Ele"CvIiroh)(12Ìlc - American Radio History

Ele"CvIiroh)(12Ìlc - American Radio History
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IS 1J392139 608
November, 1976
-13f1bJNS
Ele"CvIiroh)(12Ìlc
75 cents
I
REPAIRING "WIRELESS" CB RADIOS
GE And Philco Circuits
www.americanradiohistory.com
Upgrading MAW
/
From the beginning,
our goal has been to
provide the best tuner
standards of excellence we apply to every
job. 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
reliability and the
ORIGINAL PARTS
ONE YEAR WARRANTY
COLOR, BLACK & WHITE, TUBE,
TRANSISTOR OR VARACTOR . . . ANY MAKE OR MODEL.
WE REPAIR THEM ALL
VHF or UHF.
.
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.$10.95
UV -Comb.
(MAJOR PARTS AND SHIPPING EXTRA
...
e.. .
OMM
S
-
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.
.$17.95
DEALER NET)
PTS ELECTRONICS, INC.
PRECISION TUNER SERVICE
General Headquarters: P.O. Box 272, Bloomington, IN 47401
Consult the white pages of your telephone directory for the address and number of your nearest PTS Service Center.
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November, 1976
Volume 26, No.
11
MORE
Electronic Servicing.
DEALERS
THAN EVER
BEFORE
HAVE US
WHERE THEY
WANT US!
4eeeeea,erexeeese eemmkre.
20 "Wireless" Radio Repairs-Servicing procedures for Royce
modular CB radios, and the basics of Phase -Locked Loops
(PLL) are explained-Marvin J. Beasley, CET.
30 Philco E21 Chassis...Circuits And Servicing, Part 2-Operation of the horizontal -sweep circuits are discussed, plus several
case histories John Simrell.
40 Servicing Electronic Organs, Part 6-If you repair old organs,
you'll need to know how to tune them. Here are two methods
of tuning by musical "fifths", starting from Middle "A"Norman H. Crowhurst.
45 Upgrading MATV
Systems-Many MATV systems badly need
repairs and upgrading. Suggestions are given for direct -mail
letters, signal -level tests, and typical repairs-Bert Wolf
52 Servicing GE Modular Color TV, Part 4-Several stages of the
19YC-2 vertical -sweep circuit are direct coupled. Theory, wave-
forms, and voltages are included-Gill Grieshaber, CET.
THE NEWEST
PTS SERVICE CENTERS
CHICAGO,
44771
IL
60630
N. Elston
312-725-2314
Les
Bertolini, Manager
OMAHA, NB 68132
5008 Dodge Street
402-558-1800
Donald Rausch, Manager
GRAND RAPIDS, MI 49501
1
134 Walker Northwest
P.O. 1435
616-454-2754
Dale Johnson, Manager
NASHVILLE, TN 37214
2426 A Lebanon
Rd.
615-885-0688
Steve Lewis, Manager
'.. :
.
.
'
SYRACUSE, NY 13204
418 Solar St.
.
315-475-2330
Melvin
ABOUT THE COVER
Don Clayton was too busy to pose for the photographer, as he
worked in Westcon's, a well-equipped CB service facility in
Kansas City. Picture is by Marvin Beasley.
DEPARTMENTS
Electronic Scanner
Symcure
Troubleshooting Tips
Reader's Exchange
4
8
11
12
Product Report
Book Review
Photofact
Advertiser's Index
64
65
67
68
Second class postage paid at Shawnee Mission, Kansas and additional mailing offices.
Published monthly at 9221 Quivira Road, Overland Park, Kansas 66212 by Intertec
Publishing Corp., 9221 Quivira Road, Overland Park, Kansas 66212. Send Form 3579 to
9221 Quivira Road, P.O. Box 12901, Overland Park, Kansas 66212.
Copyright, 1976, Howard W. Sams & Co., Inc. All rights reserved. Material may not be
reproJuced or photocopied in any form without written permission of publisher.
©
E.
Burns, Manager
DAVENPORT, IA 52805
E. River Dr., P.O. 187
2024
319-323-3975
Keith Pyatt, Manager
Now More Than 40 Locations
Offer Complete Tuner Service
VHF or UHF...510.95
UV Comb...$17.95
PTS ELECTRONICS: INC.
PPFC ISICiN TtINFF SFFVICF
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November, 1976
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Electronic Servicing
MEET
Editorial, advertising and circulation correspondence should be addressed to: 9221
Quivira Road, P.O. Box 12901, Overland Park,
Kansas 66212 (a suburb of Kansas City,
Missouri). (913) 888-4664
OUR FAMILY
EDITORIAL
RONALD N. MERRELL, Director
CARL H. BABCOKE, Editor
oF qRAbbERs
SHARON ELWOOD, Editorial Assistant
DUDLEY ROSE, Graphic Designer
EDITORIAL ADVISORY BOARD
LES NELSON, Chairman
Howard W. Sams & Co., Indianapolis
JOE A. GROVES, Technical Consultant
Howard W. Sams & Co., Indianapolis
CIRCULATION
GREG GARRISON, Director
EVELYN ROGERS, Manager
MODEL 4233 MICRO GRABBER
Tests high density packaging
ADVERTISING SALES
(a
egiofflommeill
Overland Park, Kansas 66212
suburb of Kansas City, Missouri)
Tele: (913) 888-4664
MIKE KREITER, Director
GLORIA PARMENTER, Production
REGIONAL ADVERTISING SALES OFFICES
MODEL 3925 MINI GRABBER
Tests conventional packaging
Indianapolis, Indiana 46280
ROY HENRY
2469 E. 98th St.
Tele: (317) 846-7026
froggamommilled
Greenlawn, New York 11740
CHUCK HORNER
P.O. Box 175
Tele: (516) 757-7863
Mountain View, California 94043
MODEL 4011 THREADED GRABBER
Accepts 6-32 threaded leads
DENNIS TRIOLA
2680 Bayshore Frontage Road, Room 102
Tele: (415) 961-0378
London W.C. 2, England
JOHN ASHCRAFT & CO.
12 Bear Street
Leicester Square
Tele: 930-0525
MODELS 3780 - 3789 GRABBER LEADS
10 choices of connectors other end
Badhoevedorp, Holland
John Ashcraft & Co.,
John J. Lucassen, Mgr.
Sloterweg 303
Tele: 2968-6226
Our Grabber family is five years old now, and
we're adding new members to keep pace with
the complexities of state-of-the-art electronic
packaging. Grabber is our name for a series of
test clips designed to simplify testing of electronic packages from conventional components to
maximum density DIP's. They're rugged, dependable, versatile, and very easy to use. Write for our
catalog and get the complete story on the whole
family of Grabbers. Find out why they are your
best solution to your electronic testing problems.
AVAILABLE THROUGH YOUR
FAVORITE ELECTRONIC
PARTS DISTRIBUTOR
MODEL 4225 MAXI GRABBER
Tests high rise packaging
1,
Tokyo, Japan
INTERNATIONAL MEDIA
REPRESENTATIVES LTD.
Shiba-Kotohiracho, Minatoku
Tele: 502-0656
'ABP
Member, American Business Press
Member, Audit Bureau of Circulations
ELECTRONIC SERVICING (with which is
combined PF Reporter) is published monthly
by Intertec Publishing Corp., 9221 Quivira
Road, Overland Park, KS 66212.
ELECTRONIC SERVICING is edited for technicians who repair home-entertainment electronic equipment (such as TV, radio, tape,
stereo, and record player), and for industrial
technicians who repair defective production line merchandise, test equipment, or in-
dustrial controls in factories.
All Grabbers shown actual size
Subscription Prices:
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year-$6.00,
2
years-
$10.00, 3 years-$13.00, in the U.S.A. and its
ITT POMONA ELECTRONICS
1500 East Ninth St., Pomona, Calif. 91766
Telephone (714) 623-3463, TWX: 910-581-3822
possessions. All other foreign countries:
year-$7.00,
2
years-$12.00,
3
1
years-
$16.00. Single copy 75 cents; back copies $1.
Adjustment necessitated by subscription termination to single copy rate. Allow 4-6 weeks
delivery for change of address. Allow 2-3
weeks for new subscriptions.
Robert E. Hertel, Publisher
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INTERTEC PUBLISHING CORP.
Subsidiary of HOWARD W. SAMS & CO., INC.
tPCIi9
NSN
a
Nct
àU61 RILL St.tt
EPC
capeºrìtnr
Electronic
Parts
Mallobin'
Merchandise Cabinets
Re.hargeable
Ba-teries
Duracell
Batteries
Resistors
"
.
Capacitors
Durata-
Controls and Switches
Sonalert
and Fliplape'
Audible Signais
Cassettes
PTC Semiconcuctors
Mallory-Richco Fastening Devices
eetutt a line like this, no wonder
ur Mallory distributor is a yes man.
He almost never has to say no. Which adds up to a lot of
single -source buying convenience for you.
Give your Mallory distributor a call. You'll like what you hear.
You'll like what he delivers.
MALLORY
MALLORY DISTRIBUTOR PRODUCTS COMPANY
a division of P. R. MALLORY 8v CO. INC.
Box 1284. Indianapolis, Indiana 40206: Telephone: 317-85e-3731
6 Registered trademark of
November, 1976
P. R. Mallory
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Co. Inc.
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3
flitmflIiscaN nor
news of the indus ry
About 50% of the 40 -channel CB radios have failed the FCC tests for chassis
radiation. A specially -designed test system measures the frequency error and power
output of all 40 channels, with results recorded by a printer. Next, a test for over modulation is made, then the chassis-radiation testing is done outdoors, followed
by visual inspections to make sure the sample is not a "lab queen" which has been
doctored to pass the strict specifications.
Frank Moch, Executive Director of NATESA, writes that our summary of his
beliefs about state -versus -city licensing of TV shops was not quite correct (see page
6 of September ELECTRONIC SERVICING). Frank does not think either kind of
licensing is needed, but state licensing would be preferable to Chicago licensing.
He writes, "The days of incompetent tube jockeys...are gone. They can't cope with
solid state, modules, and unitized chassis." "Our study reveals that 80% of all
(Chicago) complaints are against about six well-known sharpshooters. The answer
is for law -enforcement agencies to eradicate these offenders." "Continuous
maligning of ethical and professional servicers is doing nothing to assure
availability of service tomorrow. It will increase service costs, as in the medical
profession faced with many get -rich -quick malpractice suits, because abuse has to
have a price."
Sanyo has purchased for a reported $10 million the 57% of Warwick Electronics
owned by Whirlpool. Sears retains a 25% interest. TV manufacturing will be
continued by Sanyo Manufacturing Corporation, a subsidiary of Warwick.
If you think electronic magazines are too expensive, consider the "AMR Reporter"
(an anti -union publication) which has a subscription rate of $95 for 12 monthly
issues!
Technicians in the Chicago area are mourning the death of George (Gus) Cook,
one of the pioneers in electronic servicing. Also, John B. (Mac) McCulloch died in
July. He was active in NATESA-Detroit for 20 years.
RCA Sales Corporation has sold three branches of the RCA Distributing
Corporation, and is attempting to sell the remaining six. Facilities in Lenexa,
Kansas; San Antonio, Texas; and Chicago, Illinois now operate under new
management. Most of the former RCA employees and executives are being
retained. Although the sales reduce the cash tied up in the branches, RCA says the
main reason for the change is that independent distributors can do a better job in
those areas.
ban and a recall of all smoke detectors off the ionization type has been
requested from the U.S. Nuclear Regulatory Commission by the Health Research
Group, according to Retailing Home Furnishings. A small amount of the radioactive element americium is used in such detectors. Dr. Sidney Wolf, of HRG,
maintains that the amount of radioactivity from the detectors has been found to
cause cancer in animals, and that HRG 'believes the alternate photoelectric type of
detector will be more reliable in the long run. In rebuttal, Richard Cunningham,
an assistant director of the National Regulatory Commission, says the radiation
A sales
(Continued on page 6)
ELECTRONIC SERVICING
4
www.americanradiohistory.com
How to fit
119,000
,parts
in your
desk
dr _ er.
Our 1976 ECGTM
Semiconductor
Re-
placement Guide is the
compact way to keep the parts
you need right at your fingertips.
It's the most comprehensive
book in the industry.
There are cross-references for over
119,000 part numbers including domestic and -foreign entertainment, commercial and industrial types. Plus a brand new section on CB
radio replacements.
An expanded technical data section
gives you detailed specs on new transistors, ICs, rectifiers and high -voltage
dividers in the ECG line.
You can get your copy where you get
your parts-at your Sylvania distributor. It's
almost as good as having your own key to
his stockroom.
We're helping you make it.
November, 1976
SYLVANIA
5
www.americanradiohistory.com
i:°UIi!scaHHor
news of the ndus ry
(Continued from page 4)
from such a smoke detector is less than from a color TV, and so the danger
negligible.
is
Oldsmobile Toronados for 1977 have an electronic spark -timing microprocessor.
The "Microprocessor Sensing and Automatic Regulation" (MISAR) system is built
around a Rockwell 10 -bit custom microprocessor by the Delco -Remy division,
reports Electronic News. Engine speed, crankshaft position, manifold vacuum, and
engine coolant temperature are monitored, and MISAR determines the precise
time the high voltage is applied to each spark plug. An improvement of fuel
economy, and a reduction of emission are expected to result. Ford Motor Company
plans for 1978 models a microprocessor control of engine and exhaust gas
recirculation. Within two years, Chrysler Corporation expects to have
microprocessor control of the new lean -burn engine, and eventually might have a
total of three or four microprocessors in each car. General Motors is the only auto
manufacturer making IC's, at this time.
heart -defibrillator weighing only 8 pounds recently was demonstrated at
a medical convention. The machines operate from internal batteries. It was
estimated that as many as 200 heart -attack victims per day could be saved, if the
defib machine became as readily available as a fire extinguisher.
