup
into the rear of a color TV.
Evidently, the engineers hadn't
given any thought to making the set
soup -proof, for I found an area of
the circuit board had been burned.
The grandson couldn't imagine how
the soup got from the kitchen to
the bedroom where the TV was located. Needless to say, this was an
expensive repair, and the woman
still asks me, "How could just a
little soup do so much damage?"
Sometimes the logic of laymen
is beyond comprehension. One
customer called, saying "Mr. Goodstein, I have the latest model allsolid -state color set, and it just quit
working. It's probably only a small
tube that burned out."
Incidents, such as these, continue
to surprise and amuse me.
July, 1976
29
www.americanradiohistory.com
Background
Another "hidden" signal has
joined the others that are included
in the composite video of color-TV
VIR PREVIEW
programs. Three horizontal lines,
during the vertical -retrace time,
now are reserved for VIT and VIR
signals.
At Last!
Automatìc Color
VIT Signals
Vertical -Interval -Test (VIT) signals have been used for years on
lines 17 and 18, or 18 and 19 of
each video field. These can have
several different waveshapes (page
16, March, 1975 Electronic Servicing) as needed to evaluate frequency
response, overshoot, amplitude
By Carl
Babcoke
article "Goodbye, Color Controls", starting on
page 15 of ELECTRONIC SERVICING for March of
1975, the prediction was made that future color -TV
receivers would have NO color controls, or would
have them hidden because they would be needed so
seldom. The VIR signal, allowing the TV stations to
make continuous adjustments to the color signal,
was to make this breakthrough possible. Now the
General Electric company has made that prediction
come true, even before the TV stations have taken
full advantage of VIR. Not only does the GE VIR
system correct for color errors originating before the
signal leaves the transmitting antenna, but it also
corrects any receiver deficiencies. In a later issue, we
will present a more -detailed analysis of the circuit
operation.
In the
linearity, and other characteristics
of: network lines; studio -to-transmitter -links; video-tape recorders;
or complete transmitters.
VITS are not associated with any
certain program; they can be keyed
out and new ones inserted as often
as required, and seldom are they
used to adjust an individual program.
VIR Signals
Vertical -Interval -Reference (VIR)
signal (there's only one kind) supplements VITS, but does not replace them. The VIRS waveform
(Figure 1) is simple, because it is
designed to test only the black re-
ference, luminance reference,
chrominance reference, and the
blanking level.
VIRS is added to the video of
CHROMINANCE
IRE
REFERENCE
UNITS
90
70
SO
- PROGRAM
COLOR
BURST
iii
20
50
LUMINANCE
BLACK
REFERENCE _.
REFERENCE
7.5
--\\- BLANKING
LEVEL
IE
12
--H-m-
12
60
NOTE THE CHROMINANCE REFERENCE AND THE
PROGRAM COLOR BURST HAVE THE SAME PHASE.
30
,SEC
Fig. 1 The new VIR signal waveform is
shown here both as a drawing and the way
it appears on a scope screen, direct from a
VIR generator. TV stations can use it to
correct many video and chroma distortions.
Some General Electric TV receivers now
automatically adjust both tint and color
saturation, when the VIR signal is broadcast.
ELECTRONIC SERVICING
each color program of the ABC,
CBS, NBC, and PBS networks, and
it must remain with that program
until it is broadcast.
This permits the engineers to
make either continuous or occasional adjustments to that individual program, thus maintaining the
original color quality until the program is broadcast.
It is expected that each station
eventually will install equipment
which will make these corrections
automatically and continuously, and
do it so rapidly that the viewers will
not be aware of any manipulation.
In October of 1975, the FCC reserved line 19 of both fields for the
VIR signal. However, the VIR
signal is not mandatory, but optional. VITS now appears on lines
17 and 18 of each interlaced video
field.
Color Quality Today?
ference amplitude are equal at the
output of the R -Y signal in the
receiver, the chroma phase (tint) is
identical to that of the transmitted
reference signal; and
When the chrominance reference amplitude equals the black reference amplitude at the blue -drive
output, the chroma level (color) is
matched to the color saturation of
the original program.
Therefore, the GE VIR system
samples these two signals to determine the correct tint and color
saturation, and adjust it if it's
wrong.
The circuit is not simple; 5 plugin ICs and 30 transistors are used
on the VIR module.
Figure 3 is a block diagram of
the VIR module. Yoú will notice
inputs (in addition to power -supply
voltages) from receiver sync, horizontal -sweep pulses, negative -going
video, R -Y, B -Y, and positive -going
At this time, I see no evidence of Y (video).
any uniformity of color quality that
could be attributed to the use of
VIR Circuits
VIRS, by either networks or staAlthough a defeat switch is protions.
vided for times when the signal is
In addition, TV receiving anten- snowy, or in case you prefer to try
nas and distribution systems often your own color adjustments, the
pulse also is present, the VIR
sensor is turned on for a time
longer than one field. Each repetition of the VIR waveform again
triggers the circuit before the previous one releases control. That way
the VIR sensor remains "on" continuously, even when the VIRS is
received only once each field.
Three outputs come from the
VIR sensor. One works the LED
indicator to show the set is controlled by the VIR. The other two
produce either zero or +28 volts, as
required to switch the tint and
color controllers.
Tint controller
Automatic tint
is
determined by
the relative amplitudes of the VIR
chroma reference and the black reference in the R -Y signal.
From the 63 -microsecond pulse,
generated by the line recognizer,
two other narrower pulses are
made. The 15 -microsecond pulse
provide stronger color on one circuit can switch automatically
channel than on others. This certainly would cause color variations,
even if all station signals were
identical in quality.
General Electric has jumped
ahead of the broadcasting stations
by providing a system of correcting
color saturation and tint errors that
originate in network, transmitter,
receiving antenna, and the color
from manual (no VIR) to automatic
(VIR present), also lighting an LED
to show that the set is controlled by
the VIR.
Line recognizer and VIR sensor
Because the VIR signal appears
only on line 19 (with VITS and
video on the others), the circuit
must accept the waveform of line
receiver.
19 and reject all the others. Line 19
first must be identified, and this is
VIR "Broadcast -Controlled"
done from the receiver sync pulses
Color
by using digital counter techniques.
GE calls this new feature
Next, each line 19 must be
"Broadcast -Controlled" color, and examined for the presence or abit is available in five top -of-the -line sence of the VIR waveform. When
1977 models (some YM and YC-2 line 19 has no VIRS, the horizontal
chassis).
blanking is widened to reach from
All of the VIR circuitry is con- sync pulse to sync pulse. By contained on one seven -inch -square trast, the VIRS waveform does have
module (see Figure 2). A helpful normal horizontal blanking pulses.
service feature is that the receiver One edge of the blanking pulse is
can be operated on manual adjust- used to prove the VIRS is there.
ments, without the VIR module,
After line 19 is identified, the
merely by unplugging the module circuit generates a 63 -microsecond
and connecting together the two (the time of one horizontal line)
plugs from the main chassis.
pulse that coincides with it. From
Mathematical formulas prove this pulse, a 15 -microsecond slice is
these two conditions to be true:
fed to one input of the VIR sensor.
When the chrominance refer- If, during this time the falling edge
ence amplitude and the black re- of the VIR-waveform blanking
July, 1976
Fig. 2 Size of the module containing
the GE VIR "Broadcast -Controlled"
color circuitry is contrasted with one
of the new receivers using it. Digital
readout of switching -type tuners is
another feature.
31
3+5V
DC
SOURCE
POWER
IY0VAC
SUPPLY
28V DC
g OURCE
SUPPLIED FROM
O
CIRCUITRY
./SOURCE
EXISTING
RECEIVER
..f
. d
/ l,
/+22VDC
HORIZ
PULSES
VIDEO
r
l
MA REFERENCE
INTERVAL KEYING
SYNC
111,
LINE
RECOGNIZER
.4.
I>
-Ii.
J L
BLACK REFERENCE
INTERVAL KEYING PULSE
DC SWITCHING VOLTAGES
IL
TO
COUR
LEVEL
AND
TINT
CONTROLLERS
MANUAL OR AU1UMATIC
MODE ACTIVATION)
LINE
19
PULSE -11
Fig. 3 Circuitry Of
the "Broadcast Controlled" color
feature can be
classified into
three areas: line
recognizer and
sensor of the VIR
waveform, plus
switching
voltages for
manual or
automatic
modes; tint
R -Y
B
TINT CONTROL
VOLTAGE
CHROMA
TO
PROCESSINGSCIRCUUITRY
DC
TINT
CONTROLLER
-Y
COLOR
LEVEL
CONTROLLER
+
DC COLOR CONTROL
VOLTAGE
TO RECEIVERS CHROMA
PROCESSING CIRCUITRY
controller; and
color level
controller.
occurs first during the time of the
chroma reference, and the 35 microsecond pulse happens later
during the time the black reference
is there.
These pulses key on two channels
of the comparator circuit, which
judges the relative amplitudes of
the chroma reference versus the
black reference. Output of the
comparator
is a DC voltage
of
approximately +7.4 volts. This
voltage determines the tint setting
of the receiver.
In other words, the signal input
to the "tint controller" is the same
one whose phase is being adjusted
by a DC output voltage from the
controller. It is a closed loop that
continuously restores the optimum
tint.
Color controller
Operation of the "color con-
32
troller" is similar, except the input
signal comes from a combination of
B -Y and positive -going video (together these simulate blue video
drive).
Again, the 15 -microsecond and
35 -microsecond pulses sequentially
extract samples of the chroma re-
ference and the black reference, but
this time from the blue -drive signal.
Output of the comparator is a DC
voltage of approximately +7.4 volts,
which varies until the circuit balances the two signal amplitudes,
producing the correct color saturation.
The color controller also is a
closed loop, that controls the
circuit which supplies the AC input
signal.
Other General Electric Features
All of the picture tubes used in
the new General Electric 1977 line
of modular solid-state color receivers have horizontal in -line guns,
dots of phosphor rather than
stripes, and black -matrix construction. These are said to be the first
25 -inch in -line picture tubes available in the United States. The convergence adjustments have been reduced to 4, compared to the usual
12.
Many YM and YC-2 GE chassis
feature a digital -readout channel
indicator system. combining electronics and mechanics. The digits
are of the glow -discharge type with
a standard 7 -segment display. On
the shaft of the VHF tuner is a 15 -
pole double -throw switch that
switches the display segments for
numbers from 2 through 13. Similarly, the UHF shaft operates a
14 -pole switch. Except for mechanical alignment, these assemblies are
non -repairable.
ELECTRONIC SERVICING
"HOW'S THAT AGAIN?
When you set your clock ahead in the spring for daylight-saving time, do you lose
an hour of
sleep that first night, or do you gain an hour? After many years, people continue
to argue that
puzzle. The same kind of uncertainty sometimes is aroused by hum symptoms or wrong
vertical
and horizontal frequencies. You can troubleshoot TV receivers faster and more accurately
after
you understand the principles illustrated here.
A Rolling Picture
Sweep is too fast
On a TV screen, the picture is
Actually, the vertical sweep is
rolling slowly downward (Figure 1); running fast when the picture drifts
a condition we all have seen many downward. Let's prove that statetimes. Obviously, the frequency of ment.
the vertical sweep is wrong. Is it
When the vertical frequency is
running fast or slow? Of course, fast (above 60 Hz for b -w or 59.94
you could measure the frequency, Hz for color), the scanning beam
but can you prove it by logic?
travels farther down the screen
One wrcng answer
All electronic technicians know
By Gill Grieshaber, CET
that vertical sweep is scanned from the screen. What's more, each
top to bottom. It seems logical, succeeding field also moves the
then, for the picture to be moving picture lower than it was before.
faster than the sweep, thus arriving So, the picture continues to roll
at the bottom of the screen before downward.
the sweep does. According to this
faulty reasoning, the sweep fre- Freerunning frequency
quency is too low. That answer is
Each sweep of the vertical system
wrong! Why? Because the wrong is locked by a separate vertical
sync
reference point was used.
pulse. For best locking, this sync
The picture from the station pulse should arrive slightly before
always must be the standard for the retrace would start if
there were
judging either vertical or horizontal no sync. In other words, the sync
sweep frequencies.
pulses force the vertical oscillator to
fire ahead of the natural time.
Therefore, if the vertical has been
locked correctly, and then the sync
is eliminated, the frequency should
be slightly low (when it runs slower,
the picture rapidly spins upward, as
shown in Figure 2).
A picture that occasionally spins
up is said to have a "vertical flip."
UNDER
Fig. 1 When the picture and blanking
bar move slowly down the TV screen,
is the vertical sweep too slow so the
video moves ahead of it on the way to
the bottom of the screen? Or is the
sweep too fast and moves part way to
the bottom before the blanking bar
arrives?
July, 1976
before it's time for the corresponding part of the picture to arrive.
That moves the picture lower on
Intermittent vertical flip
Have you ever watched a picture
Fig. 2 If the vertical is locked correctly
and then the sync is eliminated, does
the vertical
sweep run faster or
slower? Truth is, the sync should
force the oscillator to fire ahead of
time; therefore, a loss of sync makes
the sweep run slow (flips upward
rapidly).
that had good, solid vertical locking, except periodically would flip
upward several frames, then lock
tine again until the next flip?
Now, this can be caused by variable ghosts. However, the ghosts
will be seen, and that's not the
problem I'm talking about. The
defect I have in mind causes a
41
Tharv'c nne more imnortant
the hum bar always
symptom:
into
it
divide
to
means
(reciprocal
moves. And it moves steadily and
1), or the reciprocal of the time
equals the frequency. That's theory slowly. Any bars of other descriptions might be caused by AGC or
we probably don't use often enough.
horizontal -locking problems. Don't
refor
the
Using a calculator
be deceived; they are not hum bars.
means
Hz
(Hz
of
0.0598
ciprocal
cycles -per -second) gives 16.7224
hum bars move?
seconds. In other words, the 60 -Hz Which way do the
logic. Before,
we'll
try
Again,
will
drift
and 59.9402 -Hz signals
ran faster
sweep
vertical
when
the
in
-phase
becoming
slowly in phase,
than the picture, the picture rolled
every 16.7224 seconds. (Or, out -ofdownward. 60 Hz is faster than
phase once every 16.7224 seconds.)
59.9402 Hz; therefore, the hum bar
By this time, you should undershould drift downward. Right?
flip
vertical
stand the origin of a
Wrong!
approximately
occurs
(not roll) that
True hum bars definitely drift
every 16 or 17 seconds. At one
certain phase, the 60 -Hz hum upward through the picture, when
eliminates the 59.9402 -Hz vertical the picture is locked vertically. This
sync, and without sync the vertical time the vertical frequency (and, of
runs slower (flips upward). Usually, course, the vertical sync, since the
the cancellation of the vertical sync vertical is locked) is the standard,
occurs in the sync separator stage, and the hum is the signal that is
regardless of where the hum ori- changing phase, relative to the
ginates. In rare cases, it might sweep.
happen in the horizontal AFC or
Proof
oscillator stage.
You can prove by two methods
equals the time of one cycle
Fig. 3 A vertical roll that happens
regularly every 16 seconds is caused
by a certain kind of hum.
short period of vertical flip about
every 16 seconds, and does so very
regularly. Figure 3 has a picture of
such a flip. What kind of condition
repeats every 16 seconds?
Vertical versus 60 Hz
During b -w TV
broadcasts, the
vertical scanning frequency is 60
Hz. In other words, there are 60
fields per second, making 30 frames
per second. because of the interlaced scanning requirement.
However, the vertical scanning
rate for color is reduced to 59.9402
Hz, which subtracted from 60 Hz
gives 0.0598 Hz. That's how much
the vertical sweep frequency is reduced for color TV. Of course, the
difference between the two frequencies is only about 0.1%, and it
is of no importance to the vertical
sweep circuit, which will deflect and
lock just as well for either one.
No, the importance of this slight
difference of frequency comes about
because the TV receivers are
powered from the 60 -Hz line.
Therefore, both 59.9402 Hz from
the vertical sweep and 60 Hz or 120
Hz from the ripple of the DC power
supply are present in each TV
receiver.
When the TV is normal, the two
waveforms of nearly the same frequency co -exist peacefully. But
when either has excessive amplitude
(usually it's the 60 -Hz or 120 -Hz
ripple of the power supply), they
can affect one another and cause
trouble.
Let's take a short detour before
stating what kind of symptoms the
trouble between the ripple and
sweep signals can cause.
Time versus frequency
The reciprocal of the frequency
42
Visible symptoms?
Sometimes the hum that eliminates the vertical sync every 16
seconds shows in the picture on the
screen. It might be a large horizontal bar with rounded edges. Or
it might appear as a smaller gray or
black line across the picture. One
bar shows it is 60 Hz, two prove it's
120 Hz.
Fig. 4 A dual -trace scope waveform
clearly shows the slight difference between vertical and power -line frequencies. When the scope is locked to
the vertical (top trace) the heater
waveform (60 Hz) moves slowly to the
left (going upstream of the scope
trace, so it's faster). Also, the hum
moves from the part of the vertical
waveform representing the bottom of
the picture on to the top of the
picture; that's exactly the way visible
hum moves-from bottom to top of
the TV picture.
the statement about hum bars
moving slowly up the picture. First,
you could add hum to the video by
connecting a resistor -substitution
box between a 60 -Hz source (perhaps the heaters of a tube set) and
the video, and varying the resistance to obtain a visible hum bar.
Or, the elegant way is to use a
dual -trace scope, with the top trace
5 Power -supply hum and a
sample of the vertical sweep can be
found together at some point in every
TV receiver. The waveform always
changes in waveshape and amplitude
as the vertical parabola moves slowly
to the right (slower than the 60 -Hz
hum). The scope controls were not
changed between these two pictures,
but the pictures were taken when the
waveform had maximum and minimum
amplitudes.
Fig.