A pot-table
Have you ever heard of the "Shakespeare College of Electronic Knowledge"? Well,
perhaps it's not in a class with Harvard and Yale, but "Shakey U" operated for
two days in September at Hilton Head Island, South Carolina. Fifty sales
representatives of the Shakespeare Electronics and Fiberglass Division (CB and
radio manufacturer) earned their "Bachelor of Antenna Arts" degree. As you have
guessed, the theme was borrowed from colleges and universities, and the courses
covered electronic theory, product engineering and sales management.
6
ELECTRONIC SERVICING
Tuner Service Corpor
ele
95
b.)
b
U.S.A.
ONLY
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Major Parts
and Shipping
Charged
at Cost
One Year
Guarantee
MODULE REPAIRS
PROVIDES YOU WITH A COMPLETE SERVICE
FOR ALL YOUR TELEVISION TUNER REQUIREMENTS.
REPAIR
TSC has been
repairing private
brand TV modules
for over 2 years.
Expanded facilities
now include modules
for
VHF OR UHF ANY TYPE
(U.S.A. ONLY) $ 9.95
UHF/VHF COMBINATION
(U S
ONLY) $15.00
MAJOR PARTS AND SHIPPING
CHARGED AT COST.
Fast, efficient service at our conveniently located
.
Service Centers.
All tuners are ultrasonically cleaned, repaired,
realigned, and air tested.
RCA
GE
ZENITH
W. T. GRANT
J. C. PENNEY
WESTERN AUTO
GAMBLES
as well as Zenith
UNIVERSAL REPLACEMENT TUNER $12.95 (U.S.A. ONLY)
This price buys you a complete new tuner built specifically
by Sarkes Tarzian Inc. for this purpose.
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.
All
CUSTOMIZE
IF subchassis.
For free Price List and complete information write or phone;
TSC HEADQUARTERS, BLOOMINGTON, IND.
or any of the TSC locations listed below.
SAME DAY SERVICE
HEADQUARTERS
ARIZONA
CALIFORNIA
TSC
FLORIDA
GEORGIA
ILLINOIS
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WATCH US
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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.
ONLY ORIGINAL FACTORY PARTS USED
BLOOMINGTON, INDIANA 47401
TUCSON, ARIZONA 85713
NORTH HOLLYWOOD, CALIF. 91601
SAN MATEO, CALIF. 94402
MODESTO, CALIF. 95351
TAMPA, FLORIDA 33606
FT. LAUDERDALE, FLORIDA 33315
ATLANTA, GA. 30310
URBANA, ILLINOIS 61801
DOLTON, ILL. 60419
SKOKIE, ILLINOIS 60076
INDIANAPOLIS, INDIANA 46204
LOUISVI _LE, KENTUCKY 40205
SHREVEPORT, LOUISIANA 71104
BALTIMORE, MARYLAND 21215
SPRINGFIELD, MASS. 01108
ST. LOUIS, MISSOURI 63132
LAS VEGAS, NEVADA 89102
TRENTON, NEW JERSEY 08638
JERSEY CITY, NEW JERSEY 07307
ROCHESTER, NEW YORK 14615
GREENSBORO, N.C. 27405
CINCINNATI, OHIO 45216
CLEVELAND, OHIO 44109
PORTLAND, OREGON 97210'PITTSBURGH, PA. 15209
MEMPHIS, TENNESSEE 38111
DALLAS, TEXAS 75218
NORFOLK, VIRGINIA 23513
ST. LAURENT, QUEBEC H4N-2L7
CALGARY, ALBERTA T2H-1Y3
r-
GROW
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537 South Walnut Street
Tel. 812-334-0411
1528 S. 6th Ave.
Tel. 602-791-9243
10654 Magnolia Boulevard
Tel. 213-769-2720
600 S. Amphlett Blvd.
Tel. 415-348-3292
123 Phoenix Avenue
Tel. 209-521-8051
1505 Cypress Street
Tel. 813-253-0324
104 S.W. 23rd St., Bay 16..
Tel. 305-524.0914
646 Evans St. S.W
Tel. 404-758-2232
908 E. Main Street
Tel. 217-384-2052
1507-09 E. 142nd St
Tel. 312-841-4444
5110 West Brown Street....
..Tel. 312-675-0230
112 West St. Clair Street
Tel. 317-632-3493
2244 Taylorsville Road
Tel. 502-452-1191
3025 Highland Avenue
r
Tel. 318-221-3027
5505 Reisterstown Rd., Box 2624.
Tel. 301-358-1186
405 Dickinson St.
Tel. 413-788-8206
9577 Page Avenue
Tel. 314-429-0633
1412 Western Avenue
Tel. 702-384-4235
1139 Pennsylvania Ave
Tel. 609-393-0999
547-49 Tonnele Ave., Hwy. 1 & 9 .. .Tel. 201-792-3730
37 Pullman Ave.
Tel. 716-647-9180
2914 E. Market Street
Tel. 919-273-6276
1
7450 Vine Street
Tel. 513-821-5080
4525 Pearl Road
Tel. 216-741-2314
1732 N.W. 25th Ave., P.O. Box 10141 .. Tel. 503-222-9059
!
..r.
.
i
t
.515 Grant Avenue
3158 Barron Avenue
11540 Garland Road
3295 Santos Street
305 Decarie Boulevard
P 0 Box 5823, Stn. "A"
:...
Tel.
Tel.
Tel.
Tel.
Tel.
Tel.
412-821-4004
901-458-2355
214-327-8413
804-855-2518
514-748-8803
403-243-0971
r
Symptoms and cures
compiled from field reports
of recurring troubles
Y TCHN
T
1
Chassis-Zenith 25FC45
Chassis-Zenith
PHOTOFACT-1466-3
PHOTOFACT-1466-3
i
TO OTHER
SCREEN CONTROLS
TO RED
9-87
VIDEO
MODULE
LEAKY
5
MC
RED
0.01
I
11
11
11
11
SCREEN
1000 Q
25FC45
(b0
1 1
0
W13
+24
V
1
R212)
1 1
390 KQ
1 1
02
C
203
11
l00
R
uF
\1
11
BOOST
700 V
J
230 V
Symptom-Loss of horizontal sync
Cure-Check filter C203, and replace
Symptom-Low brightness (sometimes color smear
on
b -w)
Cure-Check C208, and replace
OPEN
it if open
it if leaky
F
Chassis-Zenith 13GC10
Chassis-Zenith 19GC45
PHOTOFACT-1 540-2
PHOTOFACT-1546-2
'
i i
9-120
VERTICAL
FLYBACK
U14
206
I I
500 u
C314
INTERMITTENT
F
MODULE
11
BLK
z
1 1
U22
2.7
S2
Symptom-Low HV (perhaps 12 KV)
Cure-Check RX232, and replace
Symptom-Height varies at top and bottom
Cure-Check R314, and replace it if intermittent
it
open
if
or
increased
t-
Chassis-Zenith 23GC45
Chassis-Zenith 25FC45 (others, also)
PHOTOFACT-1 558-2
PHOTOFACT-1453-3
FLY BACK
DELAY LINE
I
I14
L202
TO
SHORTED
9-89B
MODULE
0202 HORIZ OUTPUT
(206
IIE
T204
#1
9-88
1H
(R21
MODULE
+24 V
E
R21
DAMPER
O PEN
10520.68
TOW
JI
J
HORIZ PULSES
+128 V
foldover on left
Symptom-Loud hum, no HV
Cure-Check horizontal -output
Cure-Check the delay line, L202, and replace it if
place it if shorted
Symptom-No control of brightness; retrace lines;
open
J.
transistor,
and
re-
.1
ELECTRONIC SERVICING
8
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1976-1977
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troubleslootìmi
Send
in your
helpful
tips-we
óóe
pays
Blue picture; vertical -retrace
lines, General Electric 16JA
(Photofact 1335-2)
The raster was a bright blue,
with blue retrace lines. I checked
the collector DC voltages of the
three chroma/video output transistors (Q606, 0600, and Q604). The
[HAaM
uunouw at
collector was +21 volts
base was +5 volts
emitter was +2 volts
A forward bias of 3 volts, but
without collector current, indicates
an open transistor. I replaced
Q506, adjusted the AFC, touched
up the gray -scale screen color, and
returned the set to the customer.
Ed Pena
Oaks, Pennsylvania
No horizontal locking
Zenith 17EC45 (and others
using 9-57 and 9-70 horizontal
modules-Photofact 1377-3)
Visual examination of the hori-
COMPLETE SERVICE ON
ALL MAKES OF TV TUNERS
Maximum Time In Shop 24 Hrs.
(WE SHIP C.O.D.)
(Warranty: One Fut Year)
$9.95
zontal module located a burned
R808, which brings in horizontal
pulses that are integrated into saw -
Black &
White
or Color
teeth for the horizontal phase
blue output had near-normal voltage, but Q606 and Q604 measured
the same as the supply voltage.
This proved the two transistors
were cutoff (that is, had insufficient
forward bias).
detector. After removal, the 330 ohm R808 measured above 50K
ohms. Installation of a new one
gave good locking.
Since that first repair, I have
found four more open or burned
R808's. Evidently, a half-watt size
is not enough; late production 9-90
modules have 1 -watt resistors.
(Continued on page 17)
NEW 40 Channel
CB Receiver
SHIPPING
YOU PAY
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 re-
paired, 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
Test Set
Reduces test time
FOR ONE FULL YEAR
up to 40%
Improves accuracy, too. Has fully synthesized
channels. Internally leveled. Self -calibrating.
Single rotary knob for a full 40 channels. Continuous rotary attenuator calibrated in absolute
microvolts and dBm. Full transmitted power
absorption. Write or call today for complete
details.
23 channel LogiMetrics models will be upgraded
free of charge.
Q606 and Q604 did not have
enough positive voltage at their
bases. So, because the bases were
supplied by IC501, I replaced the
IC. This restored normal voltages to
the two transistors, allowing adjustment of good gray -scale tracking
without retrace lines.
However, the color bars did not
have enough red saturation. Some
extensive testing uncovered these
voltages at the 3.58 -MHz amplifier,
Q506:
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.
..,_...
Lo
etrics
121-03 Dupont Street, Plainview, New York, 11803
(516) 681-4700/1WX: 510-221-1833
RF Signal Generators, Frequency Synthesizers,
Traveling Wave Tube Amplifiers
For More Details Circle
GEM
CITY
TUNER SERVICE
Box 6G Dabel Station
1621 Mardon Drive
Dayton, Ohio 45420
(20) on Reply Card
November, 1976
11
www.americanradiohistory.com
Now you can stock only 300 semiconductors
instead of 112,000.
iUexcbanoe
There is no charge for listing in Reader's Exchange, but
we reserve the right to edit all copy. If you can help with
a request, write direct to the reader, not to Electronic
Servicing.
Needed: Operating/servicing literature, schematics,
and tube charts for B&K Model 650 Dyna-Quick
tube and transistor checker, 610 and TC-615 adapter
panels. Will buy, or copy and return.
Tom's TV & Electronics
R. R. #1. Box 218A
Horton ville, Wisconsin 54944
For Sale: Bell and Howell color TV course, complete,
sell all or parts; make offer.
Roman Watashi
2412 13th Ave. So.
Minneapolis, Minnesota 55404
Needed: 2EP4 picture tube for Philco TV, Model
H2010.
Larry Auman TV
Route 1, Box 368
Dover, Ohio 44622
12
For Sale: Heath Model I0-18 oscilloscope with
probes, perfect, $75. Also, Leader Model LSG -11 RF
signal generator, like new, $35.
C. J. Porcari
630 N. 65th Way
Hollywood, Florida 33024
Schematic, parts list, and other service
information for an old Crosley radio, Type 1121. Will
buy, or copy and return.
Raymond Friend
Needed:
236 W. Pearl St.
Butler, Pennsylvania 16001
Needed: 19-KHz transformer for Knight Model KG 765A stereo tuner. Original part #142-135L3,
273F6652. Will pay reasonable price for new or good
used transformer.
Allan Siirila
P.O. Box 561
Belvidere, Illinois 61008
Needed: Schematic and/or service manual for Martel
Model 40W AM-FM stereo receiver (made in
Canada), or address of company. Also, need manual
,for Tektronix Model 316 scope.
Stony Point TV
Route 9W, Liberty Drive
Stony Point, New York 10980
ELECTRONIC SERVICING
With RCA's SK Series you need
stock fewer different semiconductors than you'd have to with any
other major brand. Because our 300
devices can replace 112,000. And
they're all immediately available.
OEM Quality. You don't have to be
concerned about quality with RCA
SK's. They measure up to strict AQL
Standards to protect you from time wasting callbacks. Lets you make
more calls. And more profits.
See your RCA
Distributor for
a
copy
of the new RCA SK Replacement
Guide. Or send $1.00 to RCA Distributor and Special Products Division,
P.O. Box 85, Runnemede, N.J.
08078.
Rea
For More Details Circle
Wanted: Schematic and service data for a Grunow
Teledial cabinet type radio, chassis 10D. Manufactured in 1930's by General Household Utilities.
Will buy, or copy and return.