ELECTRONIC SERVICING
Fig. 6 These shaded areas have been
called "silicon -diode radiation", but
that's wrong. Instead, they are modulation bars caused by a change of
signal strength from conduction of the
power -supply diodes. They can't be
seen unless there is a carrier which
can be modulated.
showing a sample of vertical sweep,
and the lower trace with a 60 -Hz
sine wave from the power line
(Figure 4). When the top trace (with
the vertical -sweep waveform) is
locked, the lower waveform slowly
moves to the left.
There are two ways to visualize
the meaning. One is that the sine
wave is going "upstream" so it
must be moving faster. Also, a peak
of the sine wave passes the portion
of the sweep waveform corresponding to the bottom of the picture
(just to the left of each pulse) and
moves slowly to the part representing the top of the picture on the
TV. This proves that hum must
move from bottom to top of an
otherwise normal TV picture.
B
+ waveforms
bola moves slowly to the right
(slower than 60 Hz), with maximum
amplitude (top picture) occurring
just 90 degrees from minimum
amplitude (bottom trace). This is a
kind of poor man's dual trace!
Receivers that have 120 -Hz ripple
show a different waveform. Every
alternate cycle is large, because of
the vertical component added.
These waveforms are normal, but
they pose a question. Where during
this change of waveform do you
measure the ripple? What is the
peak -to -peak ripple?
There is only
one
2 -WAY
RADIO
HOME
STUDY
COURSE
exclusively devoted
to professional FM radio equipment
Other lines
Another kind of horizontal bar is
pictured in Figure 6. Actually, there
are two bars, one at the extreme
top and another near the bottom.
Imagine them drifting slowly toward the top of the picture. They
make a complete revolution every
16 seconds, but are they hum bars?
The answer is both yes and no.
Yes, because their source is the 60 Hz power line. But no, because they
are not true hum bars; instead they
are modulation bars.
Notice the sharp top and bottom
edges, unlike the gradual shading
of hum bars. At the top of each bar
is a lighter area, and a darker
fringe is at the bottom of each.
These edges show AGC action.
The signal is stronger during the
time ofeach bar, so at the bottom
of the bar, a period of several
scanning lines is required to reduce
the AGC voltage. Until the AGC
stabilizes to the new signal condition, the excessive AGC gives reduced contrast. In the same way,
the beginning of the bar (top) has
excessive contrast until the AGC increases to reduce it.
Bars of this kind are not new.
They have been called "silicon diode radiation" or "diode radiation". Tube diodes can cause the
bars, too, but solid-state diodes
make the edges of the bars sharper.
However, these bars are NOT
produced by any mysterious kind of
radiation; instead, they are created
by a change of signal strength. The
signal strength is modulated during
those times. How can a power
supply change signal strength?
Surprisingly, one of the power supply waveforms proves the frequency relationship between hum
and vertical sweep. Figure 5 shows
a double exposure, taken a few
seconds apart, of the waveform
found at the output of the filter
choke in a normal tube -powered
color set. The scope controls were
not changed for the two exposures;
only the waveform changed.
The waveform at that point is a
composite of a near-sinewave of
60 -Hz ripple from the power supply
rectification (this supply doubled
voltage but not the frequency) plus
a parabola (with the points at the
bottom) produced by integration of
the vertical -sweep current (59.9402 Antennas and grounds
Hz).
Most antennas and lead-ins are
As you watch the waveform, it balanced, and then the path bechanges. The notch from the para- tween chassis and an earth ground
We don't know how many
TV repairman or
other people there are
in electronics
who would like to move up to
professional FM two-way radio.
Nor do we know how many
servicemen and installers
there are
already in the field
who want to expand
and upgrade their knowledge.
But we do know how many
home study schools
cater exclusively
to both these groups.
ONE!
Please send me more information.
Name
Address
Code
Li
I
I
C
I
am a former MTI student.
am presently in the military.
am a veteran.
UB
MT/
Formerly
MOTOROLA
TRAINING INSTITUTE
Summerdale, PA 17093
(717) 732-3636
For More Details Circle
July, 1976
(10) on Reply Card
43
supply and power wiring.
Another method, that's employed
by most manufacturers already, is
to connect capacitors across the
power supply diodes. This provides
a constant AC path, so the diode
conduction doesn't make such a
drastic change. In extreme cases,
capacitors might be needed across
the secondary winding of the power
transformer, or from one side of the
the winding of a power trans- AC line to chassis (if that isn't
former), thus changing the resis- already provided). Of course, any
tance of the signal ground. That's such capacitors should be of the
why half-wave rectification causes "fail safe" type.
one shaded bar, and full -wave
circuits produce two shaded bars. Fluorescent -light bars
The signal has been amplitude
Figure 7 shows one example of the
modulated by the changes of ground lines produced by fluorescent lights.
resistance.
There are two main horizontal
narrow bars, having sharp edges
Curing modulation bars
(probably the tube conducts on
used
to
both positive and negative peaks).
Two general methods are
The
bars.
In between these large bars are
modulation
minimize
best one is to use a balanced many narrow ones. They are rather
antenna system, twisting the 300 - faint and difficult to photograph.
Because they are produced by
ohm flat lead-in wire where it runs
from 60 -Hz, the lines drift
current
lead-in
the
or
dressing
TV.
near the
away from the area of the power upward slowly, taking the usual 16
has little to do with signal strength.
But monopole antennas (or dipoles
with the rods unbalanced) require
a ground to complete the signal
path. Of course, it's usually done
by bypassing the AC line to the
chassis, and perhaps we forget how
this acts as a ground.
Diode conduction during rectification temporarily connects B+ to
the hot side of the AC line (or to
Fig. 7 Fluorescent lights also can cause modulation bars. They're seldom seen,
but easy to recognize by the two strong horizontal bars with many weaker,
narrower lines in between.
seconds to return.
Random lines and dots
Random narrow horizontal lines
and dots (Figure 8) are caused by
noise that is not synchronized to
the 60 -Hz line. These were produced by a brush -type motor.
Similar lines and dots can originate
from arcs of the HV system in a
TV receiver.
Lines and dots resembling these,
except bunched in approximate
horizontal bars that drift slowly up
screen, are power -line noise, coming
from arcs and coronas in the power
distribution system.
Hum bars
Figure 9 illustrates two kinds of
hum bars, or rather two parts of
one cycle of hum; dark or light
bars. The shape depends on the
waveshape producing it. A lightly loaded peak -reading power supply
(such as a bias supply) might show
a narrow bar in the shape of a saw tooth (sharper on top than bottom,
or vice versa). And it might be
accompanied by a horizontal bend
of any vertical parts of the picture
(Figure 10).
On the other hand, hum from a
60 -Hz sine wave would have a wide
and rounded bar, either dark or
light.
Of course, all such hum bars
drift up the picture very slowly.
Vertical Lines And
Horizontal Frequency
All vertical lines generated by a
malfunction in a TV receiver must
come from the horizontal -sweep
circuit. There can be one or more,
and they vary in width and position
on the screen. Also, each kind
usually comes from a different
defect.
Several years ago, noise in the
form of vertical bars (Figure 11)
gave a lot of trouble. Usually they
were caused by an obscure defect in
the high -voltage rectifier tube, and
the cure was easy after you knew
this: a new tube stopped the bars.
Today's sets are susceptible to
"jail bars" (Figure 12), a series of
four or five vertical bars, when a
Fig. 8 Noise that isn't synchronous
with either the vertical or the power
line appears at random, without any
pattern. This noise was made by a
brush -type motor.
44
Here are two examples of 60 -Hz
Although the appearance can
in many different forms, two
or dark bars are produced by
120 -Hz hum, and one white or dark
bar is caused by 60 -Hz hum.
Fig. 9
hum.
show
white
horizontal -blanking diode fails.
Barkhausen and snivets were two
other kinds of single vertical lines
that originated in horizontal output
tubes. Modern sets do not have
them.
ELECTRONIC SERVICING
Fig. 10 A hum bar can be white or black; and it can cause an intermittent ver -i cal roll every 16 seconds, a hook in the vertical lines of the picture, or bo h
together.
Fig. 11 Certain kinds of corona In the
high -voltage circuits can emit noise
pulses that form vertical bars.
Fig. 12 Defects in the horizontal blanking circuits (usually bad diodes)
can allow the ringing between pulses
of the high voltage to come through
the video amplifiers, causing vertical
bars.
Out -of -lock bars
All TV technicians and most TV
set owners know that a picture
broken up into diagonal bars
proves the horizontal is not locked.
But, let's be more scientific, and
develop some facts and rules to
help in our troubleshooting.
Look at the picture of a crosshatch pattern in Figure 13, and
assume that the horizontal -blanking
bar shown near the center is
moving slowly to your right. Is the
horizontal -sweep frequency higher
or lower than it should be for
locking?
By using the same logic we did
with the vertical sweep, we find the
frequency must be too high (running too fast). The beam goes from
left to right, and a fast speed brings
the beans past the center before the
video of the blanking bar arrives.
Before this point, the information
had little value, because you seldom
see the condition as described. But,
when we increase the frequency, the
picture changes to the familiar out of -lock stripes (Figure 14).
Now, it's a definite help during
troubleshooting to know whether
the horizontal frequency is too high
or too low. We'll develop a couple
of rules to make it easy to judge
whether it's high or low by the
direction the stripes go.
The scanning beam traces from
left to right, and in Figure 14 the
stripes go downhill from left to
right. All vehicles coast faster
downhill, so we can say: Diagonal
bars going downhill to the right
prove the horizontal frequency is
too high. This applies whether there
is just one bar (from the horizontal blanking bar in the video) or a
dozen.
Of course, bars sloping the other
way show the opposite. Diagonal
bars going uphill to the right
indicate the horizontal frequency is
too low, as shown in Figure 15.
Remarks
Now that we have solved all the
disagreements about the visual effects of hum versus vertical, and
locked versus out -of-lock sweep, do
we gain or lose an hour when Daylight Savings Time begins?
D
ilf,/I/1
/1111111111111111111
1111»I/!i/
1111111l1111111®
11»1111111111111111®
111111111111111111111
////
11111111111111
111/1111//11111
//111111111111
Fig. 13 When the horizontal sweep
runs slightly fast, the picture is moved
to the right on the screen. Diagonal
bars are formed when the frequency is
60 Hz, or more; out of lock.
July, 1976
Fig. 14 When the horizontal -sweep
frequency is too high, the black bars
of the horizontal -blanking bars in the
video slant downhill to the right.
Remember it as a signal going faster
downhill. Each black bar represents a
frequency error of 60 Hz; therefore,
the frequency here is 15,914 Hz.
Fig. 15 Black blanking bars sloping
down to the left prove the sweep
frequency is low. Remember it by a
signal going slower uphill to the right.
One bar is lost in the vertical retrace,
so the frequency is low by 4 bars,
measuring 15,494 Hz.
45
VOLTS
n
M
ANtp
J.J.JJ+
Fig. 1 Starting from the left, these are the Sencore DVM32, DVM38, and DVM35 digital multimeters on our test bench. The DVM36 was not available at that time.
0
I
D
11_
ll
test lab
Each report about an item of
electronic test equipment is
based on examination and
operation of the device in the
ELECTRONIC SERVICING
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.
By Carl
nP,
Babcoke
Sencore Family Of
Digital Multimeters
There are now four models of
digital multimeters in the Sencore
line. It is fair to ask why four are
needed. The pictures in Figure 1
provide part of the answer, although only three of the four are
shown.
Large, heavy, high -accuracy
multimeters (such as the DVM38)
are more appropriate for stationary
operation in the laboratory or on a
workbench. While a light, small
DMM (DVM35, or the higher accuracy DVM36) lends itself for
movable operation at a moments
notice anywhere, powered either by
internal batteries or an external
transformer.
A good compromise between
these extremes would be a mediumsized battery -portable DMM (with
AC option), having most of the
ranges and accuracy of the large
lab model. That niche is filled by
the DVM32.
Of course, these four models
have some family characteristics,
such as automatic polarity on DC,
and more resistance ranges (than
most digitals) with both high -power
and low -power operation.
But unique features also can be
found (special DVM35 probe with
"push -on" and DCV-times-2 readings, or the one-step autoranging
with the DVM38).
Sencore Model DVM35
Smallest of the Sencore digital
meters is the portable DVM35
(Figure 2). A single rotary switch
selects four voltage ranges, four
current ranges, and six resistance
ranges. At the bottom are an on/off
switch, DC/AC switch, and a "zero
adj" control. Readout is by three
LED digits .3 -inch high, and decimal points which are positioned by
ELECTRONIC SERVICING
,M1111!.
Fig.
2
Smallest of the Sencore digitals
is the DVM35, shown in use here.
the range switch.
Digital meters usually overrange
when the input is equal to the
range. That's the case here. For
examFle, with .he 10 -volt DC
range, if you gradually increase the
voltage it reads 7.78, 8.24, and so
on up to 9.99 vclts. Any slightest
increase abose that causes the
meter to overran ge (in this case, the
reading is all 8's, which flash on
and off). Therefore, the maximum
re2dings of the AC and DC voltage
ranges are 999 millivolts, 9.99 volts,
99.9 v alts and 999 volts. (If yoi
prefer to have the low range in
volts, jast imagine a decimal point
in fro -it of the three numbers.
Example: 740 millivolts is .74)
volts.
3 The "puss -on' button of his DVM35 probe extends battery life by
allowing momertary cperation, even when the main switch is off.
Fig.
DC volt3
When checked against the 0.1%
DVM38, this individual DVM35
wa; low in reading by only 0.66% at
Juli,
1976
47
1000
2000
2.
MS
VC
AC
PwR
PWR
AMPS
Oc
AC
3!.o
2000K
200K
2000A
-
Fig. 4 Although the DVM36 appears to be
nearly identical to the DVM35, it has 3-1/2
digits, permitting overranging up to 1999 instead of stopping at 999, and has a basic
accuracy of 0.5% for DC voltages.
better than the
digit.
specs of ±1% of reading
9 -volts DC; which is
fl
Also, it passed the difficult test
of reading accurately with DC
voltages having high ripple or
pulses. Some digital meters, unfortunately, give readings that
change rapidly from too high down
to too low, when measuring halfwave unfiltered DC voltages. One
worst example varied almost 20%.
None of the Sencore digitals had
this problem.
Test probe
Two test leads are attached
permanently to the DVM35, with a
special probe (Figure 3) that has
two buttons. One is labelled
"PUSH ON", and it applies power
to the digital meter when the main
switch is off. This extends the
battery life by reducing the drain to
zero, except during a reading.
The other button has two markings: "ISO" and "DCVX2". Input
resistance of the meter is 15
megohms on all voltage ranges, so
the probe adds a 15-megohm
resistor in series when it is pressed.
This gives isolation to prevent
detuning circuits that are sensitive
to capacitance, and increases the
input resistance to 30 megohms. At
the same time, all DC voltage scales
are doubled (DCVX2), thus permitting readings up to 1999 DC volts.
Caution: don't remove your thumb
from this button when the input
voltage at the probe tip is above
1000 volts; the meter is protected
48
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YW riAKIIR
MIRRY MfAAtEC pRY
20K
ISmA
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Fig. 5 Functions and accuracy of the DVM32 are similar to those of
the DVM36, but there are separate knobs for function and range
selection.
internally only to 1000 volts (total
of DC plus peak AC).
Inside the tip (which screws into
place) is a 2 -ampere fast -blow 3AG
fuse.
AC volts
The same four ranges are used
also for AC voltages, and the input
impedance is the same (15 megohms and 60 pF). Detection of AC
waveforms is average -responding,
and the calibration is RMS.
At 60 Hz, the accuracy is specified at X1.5% of reading E1 digit,
and from 40 Hz to 1 KHz it is
f.5% of reading ±1 digit. This
digital multimeter tested better than
those specs. Response was fairly flat
from 20 Hz to about 1000 Hz, then
rose gradually to about +4 dB at
16 KHz, with a broad peak at 21
KHz and falling response above
that.
Of course, the X2 feature of the
probe is not recommended for AC.
is
important. High -power ohms
have just under 3 volts across the
leads, when they are not connected
to anything.
Lower resistances reduce the
voltage across the leads. For example, a 36 -ohm resistor on the
100 -ohm range measured +.67
volts, while 56 ohms increased it to
+.110 volts. Using the 100K range,
a 5.5K resistor had +.054 across it,
20K had +.207, and 63K produced
+.635 volts.
Power
The DVM35 can be operated on
the six internal AA -size alkaline
cells, or from the power line by
using a PA202 AC -Power adapter.
However, the batteries must be left
in place to act as filters. Or, NiCad
batteries can be substituted, and
the PA202 used as a battery
charger.
Resistance measurements
Model DVM36
In appearance, the DVM36 digital multimeter is nearly identical to
the DVM35 (Figure 4), except for
the switch markings. This model
has 31/2 digits, so the 10 -volt range
goes up to 19.99 before it over ranges; that's why it's called 20
volts here.
Basic accuracy is rated at .5% on
DC volts.
DC voltage at the probes for the
three low -power ohms ranges is
about 1 volt, with infinite resistance
across the leads. The "hot" lead is
positive, for the times when polarity
Sencore Model DVM32
Specifications of the DVM32 are
almost the same as those of the
DVM36; however, the function and
DC and AC
current
Total average sum of AC and DC
is measured, with accuracy of f2%
of reading +1 digit. It's not necessary to change to different input
jacks for current measurements; a
handy feature.
ELECTRONIC SERVICING
9.9 9
r1
mV
OP:tE
-^..-.-
OFf:
VOLTS
OC
AC
»Op A
0.M1
J4
º
OHMS
tt1 PWp
LO
PWR
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ANi4-AAHÓNYO
Fig. 6 Larger size of the DVM32 permits operation from
four "C" cells, thus allowing longer operation before
battery replacement. An adapter is used when line power
operation is desired.
range selections are made with
separate knobs (see Figure 5). Also,
the resistance ranges have separate
high -power and low -power for each
of the six scales. Maximum voltage
with high power is about 4 volts,
compared to approximately .4 volt
for low power.
The larger size permits battery
operation from four
"C"
cells
(Figure 6), with a 39A90 Power
Adapter allowing operation from
line power.
Incidentally, don't use the power
adapter without any internal batteries to act as filters. Before I
bought a set of batteries, I tried the
DMM and found the DC readings
to be about 20% low. Of course, the
operation became normal when the
batteries were installed.