Larry Frank
13701 Force Street
Houston, Texas 77015
Needed: Vertical -output transformer, #TO -0061, for a
Muntz b -w TV combination, Model 3521W, chassis
A5001. Part can be new or used, but good.
E. J. McCain
Town & Country TV Service
600 Cate Avenue
Jonesboro, Arkansas 72401
Needed: Source of I RPM, 60 Hz, 120 -volt motors for
various Japanese -made digital clock radios. One is
marked "OMRON I RPM 60 Hz Japan". Motor
capsule is similar to Telechmn type, but much
smaller.
Bernard Serota
2502 South Phillip St.
Philadelphia, 19148
For Sale: Sprague/Jud Williams Model A transistor
curve tracer, good condition, $75.
Casco/Maitland
2241 Gillis Court
Maitland, Florida 32751
SK Replacement
Semiconductors
(77) on Reply Card
Needed: Complete series of "programmed instruction" publications (1964-1966) by Tektronix, titled
"'Semi-conductors, Diodes, and Transistors". I have
Volumes 1 & 2. Will pay shipping. Send price and
titles of other volumes, or I will copy and return.
Also, would like information on source of any "Programmed Instruction" course, manuals, or books on
digital concepts, electronics, etc.
S. O. Sellers
1504 51st Street West
Birmingham, Alabama 35208
Needed: Hammond organ service manual and schematic for Model B, C, or D, circa 1940. 2A3 and 56
tubes used in power amp. (Will buy complete
Hammond power amplifier, any condition.) Also,
need Sams 'Electronic Organs, Volume 1", #20188.
ATS Instrument Co.
P.O. Box 86
Farmington, Connecticut 06032
Needed: Schematic for Euphonics intrusion alarm,
Model #SA -3A, manufactured by Euphonies Corporation, Guaynabo, Puerto Rico 00657. Will buy, or
copy and return.
Gordon H. Williams
859 N.E. 121st St.
N. Miami, Florida 33161
(Continued on page 14)
November, 1976
13
www.americanradiohistory.com
Low cost tool for design
and trouble -shooting
Pocket Size
Slide -Switch
Resistance
(Continued from page
Needed: Pages one through six of the tube-chart book
for Model 157 Accurate Instrument Company tube
tester. Will pay postage, copy and return.
D. L. Konicki
4443 N. Greenview Avenue
Chicago, Illinois 60640
Substitution Unit
still only
$ 58
Wanted: Howard W. Sams book #24014 "Single
million step range
1% accuracy resistors
Unique in convenient size
Rugged construction
Over
13)
11
Small enough to take anywhere in your pocket, this aluminum housed unit delivers a very broad range of resistance steps.
Excellent for both development and repair work.
Half -watt 1% tolerance resistors give an accurate range from
to 11,111,110 ohms, in one -ohm steps. Has three binding
posts, one to ground case.
Available now from stock. Catalog No. 7092-236. Cash savings
available, see coupon. Write, or call (804) 264-2858. Phipps & Bird, Inc.
Units (i $58 each. (Check enclosed less 5%
Please send
cash discount)
Units << $58 each C.O.D. (Phipps & Bird will pay
Send
C.O.D. charges)
1
Sideband: Theory & Practice." Quote price and
condition.
Barnes TV & Radio Service
118 West Main Street
Camden, Tennessee 38320
Instruction book or service manual for
Model 30-B Fleet Courier receivers. Will pay for
copying, or will copy and return.
John Haver))
Specialist, Electronics
Education
Oregon Department
Needed:
942 Lancaster Drive, N.E.
Salem, Oregon 9731G
Name
Needed: Schematic or service manual for Bradford
TV, Model 1004B30, W.T.G. #30-55988. Will buy, or
Firm
Address
Zip
Ask your dealer, or contact:
City, State
ppio alp
G3D, va¢.
O
C7 0
Manufacturers of Scientific Instruments
P.O. Box 27324 Richmond, Virginia 23261 Phone: 804/264-2858
For More Details Circle
copy and return.
William S. Reid
18506 Indiana
Detroit, Michigan 48221
(Continued on page
18)
(21) on Reply Card
Fix it Quick...
with an
Ungar Cordless Quick -Charge
Soldering Iron
Cordless portability
Quick 4 -hour charge
Holder automatically charges
high performance NI -CD battery
Rigid coaxial tip rotates to
desired working position
Easy -touch switch, tunne, light
Quick heat -up
SPECIAL OFFER
Free Micro -Spade Element Tip
Present this coupon to your local participating
Ungar electronic distributor and receive a FREE
#195 Micro -Spade Element Tip worth $1.99 with
your purchase of a #200 QUICK -CHARGE
CORDLESS SOLDERING STATION.
HURRY!
Offer EXPIRES December
(Unga)
Division of Eldon Ind., Inc.
1,
1976.
Compton, CA 90220
For More Details Circle
(22) on Reply Card
ELECTRONIC SERVICING
14
www.americanradiohistory.com
(Continued from page 11)
These defects remind us that
both the sync pulses and a sawteeth
sample from the horizontal -sweep
circuit are necessary for proper
operation of this type of phase
detector.
George Persico
Thiells, New York
0
one Genefator
J
1
SAWT00iH
C01.00
pattern below. Use
it for checking and
adjusting gray scale
or for
tracking
checking effects of
video level upon horizontal sync. Use it
to check for reversed yoke connections vertical, horizontal or both. Use
it to check low frequency video response. It can save
you time, trouble
and money! Write
.°.°;
ATC- I
GENERAL TELEVISION
SERVICER
SHAPER
Editor's Note: This typical defect
has been reported and published
several times, but we are telling it
again for any. technicians who
might have missed it before. Refer
to page 30 of the August issue of
ELECTRONIC SERVICING for
another case history.
One of the most
useful, UNIQUE patterns of the ATC-10
is the GRAY QUAD
$299.95
PAT. PEND.
-
Extra wide range RF/IF attenuator for
testing receiver sensitivity.
HATCHDOTS - versatile composite pattern for dynamic & static convergeance
plus other checks.
COLOR BARS pattern with 6th bar
marked to make your job easier.
3.58 MONITOR pattern for oscillator
frequency checks with no need to short
the AFPC test point.
RED RASTER pattern for checking and
adjusting purity at the flip of a switch.
High level, 75 ohm output provided.
2 year factory warranty.
30 day money back guarantee.
2 volume owner's manual available separately - $1.00.
us.
American Technology Corporation
225 Main Street, Dept. 11A, Canon City, Colo. 81212
Credit card & COD phone order, accepted. Same day shipment. (303/ 2751199
Insensitive remote
Zenith Chassis 23DC14
(Photofact 1306-3)
The complaint against the
remote -control operation was that
the hand unit had to be very near
the TV. else it would not change
channels. I pulled the remote
amplifier, transducer, and hand
unit for the shop.
While checking the DC voltages
at the amplifier transistors, I found
a high collector voltage for Q1, the
first amplifier. Much additional
testing proved nothing, until I disconnected the transducer. That
reduced Q1's collector voltage to
normal.
After I obtained a new transducer and connected it, the abnormal voltage was gone and the
sensitivity of the remote was good.
'Ihe defective transducer measured about 20K ohms, and it
should have checked open. Strangely
enough, the bad one worked okay
in a tube -equipped remote!
In my 43 years of servicing, I
have replaced only one other transducer.
D. W. Alleeson
Los Angeles, California
November, 1976
For More Details Circle
1.
rxt. I.
(3) on Reply Card
DIGITAL MULTIMETERS
NLS proves NLS' DMMs have more capability
at lower prices.
THE VOLKSMETER FAMILY
LM
SERIES
Features Include:
Battery
Super Rugged - ideal for field service use.
Expowered with batteries and charger unit included.
clusive NLS fuseless protection in kit mode - up to 500 vdc
Overload
or rms ac maybe applied without damage.
OpAutomatic zeroing and polarity.
indication.
Large 0.3" LED
erating temperature - 0° to 45°C.
Small size: 1.9" H x 2.7" W x 4.0" D.
display.
Six optional shunts for current measurement -LM -3.5
includes three shunts in values of 10 mA, 100 mA and 1A.
LM -3
LM -3.5
LM -40
LM -4
DIGITS
PRICE
1
mV
3
$125
VDC & VAC
1V, 10V, 100V & 1000V
±1% Rdg
±0.5% Rdg
1
mV
3-1/2
$147
OHMS
10.1% Rdg
1
µV
4
$190
±0.03% Rdg
1
µV
4
$227
DC ACCURACY
RANGES
MODEL
1 k(2,
101át, 100 k4,
1 MI2 &
10 NM
RESOLUTION
Non -Linear Systems, Inc.
Originator of the digital voltmeter.
Box N, Del Mar, California 92014
For More Details Circle
See your local distributor!
Distributor inquiries invited.
Telephone (714) 755-1134
(4) on Reply Card
17
Shale
(Continued from page
*
14)
For Sale: B&K television analyst, Model 1075. and
Dyna-Sweep circuit analyzer A107: best offers.
Max Stern
2011 Picton St.
Ocean, New Jersey 07712
Needed: One 4GZ5 tube.
Sam Yuppa
16191 Melody Lane
Huntington Beach, California 92649
Needed: Schematic or technical manual. /òr Bell Boy
personal pager. Bogen Model TR -54B.
Derek Watson
R.R. 3
Bridgewater.
Nova Scotia, Canada
Needed: A Setchel Carlson Model U800 color chassis,
or any plug -ins .for it.
Malcolm McCarty
4401 Wildwood Road
Dallas, Texas 75209
Needed: Service information on Mercury vacuum
tube voltmeters. Model 1700C in particular.
R. S. Hamilton
4509 Richardson
Fort Worth, Texas 76119
Needed: Schematics and
Century VTVM, Model
schematic of probe. Also,
wiring diagrams /br Eico
operating manuals for
also probe, or
need schematics and/or
VTVM, Model 232: and
Supreme Instruments Model 542 millimeter.
Allen C. Fryou
3735 Fairmont Drive
New Orleans. Louisiana 70122
VT-10:
Needed: Operating and servicing literature or
schematics ,for Solar capacitor analyzer Model
CB -1-60. Will buy, or copy and return.
Tom Garz
R. R. #1, Box 218A
Hortonville, Wisconsin 54944
Needed: Service manual .for a B&K Model 1450
scope. Will buy, or copy and return.
Dan L. McGrath
616 Paris Ct.
Columbia, Missouri 65201
For Sale: One Sencore CR143 picture -tube tester/
rejuvenator. just overhauled and calibrated, with all
manuals and test sockets. .for $30 or best offer.
Al Hawkes
U.S. Route 302
Westbrook, Maine 04092
18
ELECTRONIC SERVICING
Just Tear and Get your Share.
RCA's Super Prize Program is Back by
Popular Demand! As before, just save your
RCA entertainment receiving tube carton
ends and color picture tube warranty
to earn
serial number stickers*
valuable awards:
-
Pick up your copy of the RCA "Tear and Share
'76" Prize Book, saver envelope and gift order
form at your participating RCA distributor.
You have until November 30, 1976 to tear 'n
share in RCA's bonanza of great gifts. RCA
Distributor and Special Products Division,
Cherry Hill, N.J. 08101.
Lots of great merchandise premiums. Choose
from a wide selection for yourself, your
family, or your home.
Money -saving
discount certificates, good toward purchases
of more RCA receiving and color
picture tubes.
*Save the receiving tube carton end that is not
marked with the tube type number, and the warranty
serial number sticker that appears above the
warranty envelope on the upper right hand corner
of the color picture tube carton. One warranty
serial number sticker is equal in value to
20 receiving tube carton ends.
RC"
Needed: Schematic and/or service manual ,for I.T.T.
Industrial Products Division medical monitor solidstate oscilloscope. Type KM402, Serial 7284, (12"
screen). Any information would be helplìd. Will buy,
or copy and return.
Joe Amenta
534 W. Addison St.
Suite One South
Chicago. Illinois 60613
For Trade: Will trade radio and TV tubes
for test
equipment and Rider's radio manuals.
Troch's TV
290 Main St.
Spotswood, New Jersey 08884
Needed: Schematic for Zenith transoceanic portable
radio. Model 8G005TZ/. Will buy. or copy and
return.
Walter J. Theurer
Fulton -Montgomery Community College
Johnstown. New York 12095
For Sale: B&K /460 scope. B&K color bar generator,
Sencore 7 -in -1 bias supply, like new: all for $300.
John Durkin
4231 Ely Ave.
Bronx, New York 10466
November, 1976
Needed: Service data for a Model 2085 8 -track tape
recorder/player by Mayfair Sound Products. Also,
need service data for a stereo receiver Model
STA -2100 manufactured by Monarch Electronics
International.
John: Nicoll
18812 Cypress
Tinley Park, Illinois 60477
Needed: Power transformer for Jackson oscilloscope
Model CRO-2 (part #14-59): and a power transformer
for Mercury tube checker Model 301. (part #10066410
or 10-1-6).
St. George Electronics
P.O. Box 7. Water Street
St. George, Bermuda
Needed: One power transformer 54-26 for Heathkit
Model 0-12 oscilloscope.
Joseph J. Bubis
66 Pumpkin Ground Road
Stratford, Connecticut 06497
Schematic and/or assembly manual for
Lafe{vette Genometer Kit 38-1001, Model 156, manufactured by Accurate Instrument.
Bill's TV Service
William E. Schaefer
1136 Limekiln Pike
Ambler, Pennsylvania 19002
Needed:
19
LL
Wireless"
Radio Repairs
Servicing the "wireless", modular CB transceivers by Royce is different
from repairs of conventional radios having circuit boards and many
connecting
wires. The basics of Phase -Locked Loops (PLL) also are explained.
ocnox ..E
In
GAIN
....cB O«_.OF' LOC..O[
.