Auto -off
A third
position of the on/off
switch provides a unique feature.
Between measurements, the LED
display digits are blanked out,
saving about 80% of the battery
power. In the sample meter, a reading of 1% or less caused the display
to darken.
AC volts
Input impedance for AC measurements is 1.8 megohm shunted
by 18 pF. Specifications list the
response as 40 Hz to 3 KHz within
+1 dB, but this one was better.
The response was essentially flat
from 20 Hz to about 4 KHz, then
rising slightly to about +3 dB at 15
July, 1976
DVM3B
AMPS
OC
AC
t000 !O ME6.
--- '
"
Fig.
7 Largest Sencore digital multimeter is the DVM38;
it has more ranges (which are pushbutton selected), large
red LED readouts, and single-step auto ranging, a con-
venient feature.
KHz, and rolling off above that
point.
For example, a voltage around +19
might read +19.4, but one around
17 volts would read 17.63.
Probe
A switch in the
200K resistor
isolation.
a
"hot" probe
at
the
adds
tip for
Sencore DVM38
Perhaps the first things you
notice about the DVM38 are the
pushbutton selection of ranges and
functions, and the larger .4 -inch
red LED display digits (Figure 7).
Seven ranges are supplied for resistance measurements, covering 20
ohms to 20 megohms full scale. A
certain resistor checked .03K (30
ohms) on the 20K range, .017 (17
ohms) on the 2K range, 16.8 on the
200 ohm range and 16.76 on the
200 ohm, lowest range. That is ex-
cellent performance.
In addition, high -power and low power ohms voltages are available
for all resistance ranges.
DC voltages up to 1999 can be
measured without extra probes.
When DC volts are being measured, extra LED's at the right of
the 31/2 digits light up "mV" for
millivolts or "V" for volts.
Autoranging
The most unique feature of the
DVM38 is the single-step auto ranging. If you punch in the 200
volt DC buttons, but the voltage is
less than 17 volts, the machine
ranges down to the next scale to
provide better accuracy of reading.
Accuracy
DC voltage ranges always provide
the best accuracy for any meter,
and the DVM38 is rated at f.1%
of reading
digits, with other
functions having slightly lower accuracies. That is very good performance. Response of AC voltages
was down to -1 dB at about 8 KHz,
and -3 dB at 20 KHz, with no
peaks.
Comments
All four of the digital
multi -
meters feature automatic polarity
for DC voltages and currents. The
DVM35 and DVM36 showed "-"
for minus voltages and no symbol
for positive, while DVM32 and
DVM38 showed either "-" or "+".
DVM38 also has automatic zero
function. The other three had "zero
adjust" controls on their front
panels, but none required adjustment during the time of the evalua-
tion.
All digital multimeters provided
final reading very rapidly after
the probes were applied for a
a
measurement. None had excessive
"bobble" of the last digit, and the
DVM38 was outstanding in this
respect.
All models performed very well.
In fact, the only problem you
should have is in deciding which
model is best for you.
49
BE A SHERLOCK OHMS:
by Edmund A. Braun.
1
few minutes to spare? Then have fun solving this Just -across -word puzzle
Electronics. Each word is connected to the word above and below by one
on
based
or more letters although only one is usually shown as a clue. Each correct answer
is worth 4 points; a perfect score is 100. It shouldn't be difficult to get a high
rating except perhaps for someone who is sure "scrambler" its for preparing eggs,
2
tumbler who performs gymnastics! Ready? Then
4
Have
a
or that "achromatic" refers to
start deducing!
a
3
Intimately fused mixture of
two or more metals.
In an oscillator, the
undesired change from a
desired frequency.
Vary irregularly; to rise and
fall.
Antenna characteristic
5
6
7
L
8
9
C
10
i
11
L
E
o
bronze.
o
15 Not having
stored in a
0
battery.
G
18
16
19
T
R
i
1
20
19
20
tube that
provides push-pull
amplification with a single
tube.
An alkaline metal having
photosensitive characteristics
especially in blue light.
Two triodes in same tube
envelope.
Pertaining to a plug that may
be inserted in receptacle in
only a predetermined
position.
A combination of
components which, when
inserted in a circuit, change
the frequency response of
the device.
21
2
22
23
T
24
24
25
25
50
electrical energy
capacitor or
16 Five -electrode
17
17
Vacuum tube whose
electrical properties are
modified by action of light.
12 A transformer's output
winding.
13 The initial transient response
to a unidirectional change in
output.
14 A coating that forms like
rust on brass, copper, or
N
1
determining orientation.
Immeasurably small;
approaching zero.
The servicing, repair,
overhaul, and upkeep of
equipment.
Having an output that
doesn't vary in direct
proportion to the input.
The suitability of a subject
or model for televising.
Quality of being sharply or
exactly defined. Accuracy.
Centimeter -gram -second
electromagnetic unit of
electrical quantity.
A
EDMUND_ A, BRAUN;:;;
Pertaining to a current which
varies periodically but
doesn't reverse itself.
An electrode of a transistor.
A cgs electrostatic unit of
charge.
Cathode-ray tube with screen
composed of halide of
sodium or potassium.
Type of coil named for an
Austrian -born American
electrician and inventor.
We know you wouldn't sneak a
peek so we'll tell you frankly
the solution is on page 54.
SERVICE ASSOCIATION
CONVENTIONS
NATESA
National Alliance of Television & Electronic Service
Associations (NATESA) has chosen August 19th through
22nd at the Pheasant Run Lodge in St. Charles, Illinois (a
suburb of Chicago) for its 1976 convention.
Convention activities include: official business meetings; meals; banquets; floor show; and many other
features, including messages from leaders of the
electronics industry. A full -participation ticket for the
convention is $25.
NESDA
During August 13th through the 17th, the annual
conventions of the National Electronic Service Dealers
Association (NESDA), International Society of Certified
Electronic Technicians (ISCET), and Texas Electronic
Association (TEA) will be held simultaneously in San
Antonio, Texas. A partial listing of convention events is
as follows:
Friday,
August 13
Open Golf Tournament
TEA Meeting
Welcome To Texas
For more details, contact:
NATESA
5908 South Troy Street
Chicago, Illinois 60629
Saturday,
August 14
Keynote Breakfast
(Sponsored by GTE Sylvania)
Speaker is Toby Mack, EIA
ISCET Meeting And Election
Mercado Electronica '76 (Trade Show)
Refreshments by Raytheon
RCA Luncheon
Howard W. Sams Cocktail Party
Zenith Banquet
3513
Sunday,
HITACHI
August 15
ISCET Breakfast
Manufacturer Panel Discussions
Technical And Business Seminars
Sony Luncheon
Sony video -disc demonstration
NESDA Officer Nominations
P-04, P-05
1577-1
J C PENNEY
28778, 685-2877B (855-1996)
1585-1
VhOtOItCtI.
ADMIRAL
Chassis 4M10D35-1
1591-1
BROADMOOR
K
1591-2
MART
SK9B617/M,
SK12B618/M
1583-1
Monday,
August
16
Panasonic Breakfast
NESDA Annual Meeting and
election of officers
Magnavox Luncheon
Hall Of Fame Banquet
Don Martin, Master of Ceremonies
Tuesday,
August 17
Executive Council Planning Meeting
Profitable Service Management School
Ladies Business Seminar
RCA
Chassis CTC81 B
Chassis CRK22A/DAP-1
1589-1
1589-A
SANYO
91T51
1590-1
SEARS
562.40092500
1590-2
SHARP
3M-46
1588-2
SONY
Convention registration fee is $40 per person, exclusive of
fees for optional events, such as Business Management
Schools, Texas barbeque, Air Museum tour, and the golf
tournament. San Antonio is a historic city with many
opportunities for sightseeing.
For more details, contact:
NESDA
1715 Expo Lane
Indianapolis, Ind. 46224
Phone: 317/241-8160
July, 1976
Chassis SCC-64B-D/-64B-E
Remote Control RM -301
1592-1
1592-1-A
SYLVANIA
Chassis E21-3/-6
1587-1
TOSHIBA
Chassis TAC -550
1592-2
TRUETONE
G EC3713A-77 / 15A-77
1589-2
5'
CB Repair Kits
Two kits for repairing CB and
vroductup
scanner radios are available from
General Electric. The solid-state kits
supplement GE's basic K-935 kit
introduced last fall for repair of CB
and other Far -East -built consumer
electronics.
Kit K-936 provides 16 types with a
quantity of 37 items. Kit K-937 has 16
types with a total of 36 devices. Parts
for each kit are filed in a 24 -drawer
storage cabinet with pull-out drawers.
All drawers are interchangeable.
The kits are complete with a special
12 -page cross reference parts guide
(ETRO-7622) keyed to the brand of
equipment to be repaired.
These features supp ied by the
manufacturers are listed at no -charge
to them as a service to our readers.
If you want factory bulletins, circle the
corresponding number on the Reply
Card and mail it to us.
CB Converter
"Signal 23" from Finney Company
is a CB converter for auto installation.
It converts all 23 CB channels to the
standard AM broadcast frequencies.
For More Details Circle
(28) on Reply Card
The new solder, called Savbit, is a
Antenna Alarm
copper -loaded, tin/lead alloy wire
accessory from The MagiA
new
rosin
of
cores
with
separate
5
solder
base flux. Test results show it tran Company, called the Antenna
reduces the solution of copper by as Anti -Theft Alarm Activator, activates
much as 100 times.
The converter uses the auto radio's
antenna, eliminating the need for a
special antenna.
"Signal 23" has a gain control, a
crystal -controlled oscillator, and incorporates an RF stage. It uses a
FET to provide sensitivity of less
than 1 microvolt at 10 dB SN ratio. A
dual -gate MOSFET mixer minimizes
cross modulation.
The converter takes only a few
minutes to install and comes complete
with all hardware, instructions, and a
limited consumer warranty. It has a
list price of $38.00.
For More Details Circle
(24)
on Reply Card
Savbit is recommended for applications where copper soldering tips
are used, because it prevents rapid
pitting and wear.
For More Details Circle
(26) on Reply Card
CB Transceiver
The Sparkomatic Corporation now
marketing a 23 -channel CB transceiver.
Model CB -1123 has an easy -to -read
illuminated channel selector, transmit
modulation light, volume control/onoff power switch, illuminated signalis
a car horn or auto alarm system when
a protected antenna is lifted from its
base. The CB 10-57 will work with
any auto -alarm system, car horn, or
for extended range, an external
trumpet or siren. It is compact and
strength and radio-frequency output
meter, variable squelch control, automatic noise limiter switch, and comes
with chrome mounting bracket and
hardware.
The CB -1123 also includes a public
address switch, jacks for P.A. speaker
and external speaker and a screw down type detachable microphone.
CB Installation Kits
Two CB auto -stereo installation kits
now are available from Littelfuse.
The kits contain everything necessary to install a CB radio or auto
stereo: fuses, wire connectors, tab
terminals, quick -connect terminals,
and in -line fuseholders. Each kit also
contains quick -release set disconnectors, which allow the unit to be
removed from the vehicle.
The kits are available in a "single pack" version, containing everything
needed for one installation, and in a
"six-pack" for six complete installations. Each kit has easy -to-follow instructions.
For More Details Circle
(25) on Reply Card
Savbit Solder
Multicore Solders has developed a
solder specifically to prevent the
dissolving of fine gauge copper wires
and thin copper foils during soldering.
52
For More Details Circle
(27) on Reply Card
ELECTRONIC SERVICING
CASTLE
easily concealed; it can be used with
all grounded antennas having a base
loading coil, and is powered by the
vehicle's regular battery.
For added protection, the CB 10-57
comes with an antenna retention
strap that keeps the antenna attached
to the vehicle even after it has been
unscrewed.
CFNSITIVITY
Microwave Oven Control
Litton's variable power control
... for the Professional
is
now offered on its two new Micro matie Model 900 double -oven micro-
SU88ER'
wave ranges.
The Vari -Cook oven control allows
the homemaker to change microwave
cooking speeds for different foods. By
varying the power from 65 to 650
watts, she can get the slow -cooked
flavors of a stew or gourmet sauce,
but at microwave speeds. The selfcleaning lower ovens on both units
are also the first to feature a new seethrough door without a heat shield.
For More Details Circle
Timesavers
Mark
signa/ circuit analyzing
Instruments
V
(30) on Reply Card
ECG Semiconductors
Mag-#e
ANTITHEFT
A new GTE Sylvania kit provides
ENNA
replacements for semiconductors most
often subject to failure in CB radios.
The kit includes 23 transistors and
three integrated circuits for replacing
drivers, modulators, RF outputs and
other semiconductors. The devices are
available in rack or carton pack.
ALARM ACTIVATOR
MODEL CB10 57
OFF
For More Details Circle
(31) on Reply Card
Pocket -Size Data Guide
This 3-1/2"
For
More Details Circle (29) on Reply Card
"It isn't how much
you give
that counts,
it's the spirit:'
X 8-1/2" slide -rule Data
Guide contains up-to-date material
from recognized standards that is
useful in everyday technical applications. It contains data such as impedance formulas for series and
parallel circuits, copper -wire tables,
conductor and insulator properties,
DB tables, current, power formulas,
AC and DC circuits, resistor color
codes, metric conversions, common
conversions, etc.
Ask your electronic distributor for them
.. or write for more details.
Baloney.
CASTLE ELECTRONICS, INC.
Too many people make a token
contribution to the United Way
Campaign, and sit back and figure
they've done all they should.
They haven't. A token contribution
isn't enough. Our community
doesn't have token problems. If
you really care, if you really want
to help solve our problems, you'll
give more than a token. You'll give
your Fair Share.
5701
Western Ave., Chicago,
Ph
60645
Finkler Ltd., Ontario
For More Details Circle
(11) on Reply Card
APPLIANCE REPAIR BOOKS
Written in easy -to -understand language by experts with illus.
trations 8 diagrams Acclaimed by instructors g p'olessionals How to diagnose 6 repart au conditioners refrigerators.
vacuum cleaners ranges. washers. dryers. steam irons portable kitchen appliances. wafer healers; plus how to set up a
shop, using lest instruments and more. Only $2.65 lo $4.90
each!
SEND FOR FREE DESCRIPTIVE PRICE LIST
C
& N, DEPT. ES,
5841 MONTROSE, CHICAGO 60634
For More Details Circle
(12) on Reply Card
FREE ALARM CATALOG
is to do.
If you don't do it, it won't get done.
io
cod
Price of the Data Guide is $2.95 pp,
and it is available from Technical Aid
Corporation.
For More Details Circle
(32) on Reply Card
Huge
tems,
frared
bells,
selection of burglar & fire syssupplies. Motion detectors, inbeams; controls, door switches,
sirens. 500 items, 99 pp. packed
with technical details, notes.
(Outside U.S., send $1.00.)
0
mountain west alarm
4215 n. 16th st., phoenix,
For More
July, 1976
III.
[312] 728-1800
In Canada: Len
You'll realize why the spirit of
giving just isn't enough anymore.
And you'll probably know, and
care about, how much there
advertising contributed for the public good
N.
az. 85016
befalls Circle (13) on Reply Card
53
test equipment
-'1[PCJYil
These eatu es supplied by the
manufacturers are listed at no -charge
to them as a service fo our readers.
If you want factory bulletins, circle the
corresponding number on the Reply
Card and mail it -to us.
Portable DMM
Model 6000 is a portable digital
multimeter from Weston Instruments.
Automatic ranging is provided for the
five standard measurement functions:
AC volts, DC volts, AC amps, DC
amps and resistance. Twenty-six dif-
ferent ranges cover voltage measurements from 200 mV to 1 kV, current
measurements from 2 mA to 10 amps,
and resistance from 200 ohms to 20
megohms. A "Hold" input jack provides memory -retention for remote
measurements. Automatic zero and
automatic polarity are built-in.
Basic accuracy of Model 6000 is
0.35%; resolution of the voltage
ranges is 100 microvolts, and 0.1 ohm
for resistance.
It has a 0.5" high Liquid -Crystal
Display (LCD), with large black
digits that can be seen easily. Alternate blinking of the display indicates
over -range.
The Model 6000 is powered by two
9 -volt transistor batteries. Typical battery life under normal instrument
operation is approximately 200 hours.
Model 6000 sells for $195.
For More Details Circle
(15) on Reply Card
CB Test/Power Meters
Eico has a complete assortment of
test equipment for CB's. The 715
"Transmatch" measures: RF power to
50 watts; standing wave ratio; both
forward and reflected power; and
modulation percentage. It features a
built-in 50 -ohm dummy load. The 715
sells for $69.95.
The 725 SWR/Power meter connects between the transceiver and the
feedline to the antenna, thus causing
minimal insertion loss. The dual -range
wattmeter selects either 0-10 or 0-100
watts, and has a broadband frequency
response of 3 MHz to 144 MHz. The
725 is priced at $39.95.
Eico 735 is a 1000 watt, inline
power -output meter for 50 -ohm lines.
It absorbs negligible power when in
use, and will continuously monitor
powers up to 1000 watts. Three
ranges expand the meter from 0-10
54
watts, 0-100 watts and 0-1000 watts.
The frequency range is 3 MHz to 150
MHz. It is priced at $29.95.
The 745 SWR/Field-Strength Meter
connects into the circuit and continuously monitors standing wave
ratio, relative forward -and -reflected
power, and field strength. It is capable of measuring standing wave
ratios of 3:1 or higher, and sells for
$19.95.
The 755 Mini Mobile Field -Strength
Meter monitors both antenna and
transceiver operation and performance. It does not need tuning or
attachment to any part of the transceiver; frequency range is 2 to 200
MHz. The 755 is priced at $9.95.
For More Details Circle
31/2 -Digit
(17)
on Reply Card
Multimeter
The Model 283, a new 31/2 -digit
multimeter priced at $170, has been
announced by B&K-Precision.
Model 283 has high -intensity LED
displays, 0.41" high, that can be read
easily in brightly -lit rooms at a
distance of at least six feet, according
to the manufacturer. It measures DC
volts, AC volts, DC current, AC
current and resistance, with 100%
overrange. Out -of -range is indicated
by a flashing digit and three zeros.