TUNE
Royese
outside appearance of
the Royce Model 655 CB
radio transceiver gives no
hint of the unusual construction inside.
The
By Marvin J. Beasley, CET
Technical Associates, Inc.
Wires Versus Modules
We technicians have no reasons
for judging the merits of various
kinds of wiring or mechanical
layout, except as they affect either
the performance, or the difficulty of
making repairs. And we tend to
ignore most claims made by manufacturers about the products. In
fact, most technicians might be
described as being blasé.
Even so, my first glance inside a
Royce "wireless" type of CB radio
transceiver startled me. Much of
the works seemed to be missing
(Figure 1), as though the radio
might be a sample or a mockup.
But a closer look revealed a
"mother" circuit board (Figure 2),
into which the terminals of four
modules and a shielded synthesizer
were inserted and soldered. The
mother board had all of the
copper -foil type of connecting wires
on it, and this eliminated the usual
clutter of wires that tend to hide
the components and give an untidy
appearance to radios of conventional construction.
The modules are spaced rather
close. together. In fact, there's not
enough room for any extensive
testing on the modules. A solution
is shown in Figure 2; unsolder the
terminal pins, remove the module,
place it in the same position below
the circuit board, solder the pins,
and you have unlimited space on
both sides of the module for "live"
tests.
Figure 3 pictures three of the
modules, removed from the radio.
And Figure 4 shows the conventional 23 -channel Royce synthesizer, which uses 14 crystals and 4
transistors. Not shown is the Phase Locked Loop (PLL) module and
switch; in appearance it is merely a
20
shielded box.
Good accessibility to most circuits and components is shown by
the two pictures in Figure 5. Both
metal sides have cutouts.
Servicing Procedures
Efficient servicing requires you to
match the trouble symptoms with
the functions of the basic circuits.
Now then, if you can do that
(without problems) from the full
schematic alone, you need nothing
else. But, when the maze of
symbols interfere with your logical
analysis, you should have a block
diagram (Figure 6).
Incidentally, the service literature
from Royce is excellent. It includes specifications, troubleshooting charts (Figure 7), voltage charts,
and alignment instructions.
If you are tired of squinting over
the usual 3 -inch schematic, the
Americanized 11 -by -17 -inch schematic (that's supplied with each
ELECTRONIC SERVICING
www.americanradiohistory.com
Fig.
1
The Model 655 seems to be
unfinished: the usual inaze of connecting wires
radio) will be a relief.
Warranty
Although the terminals of the
Royce modules are soldered to the
mother board (as a precaution
against intermittent connections in
rough mobile service), any module
can be unsoldered and removed in
less than 5 minutes. Therefore, the
Royce warranty provides for the
no -charge exchange of a new module for the defective one, and for
labor to replace (not repair) the
module.
Royce appoints warranty stations,
but independent shops can buy
service manuals, modules, and components from the factory for out of -warranty repairs.
Of course, if the radio is out of
warranty, you either can replace
individual components on the modules, or obtain and replace complete modules; it's your choice.
The exchange price of modules is
about 25% of the list price of new
modules.
Phase -Locked Loops
It seems likely that all of the new
40 -channel CB radios to be sold
after January 1 of 1977 will employ
frequency synthesizers of the Phase Locked Loop (PLL) type, rather
than ones using quartz crystals.
The reason for this prediction is
is
missing.
reception of radio signals by locked phase signals. This method was
developed in the search for a circuit
to compete with the superheterodyne. However, both the cost and
complexity were excessive, and PLL
circuits never became popular for
AM reception.
Even so, other simple applications of Phase -Locked Loops have
been used over the years. For
example, all of the frequency horizontal oscrystals. A crystal synthesizer for 40 locking circuits for
are PLL's.
receivers
in
TV
channels might require 21 crystals, cillators
Con-Frequency
Automatic
FM
3
while a PPL synthesizer could use
samwhich
operation,
(AFC)
trol
crystals and 10 IC's.
"S" -negative
-zero
Very little information has been pled the positive
FM
from
the
voltage
output
curve
released about the Royce PLL
the
tine
-tune
it
to
used
and
detector
system; however, we can give some
was (and
also
frequency,
oscillator
that
history
general data and
PLL action. And what
should help you understand basic is) a type of
locking circuits?
-oscillator
color
of
phase -locked loops.
"Chink of the ones that had two
diodes to compare the phase of
History of PLL
sigIn 1932, British engineers de- burst and 3.58 -MHz oscillator
DC
a
came
diodes
the
From
nals.
scribed a system of synchronous
the high cost and scarcity of
21
November, 1976
Fig. 2 A mother" circuit board supplies the copper
-bonded connecting wires, and the module pins
are
soldered to this board. To obtain more room for power
-on servicing, the modules can be removed
and
soldered on the bottom of the board, as shown.
A
voltage used to vary the capacitance
of a reactance stage. In turn, the
reactance circuit determined the
final frequency and phase of the
3.58 -MHz oscillator. Those circuits,
too, were simple examples of PLL,
although we didn't call them by
that term.
8
C
Fig. 3 These are three Royce modules. (A)
The U4 module has the transmitter
pre -driver and output stages; (B) the audio/modulator
stages and the modulation transformer are on the U3 module; (C) U2
module contains the IF stages.
Notice that all of these circuits
forced the frequency of an unstable
oscillator to keep in step with the
frequency of some standard.
Of course, having a PLL and a
crystal oscillator which both produce the same frequency in a CB
radio would not be desirable. But a
PLL would have great value if it
could generate a phase -locked Signal at many different ratios (either
higher or lower) of frequency relative to the standard stable oscillator. Even then, it's true that the
two signals supplied to the phase
comparator ALWAYS have identical frequencies and a 90 -degree
phase. Proper operation of any PLL
depends on these primary conditions.
When the standard and the
variable oscillators are locked to gether (even though the locking is
between octaves, sub -octaves, or
22
EL V rtUNIL, SERVICING
i
Announcinga
Exlusive New
Broadband
MATV Amplifier
with Automatic Overload Control
0
GH
H/C0110
.
felt
C9
sewer*
Mt
AUTOMATIC
w,..... .oc
....--.,aC,
GIEAp,tiTAR
a+
NINTBAe410*e
TFRAM P
._.
OUTPUT
HIGH BAND
NJ
MOCEL
JGQRV
del itaoueIX
3662:.
VHF-TV/FM
AMPLtF1ERD D
Model 3662
Just set it... and foret it.
Automatic control for
input variations of up :o 20 dB
Eliminates nuisance service
calls
45 dB Gain, VHF High Band
+52 dBmV Output Capability
Separate Lo and
Hi VHF
band
controls
Operates at full output rating
Switch selectable AOC or
MAN operation
Lightning protected
Universal rack or surface
mounting bracket
UL listed
Jerrold Model 3662 is the only
broadband MATV amplifier with
output signal levels automatically
controlled. This exclusive feature
permits use of the full output
capability of a broadband
amplifier without fear of overload
due to input signal fluctuations.
AOC operates to:
1. Prevent overloading the
amplifier when input levels increase.
2. Increase amplifier gain to
compensate for signal fades.
cross system
3. Prevent
one
only
if
modulation even
channel level increases or
fades.
TRY THE 3662 FOR YOUR NEXT MATV INSTALLATION
JERROLD ELECTRONICS
GENERAL INSTRUMENT CORPORATION
For More Details Circle
(5)
on Reply Card
November, 1976
www.americanradiohistory.com
23
other ratios), the output -signal fre- of a simple basic
PLL circuit.
quency will have the same drift as Except for a couple
of details, it
the standard signal. If a CB radio could be the diagram
of horizontal
has 40 channels from a PLL, all 40 locking, color
locking, or AFC
will have the same drift and correction. Error
-correction amplipercentage of accuracy. This is an fiers aren't always
used
important advantage, because it's circuits; and for AFC, in locking
the phase of
much easier to stabilize one oscilla- a tuned circuit is
the standard,
tor than several.
rather than a separate master signal. Any loop system needs ampliBasic PLL
fication somewhere, for high gain is
Figure 8 gives the block diagram essential for precise correction
and
Fig.
The U6 Royce module
crystals and four transistors.
4
contains
a
conventional synthesizer with
14
operation over wide
lock -in ranges.
pull -in and
PLL differences
In 7V circuits, the DC error correcting voltage from the phase
comparator (detector) often is zero
when the oscillator needs no correction, and it swings negative or
positive as required to maintain the
locking and phase.
Other kinds of PLL circuits
might operate with a correction
voltage of a designated positive
value, with the actual voltage
swinging up or down from that
point to hold the locking.
PLL phase -comparator circuits
usually do not have two diodes as
rectifiers. Instead, a flip-flop multi vibrator might be used, one which
varies the width of the output
pulses according to the phase
difference between the input sig-
nals. After processing and filtering,
the output pulses become a DC
voltage whose value depends on the
width of the pulses.
Also, the voltage -controlled oscillator probably would be tuned by
a varicap diode, whose capacitance
is determined by the DC control
voltage from the phase comparator.
In that case, the comparator is
arranged so the control voltage is
highest when the phase difference
between the inputs to the comparator is the greatest. The error correction voltage pulls the voltage -controlled oscillator in the
direction of the standard input -
signal frequency until locking
occurs.
Adding dividers
A I'LL system can be fooled into
believing the voltage -controlled os-
cillator has the same frequency as
the input standard by adding a
digital frequency divider to the
sample of oscillator signal that is
fed to the comparator (see Figure
9).
Suppose the frequency divider
gave a reduction of 10 times. When
the error -correcting DC voltage
Fig. 5 These two pictures illustrate the good accocsibility
to roost components.
Both side panels have cut-outs.
brought the two signals at the
phase comparator into lock (same
frequency and phase), the output
signal from the Voltage -Controlled
Oscillator (VCO) would have 10
times the frequency of the standard
signal input to the comparator.
This frequency -multiplied signal
would have the same stability of
frequency as the standard signal.
24
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i
A NEW LOW-COST,
DUAL -TRACE SERVICE OSCILLOSCOPE
FULLY BACKED BY TEKTRONIX
Now for only $595 you can get a
portable, 10 MHz dual -trace service oscilloscope. The 18 lb TELEQUIPMENT D61a has front -panel
controls that are easy to understand, easy to use. Full -sensitivity
X -Y gives you vector displays that
are in true phase relationship-displays that you can rely on. And
automatic selection of alternate or
chopped mode and automatic selection of tv line or frame triggering
make this oscilloscope ideal for
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D61a features a bright 8 x 10 cm
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Service Centers nationwide. Call
your nearest Tektronix Field Engineer or circle the reader interest
For Technical Data Circle
November, 1976
(6) on Reply Card
For Demonstration Only Circle
(7) on Reply Card
number below for specifications
and ordering information on the
new D61 a and other low cost TELEQUIPMENT Oscilloscopes.
U.S. Sales Prices FOB Beaverton, Oregon
I
TEEEQUIPMENT
P.O. Box 500
Beaverton, OR 97077
25
L)
C
1
I
I
4
C
Q
CL
O
a
Q
LD
S
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It?
1-
r
t
L7
5
1
x
0
CC
X
.0
X
t
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t
*yI
T
f -I
f
PLL circuits in general is the many
are used with both signals applied
to the phase comparator, the VCO
can be forced into operating at any
one of a large number of stable
frequencies. Also, additional crystal
oscillators can be switched in, when
needed, to provide even more
frequencies.
Notice that the output signal
from a PLL can be much more
pure than it is from other synthesizers which mix two frequencies in
So far, the performance has not
been spectacular; after all, a series
of doublers could have given 4, 8,
16, or more amounts of frequency
change. But, there is more.
The fixed divider can be replaced
by one giving a series of different
divisions, the number controlled by
a switch. Such a circuit is called a
"programmable" or "variable" divider (even though it is not continuously variable, but has definite
(almost endless) array of functions
that can be done with variations of
the basic PLL circuit.
For example, SCA demodulation
of background music on FM stations can be done with one IC, six
capacitors, and ten resistors. AM or
FM demodulation is nearly that
simple. The voltage -controlled oscillator can be made to lock to a
weak signal that's buried under
noise, thus giving the effect of
amplification and tuning, but requiring fewer components. Or, a
PLL can be locked to the harmonic
of a signal, for another kind of
non-linear circuit, because there
are no sum -and -difference frequency products in the output (only
a
steps).
Also, a divider (either fixed or
variable) can be added between the
the normal oscillator harmonics).
One of the fascinations about
standard signal and the phase
comparator. When variable dividers
RECEIVER
Conditions:
(A)
LOW OR NO
OUTPUT PIN #3
(L12)
y
10.7 MHz
(OUTPUT =1 mV
PIN #2 PLL
YE S
GO TO U2
CHECK BELOW
(B)
-NO
37
Inject 27.115 MHz signal
at
(100µV level,
1
NO
mod
@
antenna input
kHz)
Squelch at minimum.
--.
MHz OUTPUT
PIN #19
3070
B+
(9V)
OUTPUT
9 V
NO
PIN
PIN #22'
YES
YES
YES
REPLACE U1
(Uil
PLL
PLL
N
#1
7
AGC CHECK
REPLACE
CHECK SOLDER
PLL
CONNECTION
(BELOW)
OK?
Nu
YE S
REPLACE U2
REPLACE U1
AGC CHECK
Conditiont
(Al Inject 455 kHz (1 mV) at pin
(B)
15
(U2), 30% mod
@ 1
kHz
Squelch ?t minimum
1(
2)
3)
Disconnect pin
6 (U1),
then apply power.
nject signal as per conditions above.
Measure AGC voltage at pin 13 (U2) for the following
I
generator settings;
P13 VOLTS
1
Fig.
7
mV
.45
100µV
.54
10µV
1.25
Typical of the Royce service aids is this troubleshooting chart.
27
November, 1976
www.americanradiohistory.com
DC
LOW-PASS
DC
CONTROL
FILTER
Fig.
8
diagram
the basic block
of a Phase Locked Loop (PLL) is the
san:e as many circuits
used in 1V receivers.
When the frequency of the
VGO is wrong, the phase
comparator produces an
error -correction DC voltage
which varies the frequency
until it is in lock.
frequency multiplication.
Unwanted sidebands (even those
too close to be filtered out) can be
removed by locking a PLL to the
fundamental.
Laboratory frequency standards
have been built at low cost by using
a PLL that is locked to WWV, the
National Bureau Of Standards station.
These are just a few of the
possible applications for PLL's.
Royce PLL
At this time,
Royce
does not
recommend field repairs of the
Gyro -Lock PLL modules. For that
reason, the following circuit explanation is not detailed.
Even so, we can learn part of the
operation from Figure 6. Of the
three crystal oscillators, two are
used together at a time. One
variation from the basic PLL circuit
is that the variable -frequency signal
is not obtained solely from a VCO,
N
PUT
PHASE
ERROR CORRECTION
AMPLIFIER
COMPARATOR
AC SAMPLE
but by heterodyning the 36.38 -MHz
and VCO signals in a mixer, then
the resultant is amplified and
divided by a programmed divider
before it reaches the phase com-
parator.
To obtain the transmitting frequency (26.965 MHz for Channel
1), the 10.695 -MHz signal is mixed
with the output of the VCO. For
receiving, the VCO output supplies
the first mixer, producing a first IF
of 10.695 MHz, which is hetero=
dyned down to 455 KHz by a signal
from the 10.24 -MHz oscillator.
Frequency and frequency drift
during transmitting depends on
both the 36.38-MHz and 10.695 MHz oscillators. All channels will
have the same percentage of frequency error.
Frequency and frequency drift
during receiving are functions of
both the 10.24 -MHz oscillator and
the 36.38 -MHz oscillator, plus the
variation of the 10.24 -MHz fre-
LOW-PASS
FILTER
VOLTAGE CONTROLLED
OSCILLATOR
AC OUTPUT
quency by the "Delta" control. This
control can vary the oscillator frequency during receiving by as much
as 1.5 KHz, to allow proper tuning
of any out -of-tolerance stations.
Length and position of the connections to the channel switch are
not critical because only DC voltages go there.
Comments
Modular design of CB transceiver radios, and the consequent
elimination of most connecting
discrete wires can be important by
permitting faster (more profitable)
repairs. Of course, the modules
must be readily available through
an exchange program, and the
service data should be of good
quality. All of these desirable things
are true about Royce "Wireless"
models, and we can hope that other
manufacturers will follow a similar
plan, which would help the CB
repair business.
ERROR CORRECTION
AMPLIFIER
PHASE
COMPARATOR
FREQUENCY
DIVIDER
VOLTAGE CONTROLLED
OSCILLATOR
reefflimimmi
Fig. 9 For use in frequency synthesizers, a frequency divider is added so
the VCO can be locked to frequencies other
than the standard.
28
ELECTRONIC SERVICING
www.americanradiohistory.com
THE CB SERVICE MONITOR
BY MEASUREMENTS
MODEL CB 27E
$495.00*
Low-cost, rugged, portable instrument for accurately checking,
trouble shooting and aligning Citizens Band Transceivers
operating in any of 40 Channels presently assigned.
Phase -locked loop circuitry referenced to "AT" cut
crystal.
Monitor and transmitter are both protected against
overloading if transmitter is accidently keyed.
Provision for adding future channels.
Built-in transmitter power meter.
Built-in speaker monitors transmitter frequencies down to
zero -beat and provides on -the -air voice evaluation.
Write or call for additional information.
*F.O.B. Manchester, N.H.
McGRAW-EDISON COMPANY
Edison Electronics Division
Grenier Field Municipal Airport, Manchester, N H 03103
(603) 669-0940 TWX 710-220-1747
November, 1976
For More Details Circle
(8) on Reply Card
29
Philco E21
Chassis...
Circuits
and
Servicing
Power supplies of the Philco
E21 chassis were covered last
month, including the safety
shut -down circuit that kills the
horizontal drive. This month,
the horizontal -sweep circuits
and several case histories are
examined.
Noise inversion
Instability from impulse noise is
minimized by separating the pulses
from the video signal, inverting the
phase, and feeding these clipped
and inverted noise pulses into the
video where they cancel the noise
pulses of the original phase. Most
of this occurs inside the IC, where
+20
3300
S2
testpoint, the oscillator hold -in
range is so tight that it's difficult to
know where to adjust the core of
the oscillator coil. No hold control
is provided for the customer, so it's
up to you to adjust the frequency
accurately.
IC400
068
1
4
t
POS VI DE01-4.-
2
510 Q
1000
S2
3.5V
0.3V
1.7 V
10.8 V
5
-3.5
6
7
8
560KS2
TO
DC VOLTAGES
4
3
SS
INPUT
Sync separation
Although the transistors are inside the IC, the network that's
always supplied at the input of the
sync separator is external. Positivegoing video emerges at pin 4, goes
through the network, and goes back
into the IC at pin 5.
Testpoint "SS", at pin 5, allows
you to observe with a scope the
video after it has passed through
those filtering components. But the
testpoint also has another useful
function. When you ground that
point, all sync (both vertical and
horizontal) is eliminated, thus allowing you to accurately adjust the
frequency of the horizontal oscillator. Otherwise, if you don't use the
Functions Of IC400
Four functions are accomplished
inside one integrated circuit, IC400
(Figure 1). These four are: noise inversion; sync separation; phase
comparison and oscillator control;
and horizontal oscillation.
Part 2/By John Simrell
you can't trace it. But the inverted
noise comes out of the IC at pin 2.
9
10
11
11 V
12
20 V
V
13
20V
17.2 V
14
3.3
5.8V
15
5.0V
1.6 V
16
SYNC SEP
4
c4141
Ip
68
'Itiii7
NEGATIVEGOING
VIDEO
1
5
C402
I
HORIZ
DRIVER
Q400
HORIZ
FREE)
12
:75
13
14
INVERTED NOI SE
470
15
S2
11F
V
8
50 V
HORIZ OSC
1200
VIDEO & AGC
S2
470
11
S2
l
10
+20 V
+ 112 V
3300
16
1200 f2
S2
(SC R43-C)
100
(sc404)
o
"50 V0F
SHUT DOWN
10K0
+68 V
C
IC400 SYNC SEP
TO
pF
,022
F
68052
220 pF
3300
i(
820K0
560
S2
+20 V
.033
HORIZ
PULSES
PHASE DETECTOR
www.americanradiohistory.com
6.1V
0V
.001
20 V
V
After separation of the sync tips
from the composite video, the
signal is divided, with the vertical
sync emerging from the IC at pin 6,
and the horizontal -sync pulses going internally to the phase detector.
Some components of the phase
detector are mounted outside the
IC (those tied to pins 7, 9, and 11),
and these points can be used to
These are the
main components
of the horizontal oscillator circuit
in the Philco E21-4
chassis (the Sylvania E21
same).
observe the waveforms.
is
the
Phase detection and oscillator control
Horizontal pulses, which are filtered into a sawtooth waveform for
the phase detector, come from the
horizontal -blanker stage, and they
enter the IC at pin 8. Of course,
both sync pulses and a sawtooth
from the horizontal -sweep circuit
Square waves from the oscillator
some components are external to emerge from pin 15. Last month,
the IC, and they include B+ and we described how the shut -down
oscillator coil parts that are con- circuit (which was triggered by exnected to pins 12, 13, and 14. cessive voltage of the +112 -volt
Notice that no customer horizontal- supply, or the excessive current of
the +29 -volt supply) forced SCR430
hold control is provided.
to short out most of the amplitude
at
pin
taken
A scope waveform
of square waves coming from pin
not
the
or
whether
will
prove
14
15. This reduction of drive signal
oscillator is operating.
Typical DC voltages for IC400 turned off the driver and output
are given in a block on the transistors so they drew no current.
Of course, loss of the drive signal
schematic. Keep them handy for
eliminates the high voltage and the
reference during troubleshooting.
the horizontal oscillator. Again,
are necessary for correct phase
detection and horizontal locking.
The horizontal sawtooth can be
viewed at pin 7.
Horizontal oscillation
The last function of IC400 is to
furnish most of the components for
CSC
0
45D
-I (ww.
150
+650 V TO SCREENS
220KO
,,...047
pF
HORIZ OUTPUT
+112Vdo.
Ferrite
HORIZ OUTPUT
c'
T440
/''Ì
HORIZ DRIVER
a
0
O
25
TO
26
CONVERGE
27
1.68
V
+170V
SOURCE
Ferrite
A
I
-.5
oi
bead
bead
o
R
1.5
V
.---
Gf446
25u~50 V
)
1150
á HORIZ YOKE
.O1
C448
1200 V
CR449-
'M
pF
CSC448)
Ferrite
270
TO
HV TRI PLER
S2
DAMPER
bead
Ì000Ìf
FLYBACK TUNING
6
7
á
560 pF
8'2"
R4q4
1300
CSC 530)
TO
+29 V SOURCE
CONVERGE
TO BLACK CLAMP CIRCUIT
+112 V
horizontal -oscillator functions are inside
Many of the components for the noise -inversion, sync -separation, and
circuit was described in the September
-down
The
shut
the
pins.
at
viewed
be
IC400; however, the vital waveforms can
is not grounded, but drives one winding of the flyback
of
0402
emitter
the
that
Notice
SERVICING.
ELECTRONIC
of
issue
Fig.
i
transformer.
www.americanradiohistory.com
New
B&K-
1
10MHz
Dual -Trace
Scope
Triggers to
20MHz
0101..
raster, so one of your first tests
when you encounter those symptoms is to measure the frequency
and amplitude of the square waves
at pin 15.
Horizontal Driver
From pin 15 of IC400, the square
waves go through R440 and C438
to the base of Q400, the horizontal driver transistor. No DC bias is
provided for the base; therefore,
loss of the square waves there
merely cuts off all the collector
current of Q400.
In normal operation, each positive peak of the square waves acts
as a temporary forward bias of
Q400, causing it to draw heavy
current during those peaks, and no
current between the peaks.
Q400 is an intermediate -power
type of silicon transistor, operating
with a collector voltage of about
+70 volts, and it does run warm.
R442, C442, and diode SC442, in
the collector circuit, are necessary
to shape the waveform which is sent
to the base of the horizontal -output
transistor.
When you are checking this
driver stage, your best tests will
invoí - the DC voltages and waveforms at the base and the collector.
quency. This is done for two reasons. It gives better high -voltage
regulation, and the amplitude of
the flyback pulse is reduced, thus
minimizing the possibility of damage to the output transistor. (The
waveform at the emitter of Q402,
the output transistor, changes
slightly as the "flyback tuning" coil
is adjusted. But the change is not
sufficient to use as a symptom.)
With Philco E20 and E21 chassis, the tuning is adjustable by
means of L400 coil, which is
labeled "flyback tuning". The
method of adjusting is simple: turn
down the brightness until the raster
goes black, then adjust L400 for
minimum high voltage. That's all.
Black -clamp
The
black -clamping
circuit
(called Automatic -Brightness Limit -
.
B&K-PRECISION
MODEL 1471B $495
Typical response is less than 6dB
down at 15MHz and usable
response is much greater.
5" CRT with bright P31 blue
phosphor
Mode automatically shifts
between CHOP and ALTERNATE
as you change sweep time for
fast set-up.
Fully regulated high- and lowvoltage supplies, for accuracy
over 105-130VAC range.
18 calibrated sweeps-1µS/cm
to .5S/cm
10 mV/cm sensitivity
TV sync separators
Front panel X -Y vectorscope
operation
Plug-in PC board construction
TTL compatible Z-axis
Available from your distributor.
g'KPREcIsIory
PRODUCTS OF DYNASCAN
6460 West Cortland Avenue
Chicago, Illinois 60635 312/889-9087
In
32
Canada: Atlas Electronics, Toronto
For More
Horizontal -Output Stage
It is interesting to note that the
collector of Q400 is the last point
where the drive can be viewed (if
the set is working properly). That's
because the output transistor,
rip,"
Q402, is floated high above ground.
Both the collector and the emitter
feed separate windings of the flyback; therefore, a scope connected
to the base or the emitter has the
same 420 -volt PP signal of negative going pulses, while the collector has
positive -going pulses of the same
amplitude.
Both the damper diode (SC448)
and the yoke with its capacitor,
C452, are paralleled across the C/E
terminals of Q402, in the conventional way. C448 has a major effect
on the amount of high voltage, and
you should not substitute any other
size for the .01 value.
Flyback tuning
In many solid-state television receivers, the horizontal -output stage
(yoke and flyback) is tuned to the
third harmonic of the sweep fre-
Details Circle (9) on Reply Card
Here are typical waveforms from the
IC400 and Q400 stages. The dual trace 10 -volt PP video waveforms
are (at the top) pin 4 of IC400, and pin
5 (at bottom). Top trace of the three
shows the 3.9 -volt PP positive -going
pulses at IC400 pin 7. These are inverted and integrated into 1.7-volt PP
sawteeth (center trace) for the phase
detector (the sync pulses do not leave
the IC). The square waves at the
bottom are the oscillator -output signal
at pin 15 (10 -volts PP).