All readings have an automatically positioned decimal point.
Model 283 has 4 DC voltage ranges,
with X0.5% accuracy on the 1.000,
10.00 and 100.0 ranges and X1.0% on
the 1000V range. Polarity indication is
automatic. Four AC voltage ranges
have ±1.0% accuracy on 1.000, 10.00
and 100.0 ranges and 1.5% accuracy
on the 1000V range. There are four
AC current and four DC current
ranges, with the similar accuracies.
The six resistance ranges, 100 ohms,
1k, 10k, 100k, 1000k and 10 megohms,
have .10/o accuracy, except for the
top range which is -±2%. Input impedance is 10 megohms on all voltage
ranges.
For More Details Circle
(16) on Reply Card
±2%. The generator has built-in
modulation plus a crystal -controlled
oscillator circuit. Included is a twostep ten -to -one switch plus vernier for
VFO sweep -output attenuation and
a two -position seven -to -one switch for
crystal oscillator attenuation. Suggested price is $117.
The signal generator is one of
several new products announced since
VIZ acquired the RCA test -instruments business.
For More Details Circle
RF Wattmeter
Coaxial Dynamics has a
It covers fundamental frequencies
from 85 KHz to 40 MHz in six ranges,
and harmonic frequencies on higher
bands. The selection switch has two
positions for special 455 KHz and 107
MHz sweep outputs for broadcast and
FM IF sweep alignment. The RF output is 75 millivolts or more for all
ranges; dial calibration accuracy is
4 -range
termination -type wattmeter that
covers 20 to 512 MHz and services
everything from hand-held portable
transmitters to base -station installations. The most -sensitive power range
measures three watts full scale.
Model 85 is designed for use in 50 ohm coaxial systems as an accurate
direct -reading RF wattmeter, and a
150 -watt non -radiating dry termination load.
For More Details Circle
(19) on Reply Card
For Faster
Action
Use Our
Reader Service
Cards
Solution to:
BE A SHERLOCK OHMS
1
2
3
4
5
6
7
8
9
10
11
12
13
RF Signal Generator
VIZ Test Instruments Group offers
a new solid-state radio signal generator called the VIZ WR -50C.
(18) on Reply Card
alloy
pulling
fluctuate
14
15
directivity
infinitesimal
17
18
19
verdigris
uncharged
16 pentatron
maintenance
nonlinear
telegenic
precision
abcoulomb
photocell
secondary
precursor
20
21
22
23
24
25
potassium
duotriode
polarized
equalizer
pulsating
collector
stathenry
draktrace
Tesla'
l'Nikola Tesla (1856-1943) designed
power system at Niagara.)
Start with 100 points and deduct 4
points for any part you may not have
answered correctly.
Your rating:
60-64 Fair.
68 - 72 Pretty good.
76 - 84 Very good.
88 - 96 Excellent.
100 PERFECT/
Congratulations, Sherlock Ohms!
ELECTRONIC SERVICING
audio sVstems
jijptI
These eatu es supplied by the
manufacturers are listed at no -charge
to them as a service to our readers.
If you want factory bulletins, circle the
corresponding number on the Reply
Card and mail it to us.
The 4 -ohm speakers have a
sponse from 100 Hz to 16,000 Hz,
are rated at 10 watts RMS. They
compatible with any radio used
reand
/
NEW from JERROLD
are
teN\
se
for
moving vehicles. Suggested resale
price is $24.95 for black or cream
finish, and $29.95 for chrome.
For More Details Circle
(20) on Reply Card
Tape-Player/Radio
universal 8 -track player and AM
FM stereo receiver has been introduced by Audiovox Corporation.
Model ID -400 is a compact, solidstate sound center with the following
features: AM -FM slide -bar selector,
FM local -distant reception switch,
tape program indicator lights, and
flip -away dial scale/tape-cartridge
door. Power output is 7 watts per
channel; for 12 -volts negative ground.
No additional kits are needed for installation; all necessary parts are included in the package, with photographic instruction guide. Suggested
retail price is $145.50.
A
Motorcycle Speakers
Neosonic Corporation has available
Sonosphere SPR-12 speakers for use
on motorcycles.
The SPR-12 speakers mount directly
onto the sides of the ignition -switch
console, and can be swiveled up or
down and side -to -side to provide the
most effective position for sound
direction. The entire installation protrudes approximately 5" from the surface. Speakers are sealed in 43/4" diameter steel spheres that are rear damped with fiberglass to eliminate
the back wave.
r----your subscription to
Electronic Servicing,
15
)
AFFIX
LABEL
HERE
Change of
Address
If you're about to
move, please let us
know approximately
barrier strips
with captivated screws for direct
connection to speaker wires. Suggested net price is $31.50.
For More Details Circle
(22) on Reply Card
Extension Speaker
about.
Simply affix
your present label
here, and carefully
print the updated Information below.
Please Help Us to Serve You Better
Electronic Servicing
1014 Wyandotte Street
Kansas City, Mo. 64105
Name
(Please Print)
Employer
Address
State
KHz.
Model A102A has
Components Specialties offers
four weeks before
the move comes
City
POWER MATE
MAST MOUNTED
PREAMPLIFIERS
(21) on Reply Card
Four power taps (50, 25, 12 and 6
watts) are provided for connection to
the 70 -volt speaker line from the
power amplifier. Power rating is 50
watts; frequency response is 50 Hz to
Anytime you have
a
question about
r
For More Details Circle
PREAMPS
70 -Volt Transformer
Model A102A is a weatherproof,
low -loss, 70 -volt line -matching autotransformer from Shure Brothers.
Help!
please include a
mailing label to insure prompt service
on your inquiry.
-
Zip
an
extension speaker designed specifically for the CB audio response of 700
to 2,000 Hz.
SPECO Model CBS -4 comes with a
miniature plug on the end of its 10 foot cable for connection to most CB
base stations. Also included is a PL -55
adapter plug in the event the base station has a standard -type jack. The 4"
speaker has a heavy ceramic magnet
and provides 5 watts of nominal
power. Impedance is 8 ohms or lower.
Made of ABS, Model CBS -4 is heat resistant and weatherproof. It has an
adjustable, metal mounting -bracket
that locks into any position. Suggested resale price is $14.95.
For More Details Circle
(23) on Reply Card
COLDRCASTER
INDOOR
AMPLIFIERS
Xtra
Xtra
Vitra
output capability
low noise figure
FM rejection
For many years, Jerrold Powermate
and Colorcaster TV antenna signal
preamplifiers have been the standard of
the industry.
Now, they are even better, providing
higher output capability (6 to 10dB in the
VHF range) lower noise figure and greater FM rejection. Special attention has
been given to the higher UHF channels
so that in translator areas, the
preamplifiers do an excellent job.
Jerrold preamplifiers with X -tra High
output capability, X-tra low noise figure
with X -tra FM rejection provide an
overload -free superior performing product.
JERROLD El
a GENERAL
INSTRUMENT company
Distributor Sales Division
Horsham, Pa.19044 e (215) 674-4800
July, 1976
For More Details Circle
(14) on Reply Card
The MARKETPLACE
This classified section is available to
electronic technicians and owners or
managers of service shops who have for
sale surplus supplies and equipment or
who are seeking employment or recruiting
employees.
Advertising rates in the Classified Section are 35 cents per
word, each insertion, and must
be accompanied by cash to
insure publication.
Each
counts
initial or abbreviation
a
full word.
BUSINESS OPPORTUNITY
TRANSISTOR TESTER. Convert transistor radio
into in -circuit transistor tester. Tone indicates
good transistor. Plans $2.00. SZA Electronic Systems Inc., 39 Bayberry La., Levittown, NY 11756.
7-76-3t
CONVERT black/white TV to color: experience
not necessary. $3.00 (refundable). Tayo Paul, 980
5-76-3t
Greene Ave., Brooklyn, N.Y. 11221.
PICTURE TUBE MACHINE -We buy and sell
NEW and USED CRT rebuilding machinery.
COMPLETE TRAINING. Buy with CONFICENCE
from the ORIGINAL MFGR. For complete details,
sen name, address and zip code to: LAKESIDE
INDUSTRIES, 3520 W. Fullerton Ave., Chicago,
7-76-1t
Ill. 60647, Phone: 312-342-3399.
EASY -DOES -IT -One-Man TV Cart! Will tote a
color TV stereo 6' long. The answer to the oneman shop or the high cost of sending two men to
do it! Box 296, Mt. Pleasant, Utah, 84647 for
7-76-1
information.
132 ASSORTED TV -Tubes.
For ads on which replies are
sent ta 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.
not open
products
manufacand no
manufac-
t
Price $100.00. Call
7-76-1 t
215-WA7-2938.
Minimum classified charge $3.00.
Classified columns are
to advertising of any
regularly produced by
turers unless used
longer owned by the
turer or a distributor.
FOR SALE (CONT.)
GET LATE MODEL Color N's (rebuildable) for
$10-$20-$30. All you can use. Practical plan
makes to $100 day plus for skilled TV Techs. Detailed instructions, method, $10 ppd. Economy TV
7-76-2t
Rentals, Box 2890, Denver, CO 80201.