ELECTRONIC SERVICING
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"try
you
de-
gree of color most pleasing to you.
NOTE: The NU -COLOR Picture Tube Restorer is not a "cure-all." Its function relates
only to the color correction of the TV Picture Tube. If faulty color, etc. is due to other
components in the set the NU -COLOR Restorer will not solve the problem.
© 1976, Oneida Electronic
Mfg., Inc., Meadville, Pa. U.S.A.
Printed in U.S.A.
aida
LIBMILLIOg
MANUFACTURING COMPANY, INC.
MEADVILLE, PENNSYLVANIA 16335
P.O. BOX 678
www.americanradiohistory.com
TELEPHONE 814 336.2125
Can another
portable OMM
measure up to
our popular
280?
Top trace of the square waves is the 4 -volt PP base waveform
of Q400, the driver
transistor. The 130 -volt PP collector waveform is shown by the
trace at the
bottom. Referring to the pulses, the top ones are the 400 -volt PP pulses
at the
collector of Q402, the horizontal -output transistor, while the
bottom trace
shows the 400 -volt PP negative -going pulses at the emitter (and
base),
measured relative to ground. Be careful when you test around
this area; all
three terminals of Q402 have strong horizontal pulses.
er or ABL in other brands) monitors the HV current that passes
through the flyback winding to the
HVT401 tripler rectifier (see Figure
2).
Before you can understand the
operation, you must remember the
rule -of-thumb about rectifier circuits: Any DC voltage coming from
rectification will be positive if it is
taken from the cathode of the
diode, or negative if it comes from
the anode of the diode. Look at the
tripler diagram in Figure 2; the last
diode feeds the picture tube from
its cathode. Therefore, the voltage
is positive. At the other end of the
tripler, the input AC goes to the
anode of the first diode.
Now, if you could measure the
DC voltage there (that's virtually
impossible because of the high amplitude pulses), you would find a
negative voltage whenever the picture tube draws HV current. Similarly, if you added a resistor from
the low end of the HV winding of
the flyback (terminal 10, in this
case) to ground, you could easily
measure a negative voltage from the
cold end of the winding to ground
(across the resistor).
Well, that's essentially how the
circuit operates, except the voltage
is positive (because R996 goes to
B+, not ground), and it becomes
less positive (negative -going) when
the HV current increases. This
control voltage from terminal 10,
C996, and SC996 acts to reduce the
positive voltages at the bases of
Q900 and Q902. Indirectly, the
November, 1976
brightness control also changes the
base voltages, so the action of the
black -clamp circuit is to reduce the
brightness of the picture when it
tends to become excessively bright,
regardless of the reason for the
extra brightness. These changes of
base voltages go down through the
video stages, changing the operating points of each stage until the
cathodes of the picture tube are
reached. And there the black -clamp
action raises the positive voltage at
the CRT cathodes to decrease the
brightness, and avoid overloading
the sweep system and the picture
tube.
You be
?? 280
Case Histories
Here are some actual repairs that
illustrate service procedures for the
horizontal sweep of the Philco E20
and E21 chassis.
Case #1
The original symptoms are no raster and no -sound. Removing the
shut -down SCR might bring back
the operation. But usually output of
the horizontal oscillator is lost some
time later.
Voltage checks of IC400 show
+17 volts at pin 14 (instead of the
usual +3.3 volts). A new IC does
not help. After many tests, we find
C416 has excessive leakage.
This problem started happening
quite often, before the factory made
some corrections to prevent it.
Later -production sets' have the
capacitor mounted off of the printed board to prevent heat damage
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PRODUCTS OF DYNASCAN
6460 West Cortland Avenue
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In Canada: Atlas Electronics, Toronto
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37
HV TRIPLER
HIGH
VOLTAGE
T400
FLYBACK
FOCUS
5.6 MQ
VOLTAGE
A14
10
GAP
10
t
luE
V
HORIZ
PULSE
Vv%
S
33K4
TO
DELAY
LINE AND
VIDEO
DRIVER
Q904
C42
BRIGHT
HORIZ
BLANKING
RANGE
FROM
NEGATIVE
NOISE
VIDEO
INVERTER
2 Details of the automatic -brightness limiter and the black -clamp circuits
are shown here. High -voltage current through the tripler to the picture tube
produces negative DC voltage at terminal 10 of T400, the flyback (increased
Fig.
current gives higher voltage). This negative voltage cancels part of the positive
voltage at the base of Q902. The circuit opposes any increase of brightness,
above the design point. Also, changes of video amplitude vary the collector
voltage of 0900, the black -clamp transistor, and the voltage goes through
SC916 and R916 to the base of Q902, where it maintains the correct black level
(brightness versus contrast).
during the time the board is in the
solder flow bath.
Use only an exact replacement
capacitor. If you substitute a standard .0033 capacitor, the chances
are good the irate customer will be
on the phone the first thing next
morning after he gets the set back.
Since there is no customer hold
control, the customer can't chase
the wandering horizontal frequency
as the capacitor drifts.
Case #2
This E21-04 chassis set came in
with a complaint of "no horizontal
locking". Replacement of IC400
A
B
Some Q902 waveforms are different because of the horizontal blanking that's
added there. (A) Top trace shows the emitter waveform with video and
horizontal blanking pulses; the pulses at the anode of SC924 are shown by the
bottom trace. (B) Top waveform is the conventional composite video signal at
the base of 0902; while the bottom trace shows the broadened blanking area of
the collector waveform.
made no change, and normal video
was found at pin 5 of the IC.
When testpoint "SS" was
grounded, the oscillator could be
adjusted for a floating picture of
the correct frequency, but removing
the ground caused the picture to go
farther out of lock.
Obviously, the defect was in the
ELECTRONIC SERVICING
38
www.americanradiohistory.com
phase detector. Pulses from the
blanker at pin 8 were 3.6 VPP,
which is about 10% low, but not
alarming. DC voltages at the video
input (pin 5) and the phase detector reference (pin 8) were
slightly high. Pin 8 was 2.4 volts
instead of the normal 1.6. These
voltage discrepancies were not
enough to upset a technician who
still thinks in "tube" language.
Perhaps the defect was in the
string of capacitors and resistors
around pins 7, 9, and 11. But
testing them involves a lot of unsoldering. So, back to the scope
again. At pin 8 the waveform was
wrong. The base had a lot of
"grass". In fact, half of the pulse
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connected one end of the diode, the
locking improved. A new diode
cured the problem.
(Continued on page 66)
steel ring -bound
the same system described
above, only reduced to
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tech's guide
was video!
How could video get into horizontal pulses? However, the pulses
do not come from the flyback, but
from the blanker transistor. Checking the schematic, I found a diode,
SC924, between the emitter of the
blanker and the emitter of video
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,1
SERVICING
ELECTRONIC
ORGANS
Part 6/By Norman H. Crowhurst
intervals.
Most modern organs have very little frequency drift, and do not require tuning at regular
types of
all
tune
how
to
know
need
to
will
you
But, if you repair old ones as well as new models,
for
the one
necessary
retuning
a
make
organs. And, of course, certain component replacements
explained
are
beats
audible
the
from
"fifths"
by
note that is affected. Two methods of tuning
thoroughly.
Tuning Electronic Organs
Many of the new organs do not
require tuning in the traditional
way. So. as the older organs
become obsolete and disappear, the
need for tuning methods or tuning
machines will be gone, also.
However, with the mix of brands
and models at present, the tuning
of organs is a necessary part of
servicing them.
There are several methods of
setting the "temperament" of the
notes near the center of the keyboard, without any equipment other
than a tuning fork for one note,
plus a timing device (stop watch,
etc). Two such methods will be described.
I advise you to try these methods
until you become proficient with
them. When you first start tuning,
probably you will take so much
time that each tuning will show a
loss instead of a profit. Of course,
you should gain speed with practice
until tuning jobs become profitable.
However, I must say that both
methods require close attention and
careful listening. In other words,
they are tiring and time-consuming.
Therefore, when your number of
tunings per year increases, you will
save both money and strain by
buying some kind of a strobe
tuning device, One such machine,
the Conn Strobotuner, was decrriheri in the May. 1976 issue of
ELECTRONIC SERVICING, starting on page 12.
The exact method of tuning an
organ depends on the basic design
and how many tuning adjustments
are provided. Some have one tuning
adjustment. many have 12, and
some have several dozens (even
several hundred, in a complex
model).
Single Master Oscillator
"space-age" models have
one master oscillator, which operates in the megahertz range. Some
oscillators are crystal controlled
(thus are not tunable), and others
have one frequency adjustment.
From this one oscillator, the countdown circuits produce the 12 tempNew
ered semi -tones. Next, from the 12
semi -tones, the lower octaves are
obtained by some kind of frequency
dividers.
If the master oscillator can be
adjusted, you can tune the whole
organ to any reasonable pitch
(concert pitch, or any other that's
desired) merely by turning one
adjustment. An organ that is not
defective moves all notes up or
down in perfect step with the variations of the master oscillator frequency. Therefore, you can zero beat any note against a standard to
tune the entire organ. Obviously,
the elaborate and traditional tuning
procedure is not needed here!
Following the tuning (or a checl
of the tuning), try all the notes of
the keyboards. If any note (or
notes) is out of tune with the
others, the problem is not tuning,
but a defect in the count -down or
divider circuits, which must be re
paired.
Twelve Master Oscillators
12 identical
circuit boards, each with one tuning
Organs that have
adjustment, undoubtedly are of
the master-oscillator/divider type
Those 12 adjustments tune the er
tire organ. One tunes all the "C's",
the next all the "B's", and so forth.
A few models have more than
one set of generators; for example,
a second set tuned slightly sharp or
flat to give a "celeste" effect from
the beats produced relative to the
main generator. In such cases, each
additional generator will have 12
tuning adjustments.
When all the dividers are operating correctly, you can tune any 12
consecutive notes (all sharps and
naturals) and the entire organ will
be in tune. Of course, tuning is
useless when one or more notes are
silent, play an octave high. or have
a gurgle. Make certain all notes are
playing correctly before you tune an
organ.
All Notes Tuned
An organ with rows and rows of
tuning adjustments probably is
ELECTRONIC SERVICING
40
www.americanradiohistory.com
lUI:
--_.--_
I
l
TUNING STEPS
MIMI
I
E-4
f-4
G-4
A-4
5-4
_
_
12
-
lo--'-.
7
-..
D-4
º-
--
e_-
III
C-5
D-5
`\
E-5
F-5
G-5
A-5
B-5
C-6
-
MIDDLE
C
i
"all -master -oscillators" type. In
other words, each note can be
tuned independently of all others.
That sounds like a lot of hard
work, but actually it's not quite
that bad. After the temperament
has been set near the center of the
keyboard, you can tune both up
and down from there by octaves.
Tuning by octaves is easy.
a
Setting The Temperament
If the natural tuning scale were
in use, you could start with one
note tuned to a standard pitch,
then sound the musical "fifth"
above it, and tune for a zero beat.
Actually, the zero beat is not between the two fundamentals, but is
between the third harmonic of the
first note and the second harmonic
of the fifth. But in practice, the
"equally -tempered" scale is used
instead of the natural, and with the
tempered scale, the fifth must be
tuned slightly flat. This is done by
counting the audible "beats".
Beats
The word "beats" is short for
beat -frequency, and it is exactly the
same thing in music as it is with
electronics: two frequencies together
in a non-linear circuit produce
sum -and -difference frequencies.
In music, the non-linear element
your human ears. And the sum
frequency is too high to be noticed
is
by most ears. But audio tones are
low frequency; therefore, the difference beat between them is very
low frequency.
What's more, the beat between
the harmonics can be even lower in
frequency; as low as one beat in
several seconds.
You must train your ear to listen
for these beats. First, tune the
second note and listen for the beat
to go faster or slower. This change
of speed will help you notice the
beat. A fast beat is a continuous
audio tone.
As the two frequencies are moved
apart, the frequency of the beat
increases (higher pitch); and that is
true regardless of which one moves.
Conversely, the nearer you adjust
the second frequency to the fixed
one, the slower the beat, until at
"zero beat" there is no beat at all.
A slow beat might sound like:
"a-wah, a-wah". After you have
heard these beats, you will not
forget the sound.
Fig.
Both the start and finish of
this tuning method are at "A" above
middle "C" (that's A-4 in universal
notation). The straight lines going to
the right represent tuning the higher
octave to zero beat. Some of the
1
lines that slant down to the left
show two separate tuning steps. For
example, the one near the top with
"A -51D-5" instructs you to play
those two notes while you adjust the
lower one (D-5) to obtain 10 beats
(on the high side of zero beat) during
5 seconds. Then, continuing on the
same line, you play "D-5" and "G-4"
while adjusting "G-4" for 7 beats on
the high side during 5 seconds. And
so on through the chart, until you
reach "E-5", which is played with the
original "A-4" to see if 7 beats are
obtained. If not, the sequence must
be done over.
number of' beats in five seconds,
and the second one requires you to
time the number of' seconds for 10
beats.
Counting Beats
Usually, an organ should be
tuned to "concert" pitch, which is
440 Hz for middle "A". A tuning
fork is the most inexpensive true
standard, and you should invest in
an "A-440" fork.
Prepare the organ by running it
for several minutes, turning off the
vibrato, and selecting one 8' stop,
perhaps a flute or diapason. It's
difficult to manage a tuning fork
and play a note, so block the note
down. Wedge the plastic blade of a
screwdriver or an alignment tool
between middle "A" and the next
note, then push down on the "A"
as you pull up on the other note
until "A" is the only note sounding,
and it stays down without any
attention from you.
Next, strike one tine of the
tuning fork on a piece of wood
Temperament is the same
(these forks are strong, but don't
Regardless of whether the organ overdo it), and quickly touch the
has 12 tuning adjustments or 176, fork handle to a flat surface.
the method of setting the tuning Without this contact, which makes
(temperament) is the same. It's the surface act as a sounding
done near the center of the key- board, the fork tone will be too
board.
weak to be heard.
I
will explain two different
Slowly, tune the "A-440" organ
methods of setting the tempera- note and listen for the beat note.
ment. The first one counts the Strike the fork as often as necessary
November, 1976
41
www.americanradiohistory.com
You
t=NCCF=t
CAN BE
SURE
MORE TIMES IN
MORE CIRCUITS
WITH SENCORE
DIGITAL
MULTIMETERS
to keep the tone loud. Turn the
tuning in the direction to make the
beat sound slower, until finally
there
is no
beat (that's zero -beat).
Tuning fifths
As shown in Figure 1, we now
jump back and forth across the
middle octave, tuning for a flatted
fifth. Actually, we are tuning the
root note, rather than the fifth, so
the root note must be tuned sharp.
That's why the sequence calls for a
certain number of beats on the high
side.
Remember, we will be counting
the number of beats in five seconds,
on the high side of zero beat. I'll
explain what that means. The beats
become faster on either side of zero
beat, but for this method the
phrase "high side of zero beat"
means the note you are tuning
should be on the sharp (higher
frequency) side of zero beat. You
can hear the note as it goes sharp.
Here is the sequence:
Starting with middle "A" (that's
A-4 according to universal notation)
tuned to the standard, tune the
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LESS CIRCUIT LOADING to make
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BONE THIRD
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10 megohm.
2000 DCV range to make you sure that you can
2imeasure TV boost volts, scope voltages, medical
equipment, etc. Other digitals stop at 1000 volts.
High voltage probe extends measuring capabilities to
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"A" one octave above (A-5) for zero
beat;
Using this "A" as the new
standard, play it and the "D" next
below (D-5). While listening for the
beat, tune the "D" to zero beat,
then sharp for 10 beats in 5
seconds;
Next, using the "D" as a standard, play it and the "G" below
(G-4), adjusting the "G" for 7 beats
per 5 seconds;
Zero beat "G-4" with the "G"
one octave higher (G-5), then play
"G-5" with the next lower "C"
(C-5), adjusting "C" for 9 beats on
the high side;
Using this "C" as a standard,
tune the "C" two octaves above
middle "C" (C-6) for perfect zero
beat;
Play this new "C" with the next
"F" below (F-5), and adjust the
"F" for 12 beats;
Play the same "F" with the next
lower "A#" (A#-4), and adjust the
"A#" for 8 beats;
Adjust the "A#" one octave above
(A#-5) for perfect zero beat;
Play "A#-5" with the "D#" lower
(D#-5), adjusting the "D#" for 10
beats;
Play this "D#" with the next
lower "G#" (G#-4), and adjust the
"G#" for 7 beats;
Use the "G#-4" to tune "G#-5",
an octave higher, to zero beat;
Play "G#-5" with the next lower
"C" (C#-5), tuning the "C#" for 9
beats;
Play the "C#" with the "F#" next
below (F11-4) for 6 beats;
Using the "F#" for a standard,
tune the next higher "F#" (F#-5)
for zero beat;
Play the "F#-5" with the next
lower "B", tuning for 8 beats;
Tune the previous "B-4" for zero
beat with "B-5", one octave above;
Play "B-5" with the next lower
"E", tuning the "E-5" for 11 beats;
Play "E-5" with the next lower
"A", and count the number of
beats for 5 seconds. If every tuning
step has been done perfectly, there
should be 7 beats.
This "A-4" is the one used to
start the tuning sequence, so it
should NOT be adjusted to make 7
beats. However, it might have
ELECTRONIC SERVICING
42
www.americanradiohistory.com
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drifted during the time you were
tuning; therefore, you should check
it again with the original standard.
If the last test with the "E" and
lower "A" gave more than 8 beats
or less than 6 beats, you should
repeat the entire sequence for
better accuracy.
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BATTERY SAVING FEATURES WHEN INSTRUMENT IS NOT IN USE so you can be sure
that your meter will be ready the next time you
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Push the button on the probe on the
DVM35 and DVM36 and only then do you start drawing current from your battery. An automatic patented circuit does
the
same job for you automatically when you apply voltage
to the
DVM32. The DVM38 is AC operated.
u --#V-K,fL-mA..c
zoo
"àaü
on
(11) on Reply Card
Fine-tuning the 5 seconds
In the event your tuning sequence
consistently gives the wrong number
of beats at the end, perhaps the 5 second counting time is slightly
wrong.
The original "A" should not be
changed, so you can sound the final
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6V 150 mA
LAMP
Fig. 2 This 5 -second timer can be built easily, then you can fine-tune
it for
the precise time necessary for perfect tuning by the beats.
"A" and "E", then carefully tune
the "E", noticing which way (flat or
sharp) it must be tuned to achieve
the required 7 beats in 5 seconds,
on the low side of zero beat. Notice
that this count is on the opposite
side of zero beat, according to the
way it was done previously. That's
because we are tuning the other
note of the two. This is the true
fifth tuning, in which the fifth must
be flatted slightly.
Now, if the beat rate is on the low
side, but is too fast (say 11 beats), it
proves the other beats were not
quite fast enough. Shorten the
5 -second interval used for timing
the beats.
On the other hand, if the beats
are on the wrong side of zero (or
are on the right side, but not fast
enough), it proves the beats were all
slightly fast. In that case, lengthen
the 5 -second reference.
Home -Made Timer
Figure 2 shows the schematic of
a simple timer you can build. The
transistors can be almost any kind
November, 1976
43
www.americanradiohistory.com
must be near their correct freAs explained before, the
Figure 3. A lower section of the quencies.
the third harmonic
is
between
beat
are
beats
keyboard is used, so the
note and the second
lower
of
the
much slower.
of the higher note. Now,
Strike the two notes shown at harmonic
lower note (the one
the
suppose
each step of the chart, and time the
is so far out of
tuned)
being
10
for
number of seconds required
its
fourth harmonic
beats. The easiest way to do this is tolerance that
harmonic of
second
the
with
beats
with a stop watch; hit the "start"
beat note
The
one.
higher
the
button when you strike the two
although
same,
the
sound
would
button
notes, and press the "stop"
Also,
weaker.
be
would
volume
the
after the tenth beat.
more
is
it
fast,
is
too
Otherwise, the method is the if the beat
it is
when
identify
than
to
difficult
same as given for the other one.
slow.
You adjust the lower note (using
So, to save much time and
the higher one as a reference) to be
mistakes, you should test
on the high side (higher pitch than minimize
of the notes which
temperament
that for zero beat) by the correct the
for
tuning, and
used
be
will
beats.
number of seconds giving 10
touch-up any that are badly off frequency.
Tuning Tips
Alternate Tuning Method
This can be done by ear, if you
organ
of
systems
of
these
Both
Some organ and piano tuners
the ability to hear in your
have
notes
prefer another method of setting tuning demand that the two
mind the way a progression of notes
should sound when one octave is
played in sequence. Add to the
scale of notes a few selected chords,
and you can estimate whether or
not the tuning is accurate enough
for the tuning system to be started.
of NPN silicon, and the variable
control provides a timing cycle between 3'/2 and 7 seconds. This
range allows you to select the exact
time that gives you the most
accurate Rifling.
In operation, you depress the
spring -return pushbutton switch,
which starts the cycle and turns out
the lamp. At the end of the time,
the lamp lights. Since the indication
is visual, it does not interfere with
the counting of the beats, as a
audible signal would.
Calibrate the timer either with a
stop watch, or with the second
hand of a watch, then tine -tune the
control setting as necessary to make
the tuning procedure accurate.
the temperament, as shown in
30
\
_
_Mimi 34T
s
TUNING
STEPS
'
23
26
38
_
\
32
V
E
F
"
27
29
G
..
24--..
36
"
A
BC
D
E
F
MIDDLE
C
tuning for flatted "fifths"
Fig. 3 Here is the chart of an alternate method of
each step than for those
for
required
is
time
more
by using beats. However,
of seconds for 10
number
of the other method, because you must count the
20 seconds, and the
requires
beats
of
measurement
heats. The shortest
required for this
longest one takes 38 seconds. Because of the extra time
the building of
including
even
preferred,
is
one
other
the
method, probably
the timer.
Charging For Tuning
Probably you should establish
flat -rate charges for tuning. Set
one figure for the oscillator/divider
types with only 12 frequencies, and
another for the separate -oscillator
types.
Of course, if you are asked to do
from the
normal tuning procedure, the rate
should be adjusted accordingly.
And the price should not be
much different regardless of your
experience (or lack of it), and
whether or not you use a strobe
device to speed up the process. If
you take too long, it's likely your
problem is lack of experience, and
the extra time can be considered to
be the price you pay to become
trained.
On the other hand, if you use a
strobe -tuning device which allows
you to tune an organ very rapidly,
part of each tuning fee must cover
a pro -rated sum to pay for the
machine. So, the charges should be
about the same regardless of your
experience or equipment.
something different
ELECTRONIC SERVICING
44
Many if not most of the
MA7V installations are in
dire need of repairs and
updating. Before you can
hid on such work, you must
know where the system is,
and who to contact. Examples of direct-mail letters
are given, plus many suggestions for tests and repairs of ailing MATV systems.
Upgrading
MAN Systems
Ely
[fort Wolf, Vi,
e
President of Sales, Jerrold Ele, ironie
Just before one of the
space
flights, an astronaut was asked
what one thing worried him most.
He replied, "The fact that everything in this capsule was supplied
by the lowest bidder."
Master Antenna TV (MATV)
systems, too, usually are installed
by the lowest bidder. If the specifications were not tight, or the inspection not made carefully, an
s
letters printed. If you have the
money to hire the whole project,
check with your local Chamber of
Commerce or the telephone Yellow
Pages for a responsible firm which
specializes in direct mailings. Give
such a company a sample letter.
and it will handle the whole thing,
for a fee.
On the other hand, if you have
more time than money, make up
your own list from an apartment
guide (ask your Chamber of Commerce for a source); copy from the
Yellow Pages; or obtain a specialized list from Standard Rate and
Data Service (SRDS).
MATV system might not have
operated correctly when it was first
installed. In addition, defects can
occur, and the system can be
tampered with. All of these causes
add up to poor MATV performance, as any traveler can testify
about most hotel and motel sys- Sample letter
tems. Experience has shown that
As long as a system operates at
MATV performances in apartment all, most managers will procrastihouses, trailer -parks, and condo- nate. An added inducement
is
miniums often fall far short of the needed to get action now. Perhaps
best.
the most powerful pitch is to offer a
So, the need is there and you are "free" survey of the MATV system.
competent (or can become so with
Any answer to this offer allows
our help) to make repairs or you to analyze the performance and
revisions. But how do you obtain layout of the system, which is the
the names on the dotted lines of the first technical step.
contracts? First, there must be an
Figure shows one suggestion for
interest on the part of the owner or a simple sales letter. Remember the
manager for better reception. Next, rules of good advertising; start with
you need permission to make a an eye-catching headline, then add
survey. From that data, you submit just enough material to induce the
a bid. Lastly, if you sell the
reader to call or write you. After
contract, the work must be ac- the prospect contacts you is the
complished correctly.
time to go into details. Excessive
and complicated writing is likely to
Steps For Selling
make the reader toss the paper in
Direct -mail messages are your the wastebasket.
best marketing tools for obtaining
MATV upgrading business. If you Printing
restrict the mailing to hotels, moThe prospect's first impression of
tels, apartment houses, trailer you comes from the sales letter. So,
parks, and condominiums, the list don't risk a drab letter from your
is short enough that you can cover
office typewriter, with the center of
every one in your area, without the "E's" and "O's" filled with ink.
excessive cost.
Most areas have modern "instant" printing facilities for short
Mailing lists
runs at reasonable prices. Many
A complete mailing list is necessuch firms will set the message for
sary before you have any sales you. This is recommended, for it
1
makes possible the use of different
sizes of type and various styles of
lettering. All of' these things are
important in making a good impression and maintaining the
reader's interest so he finishes your
message.
The Survey
Because you are doing the technical survey of' the system performance at no -charge, you must limit
the amount of time spent to
perhaps 20 or 30 minutes (plus
transportation). However, this time
must be used efficiently; and that
means planning and preparedness
before the call.
A chart form, as shown in Figure
2, is essential for recording data
about signal strength and picture
quality of each individual channel.
Of course, an accurate, portable
Signal -Strength Meter (Figure 3) is
required for testing the levels, and
a small battery -operated TV receiver enables you to see the picture
quality.
Check the headend
Start with the signal at the
output of the headend amplifiers.
Check and record on the chart the
signal levels of both picture and
sound carriers of each active channel. And then, through a suitable
attenuator needed to prevent overloading the TV used for testing,
check the picture quality of all
channels, using the portable TV.
Next, check the outputs of any
Splitters at the headend. It isn't
necessary to record the sound and
picture levels of all channels. Just
measure the picture carriers of the
highest channel and lowest channel
carried by the system.