SAMS TV PHOTOFACTS-57 thru 1334 of most
popular models, about 400 folders. Best offer.
Calais Repair Service, 2819 E. Smicoe St.,
7-76-1 t
Lafayette, La., 70501.
NEW Canadian Magazine "Electronics Work
shop". $5.00 yearly. Sample $1.00. Ethko, Box
10-75-12t
741, Montreal A" Canada.
CONVERT any transistorized T.V. tuner to a tuner
substituter. Plans $2.00. New accelerated Radio
& T.V. course. RADIO TELEVISION TRAINING,
8-75-tf
Box 279. ES -66, Syracuse, N.Y. 13206.
STOP...don't junk that television set. ASE manufacturers the world's most complete line of television picture tubes. No other company offers:
Over 1700 types of television picture tubes. Most
types immediate delivery. Transportation in the
Midwest -paid, 1/2 transportation paid in other
states. Tubes for Old or New Models. Complete
line of both black & white and color. Full 2 year
factory warranty. Lowest prices anywhere. Finest
quality. Write today for more information. Allied
Sales & Engineering, Inc., Dept. 27, Pimento,
6-76-21
Ind. 47866, Telephone - 812-495-6555.
TV SALES/SERVICE BUSINESS. Southern British
Columbia, Canada. Store built 1967 has two
levels, 960 square feet each level on 1/2 acrealand
on main road. Three major brands. Close to
resort area, hunting, fishing. Gross 1975 $78,000
and growing. $100,000 plus stock. Dept. 509,
6-76-3t
1014 Wyandotte, K.C., Mo. 64105.
TV SERVICE BUSINESS in small mountain
community. Operating for 10 yrs. Retiring. Gross
$15,000 only part time. Only service in 30 mile
radius. Expansion potential unlimited. $15,000
includes 74 van. R. Murray; Box 816; Hayfork,
6-76-2t
Calif. 96041.
REJUVENATE TELEVISION PICTURE TUBES
without equipment. Use power from TV. Send
Tube Number and $5.00 to: W. R. Collins, Jr.,
7-76-1t
HHC, 4TC, BDEPPD, APO N.Y., 09451.
JERROLD MODEL 890 sweep frequency generator. Range 25 mHz to 1000 mHz. $450. Videon TV
7-76-1t
1-717-564-4566.
56
ESTABLISHED TV SERVICE shop in beautiful
Piedmont Section of North Carolina. Excellent
opportunity at reasonable price. Write E. M.
Brown, 313 Linville Springs Rd., Kernersville,
7-76-1t
NC 27284.
21 year old TV repair
business, large store with attached 6 room
house, 50' basement, 50' attic, separate paneled
20' x 20' garage with heat & electric. Entire
property approximately 60' x 135'. All Zoned
business. Located in lovely residential area, Well
equipped shop, all electronic instruments. House,
furnished or unfurnished. Retiring & moving
South. Asking $48,000. Bellmore, Long Island,
FOR SALE -Established
7-76-1 t
New York. 516-785-9127.
location 15 years.
Nets over $25.000. Retiring. Including truck,
equipment & inventory $25,000. A. Bolin, 6361
6-76-tf
Balsam Lake, San Diego, Ca. 92119.
TV SALES & SERVICE in same
SELLING SUPREME PUBLICATIONS' manuals to
50% discount. Beitman, 1760 Balsam, Highland
7-76-1t
Park, IL. 60035.
SONY REPLACEMENT PARTS, For Color Televi-
sions. Tuners, filament transformers, audio transformers, antennas, handles, etc. All items new,
and priced far below Sony replacement cost
Volume discounts. Inquire: 22525 Kingston Lane,
Auburn, CA, 95603. Phone (916) 272-1971. 7-76-1t
ARIES -50 mHz frequency counter $110. H.
Geller, 12622 NE 3rd, Bellevue, Washington,
7-76-1t
98005.
FOR SALE
TV SHOPS -Increase your income. Repair and
update MATV systems with patented method.
$200.00 day possible. Training available. P.O.
7-76-6t
Box 809, Boynton Beach, Fla. 33435.
UNUSUAL SURPLUS AND PARTS Catalog. $1.
ETCO Electronics, Dept. E.S., Box 741, Montreal
7-76-10t
"A" H3C 2V2.
SOLID STATE &
HOBBY CIRCUITS MANUAL
$1.95 postpaid to your door. The new
manual offers over 400 pages of circuits for the hobbyist, engineer, experimenter and do-it-yourself kit builder. HURRY -Supply limited. Free catalog. Frazer & Associates, Dept. ES,
1888 Century Park East Suite 10, Century City, Calif. 90067.
WANTED
PICTURE TUBE REBUILD PLANT complete. Cost
between $1500.00 & $2500.00. Vern Fisher, 388 E.
6-76-2t
300 N. #18, Springville, Utah, 84663.
WANTED -One used Telequipment Oscilloscope
TL-D61. B & A Radio-N, 30 Oak, Hogansville,
7-76-1t
Georgia, 30230
EDUCATION -INSTRUCTION
REPAIR TV TUNERS -High Earnings; Complete
Course Details, 12 Repair Tricks, Many Plans,
Two Lessons, all for $2. Refundable. Frank
Bocek, Box 3236 Enterprise, Redding, Calif.
4-76-4t
96001.
TV PROBLEMS'??? Send symptoms with a copy
of schematic and self-addressed stamped envelope and $2.00, to Troubleshooter, Box 4553,
iowney, Ca. 90241. Results Guaranteed. 9.75-íf
advertisers' ºIY
º;;.
American Technology
2
Corporation
B & K Div.,
Cover 3
Dynascan Corp.
Bussman Mfg. Div.,
Cover 4
McGraw -Edison
53
Castle Electronics, Inc.
53
Charous & Niebergall
11
Chemtronics, Inc.
Cleveland Institute of
33
Electronics
11
Dana Laboratories, Inc.
10
GC Electronics
9
Gem City Tuner
35
Heath Company
Jerrold Electronics
55
Corporation
43
MTI
Mountain West Alarm
53
Supply Co.
35
Pomona Electronics
Precision Tuner
Service ....Cover 2, 1, 33, 35
33
Prentice -Hall, Inc
26, 27
RCA
Sperry Tech, Inc
GTE Sylvania -ECG Consumer Renewal
Tuner Service Corporation
Winegard
2
3
5
7
ELECTRONIC SERVICING
rp4KPRECIS/ON
...you'll want it for its features
...but it's the price that will sell you!
High intensity LED display is easily read from
at least 6 feet in the brightest room
0.5% DC accuracy
100% overrange (1000 scale reads to 1999)
Automatic polarity
Automatic decimal poi it
Flashing overrange inc ication on display
Four ranges each for voltage and current
Six resistance ranges lo 10 meg.
Reliable In -circuit resistance measurements
Overload protection on all ranges
Complete new circuitry Hakes the Model 283 the
most dependable and versatile 31/2 digit
multimeter you can buy. The extra -bright display
allows you to use it where other units would
cause reading problems. The selectable "low
ohms" function permits accurate measurement
of semiconductor shunted resistors.
For More Details Circle
An optional, internal battery pack (BP -83,
$50.00) provides 8 hours of continuous use on
one overnight charging and charges when
the Model 283 is in use on 115/230VAC.
Thoughtful, convenience features like a side
carrying handle, tilt stand and detachable line
cord add to its usefulness.
Your B&K-PRECISION distributor has them in
stock and will be glad to demonstrate its features
to you. Call him, or write for additional
information.
OK PRECISION
PRODUCTS OF DYNASCAN
6460 West Cortland Avenue
Chicago, Illinois 60635 312/889-9087
In Canada: Atlas
(2) on Reply Card
Electronics, Toronto
Buss® Fuses
Specialize
Too!
in the protection of
EQUIPMENT
four new BUSS fuse assortments
Now
exclusively designed with replacement fuses to
service most Citizen Band Radios
offering a
whole new area of opportunities for increased
profits.
Two assortments contain 48
5 in metal boxes
(240 fuses). BUSS No. 240CB-3 fuse assortment
comes in a handy metal display stand. BUSS No.
240CB-4 fuse assortment is packed in a compact
plastic display box.
In addition, there are two fuse assortments containing 16
5 in metal boxes (80 fuses). BUSS
No. 80CB-1 fuse assortment packed in a metal
display stand and BUSS No. 80CB-2 fuse assortment in a plastic display box.
Both BUSS fuse assortments contain a careful
selection of the most popular fuses used in CB
radios.
CB dealers can now have the fuses they need in
a neat complete package to service all their
customers fuse needs.
For full fuse assortment details, write for BUSS
Bulletin CBA.
.
.
.
-
-
-
No. 240CB-3
No. 80CB-1
Metal Display Stand
Metal Display Stand
No. 240CB-4
Plastic Display Box
No. 80CB-2
Ca]
Plastic Display Box
BUSSMANN MANUFACTURING
McGraw -Edison Company Division
St. Louis, Missouri 83107
a
FUSES
THE QUALITY UNE
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