Quality at
a
TV
If at all possible, you should
check the visual quality of all
channels at a typical receiver, and
record your comments on a form.
November, 1976
Ir
r
49
Better TV equals Happier Tenants!
to be happy
Sharp, steady TV pictures can help your tenants or guests
ghosty,
hand,
other
On
the
facilities.
your
with
with life, and satisfied
dissatisfaction.
their
to
contribute
pictures
blurred
and
jumping,
your building is so
That's why the Master TV antenna system for
important to your long-range profits.
picture quality from your antenna system is imperfect, contact
After
for a no -charge, no -obligation checkout of your installation.
quotations
will
submit
equipment),
test
inspection (using precision
to improve on
any needed repairs, and for additional equipment
original performance.
If the
I
me
my
for
the
channels,
Also, we can install security cameras, or time-weather -music
free your mind of any
and provide yearly maintenance contracts to
possible repair expenses.
prompt action.
Call nie today, or return the enclosed reply card for
Cordially,
(your name and title)
(address, city, and zip)
(phone number)
when the letter is
(Note: the word "tenants" can be changed to "guests"
motels.)
sent to hotels and
A
B
Fig. 1 Here is a
suggestion (A) foR
to
letters
sales
Dear Mr. (your name):
Yes. would like to have more
I
information about the
master 1V antenna services you offer.
owners/managers of
Please call to discuss our antenna needs.
apartments, trailer
parks, and condominiums. If you
Please make
hotels, motels,
Change the wording,
remember to keep it
interesting and brief.
Make this first contact a "soft sell". (B)
shows a suggestion
for a reply card.
at
a
no -charge, no -obligation survey of the antenna system
(address, city, state, ZIP)
Signed
Phone
Company Name
Address
State
City
www.americanradiohistory.com
ZIP
It's very possible for the signal to
be fine at the head end, but be
unacceptable at the end of a cable
run.
Problems
If you spot a trouble with the
signal, you should take a few
minutes to localize the source. A
final, precise diagnosis is not necessary at this time, but it is helpful to
know which branch or amplifier
has the problem.
Estimates
After the survey is complete, it
should be easy to make an estimate. Actually, you should make
two estimates: one for the cost of
restoring the system to the original
performance; and the second for
making the system work right, that
is, better than it was originally.
For example, suppose the survey
showed that one trunk line was
dead because of a defective splitter.
The first estimate should include
the cost of a new splitter and labor.
However, the second estimate
might recommend replacing the old
headend amplifier with a new -type
solid-state unit, adding
a pre-
amplifier to boost a weak channel
ahead of the main amplifier, adding
a UHF channel, wiring in filters or
traps to minimize interference, or
adding a closed-circuit TV and
background music channel.
Make your proposals in writing,
attaching a copy of the survey
results as proof. But do NOT mail
these papers! Deliver them in
person, direct to the owner or
manager. That way, you can sense
the attitudes, and know when to
add technical data or present the
practical benefits of the technical
suggestions.
AC Hum. Hum appears on the
TV screen as one or two horizontal
dark bars, which usually move
slowly upward. One hum bar
indicates 60 -Hz hum from a leaky
tube or a defective half-wave power
supply; two bars indicate 120 -Hz
hum, which can originate only from
a full -wave power supply. If the
hum shows on all TV sets connected to the system, it's certain the
defect is in the MATV. Hum on
one TV only indicates a fault in
that TV.
Rolling Picture. If the rolling is
with only one channel, the cause
usually is sync compression in a
single -channel amplifier. Aging of
the components might have decreased the AGC action, thus
increasing the gain. Use the manufacturer's procedure for resetting
the AGC. Of course, if the amplifier is tube -powered or without
AGC, you might suggest a new
solid-state replacement.
Cross Modulation. Grainy pictures, perhaps with "windshield
wiper", indicate excessive gain in a
broadband amplifier. A maintenance man or tenant might have
reset the gain, or the amplifier
could have aged. Reset the levels,
and add filters or traps as required.
Ghosts. It's not unusual for a
tenant to compensate for a bad
tuner in his TV receiver by shorting
out the isolation in the tap -off. This
might help his picture, but it would
add ghosts to other sets on the
same trunkline. Another common
problem is caused when a landlord
or supervisor has added cable to
the line. If this is done without the
proper termination (75 -ohm non -
inductive resistor), standing waves
(which resemble ghosts on the
screen) are created.
Snow. If snow can be seen
throughout the entire system, suspect the amplifier first. Replace the
tubes, or substitute a higher -gain
modern solid-state amplifier. A
broken downlead between the antenna and amplifier, water in a
splitter or tap -off, or a new building which shields the signal path all
can cause snow.
Old Problems
After you have repaired all the
defects that were not present when
the system was new, the picture
quality still might be poor on some
channels. The following are some
common deficiencies.
Ghosts and smear
True ghosts are caused by multi path. That is, part of the station
signal goes direct to the receiving
antenna, while another part goes in
another direction, is reflected by
some object, and finally reaches the
antenna, but at a later time.
Because the CRT beam is traveling
to the right, this signal that arrived
later appears to the right of the
main one.
Misunderstandings arise, sometimes, about the distances involved
with ghosts. A mountain 5 miles to
the side makes a ghost that's
displaced about 8 inches to the
right of the main picture on the
screen of a 21 -inch receiver. A
ghost reflected from a watertower
400 feet behind the antenna would
be seen only 1/4 -inch to the right.
Such a "close" ghost would appear
Frequent MATV Troubles
In most cases, you must assume
MATV Survey
that the MATV system worked fairly well when it was first installed.
Otherwise, the contractor would
have had trouble collecting for it.
(Of course, there are exceptions,
where the installer was more glib
than skillful. This possibility must
be kept in mind.)
Therefore, you look primarily for
troubles that develop with the
passing of time. A knowledge of
typical defects helps to identify the
problems. Here are some possibilities:
Channel
Number
Picture
Carrier
Sound
Carrier
Level
Level
Picture
Quality
(etc.)
Fig.
2
Make up a survey sheet, such as this, for the level
data.
November, 1976
47
www.americanradiohistory.com
Five big reasons to buy the RCA test jig.
1, When you buy the RCA
10J106, you get a color TV
test jig complete with a 19 inch picture tube for servicing almost all TV consoles.
2. RCA's up-to-date line of
optional accessories permits
you to service sets of 45
different makes: tube, hybrid,
solid-state, or PIL types.
3. With its high -quality construction, built-in, high -voltsafe operating
without the
33kV
to
capability
limiters,
voltage
use of costly
subscripand a set-up data
tion service, the RCA 10J106
is designed to give you years
of dependable service.
age meter,
4. Unique with the 10J106
system are two front -panel
switches for quick changing
of yoke impedances for almost any type of tube or
solid-state set. These
switches eliminate the need
to plug in external transformers and impedance matching devices.
5. A built-in, high -voltage
meter, calibrated to 35kV,
together
adequate
in excess of 30kV.
as ringing, or perhaps as a smear.
Certain kinds of multiple, closely spaced ghosts are seen as a smear,
to
not as ghosts. They are difficult
they
analyze sometimes, because
are similar to the smear produced
amby a misaligned single -channel
plifier.
Fig. 3 A professional signal -strength
meter which can measure the amplitude of both picture and sound
garners of all VHF and UHF stations
is a necessity for upgrading MATV
systems
with
shielding and picture -tube
permit measuredesign,
ments to 33kV without danger
from x-ray radiation. Allows
you to service all of the bigger
chassis that normally operate
These are only a few features
of the high -quality RCA
10J106 Color TV Test Jig. For
details and price information,
see your RCA Distributor. Or
contact RCA Distributor and
Special Products Division,
Deptford, N.J. 08096, attn:
Sales Promotion Services.
must experiment to find a
distance that cancels the ghost.
Aim both antennas directly at the
transmitting tower. Watch the picture on a TV set while you move
the two antennas closer or farther
apart. The spacing is right when
the ghost is minimized.
Multiple ghosts in one leg of a
system could be caused by a partial
short that changed the loading. A
short caused by a single strand of
loose cable shielding at a connector
will do it. Also, a loose connector, a
nicked or broken center conductor,
or an open circuit has the same
effect. One way of finding the
section with the short or open is to
insert a 6 -dB loss pad into one line
at a time. The attenuator improves
the match of one line and isolates
any short from the others. So, when
the attenuator pad improves the
quality, it's likely a defect is
position, height, and directional picture
that
section of the cable.
in
it
orientation for them. Sometimes,
Some MATV systems have 300 anidentical
two
helps to stack
ohm outputs inside the wall tap tennas horizontally (side -by -side); offs. This eliminates a matching
this cancels the signal at certain transformer at the TV, but it leaves
angles. The cancellation depends on a length of unshielded twin -lead
the distance between the antennas,
mismatched coaxial cable (perhaps from a crushed cable, or a
missing termination resistance) produces ghosts from standing waves,
where the signal bounces from one
end of the cable to the other, and
ith each bounce adding a ghost.
Incidentally, this is the same effect
as a defective delay line (or wrong
delay -line load) in a color receiver.
MATV systems slow down the
passage of the signals; therefore,
any pickup of signal that does not
travel through the system shows as
a ghost to the left. If the cable path
is less than about 200 feet, the
ghosts from the direct signal will be
seen as a smear.
The solution to the problem of
ghosts coming through the antenna
is to obtain antennas with a narrow
forward lobe and weak side and
rear lobes. Then, find the best
A
so you
ELECTRONIC SERVICING
48
www.americanradiohistory.com
... And, here are 50 more!
r
1
$50 worth of
$50
10J1Ó6 Test Jig Accessories FREE
When you buy the RCA 10J106 Test Jig
now through December 31, 1976, you
can select, free, up to $50 worth of
adapters and extensions from the full line
of available accessories.
All you do is send the following to RCA
D&SP, P.O. Box 100, Deptford, N.J.
08096, attn: Customer Service/Order
Processing:
Original proof of purchase (receipt, invoice or statement)
which includes date of purchase, stock number of
Test Jig, and name of RCA Distributor.
Filled out Purchase Registration Card.
Order for your choice of free accessories
(not to exceed $50 at suggested resale
prices), which will be sent direct to you
by RCA.
To select your free accessories, check
the list included in the "Set-Up Index"
booklet which comes with the Test Jig
when you buy it, or consult with your
RCA Distributor on selection and prices.
This offer expires December 31,,1976. So
don't delay. Buy a 10J106 Test Jig soon.!
RC/1 Color TV Test Jig
between the wall and the TV with the TV carriers
and producing
receiver. The twin -lead can pick up various kinds
of beats. Usually, the
a signal (in strong -signal areas), radio carrier
must be
causing a leading ghost. Other than (high power or very near)very strong
for this to
changing to a coaxial cable system occur.
with a matching transformer at the
Or, radio signals of very high
TV, the only solution is to increase intensity can overload
a MATV
the signal strength at each tap -off, amplifier. The overload causes
non perhaps by a more powerful head - linearity, and the radio
signal
end amplifier.
modulates the TV signals.
Sometimes, you can identify the
Radio interference
offending signal by tuning the
Radio carriers of lower than signal -strength meter for maximum
50 MHz can enter a MATV system on the interfering
signal, and then
in two general ways. First, any har- listening with
earphones to hear
monics of the radio transmitter are what modulation is on
the carrier.
received the same as any other
A sub-channel/TV splitter added
signal of that frequency, mixing between the antenna
lead and the
first ahlplitier might help by reducing all frequencies below 54
MHz.
In some cases, filters or traps are
required. Remember, any traps or
filters must be inserted before the
first amplifier stage.
FM interference
FM interference most often appears as a herringbone pattern that
moves with the modulation.
Minimize FM interference by in-
serting either a single -frequency
trap or an FM band -rejection filter
before the first amplifier. The trap
provides much more attenuation,
but it must be adjusted for each
station, and it tends to drift.
Band -rejection filters give less attenuation, but do not drift. Therefore, use a band -rejection filter, if it
reduces the interference enough.
Electrical interference
AMPLIFIER
BROADBAND
UHF SOLID STATE
Fig.
4
New solid-state UHF broadband amplifiers, such
as this Jerrold Model
older MATV systems.
UA -421, allow adding UHF channels to
Arcs from power lines or inside
defective equipment cause electrical
interference which covers all frequencies, but is stronger at the low
frequencies. UHF reception seldom
November, 1976
49
www.americanradiohistory.com
them on and off as a test (the
bothered by such interference.
motor is very near, perhaps in your
a
on
appearance
Although the
own home).
deis
different,
often
screen
TV
Interfering noise that occurs in
pending on the source, generally the
cycles might be from some
regular
interference appears as many tiny
controlled by a thermostat.
machine
Sometimes
black dots or dashes.
air conditioners, and reFurnaces,
but
random,
are
specks
black
these
alothers are found together in hori- frigerators are possibilities,
make
don't
motors
those
zontal bars, which move up or though
noise unless there's a defect.
down slowly.
Arcs in the power lines or transcleanNoise pulses from vacuum
identify. The
ers, mixer, or other brush -type formers are hard to don't know
men
-company
motors usually are random, and the power
defect unless it
source can be identified by turning how to find the
is
burns up something or affects the
flow of power. Direction -finding
Frith portable radios is frustrating
because the noise follows the power
wires and radiates from every wire
and pole.
Ignition noise
Ignition noise from trucks and
autos looks very much the same as
some kinds of random power -line
noises. Sometimes the solution for
both ignition and power noises is to
increase the signal in the MATV
PARALOG PLUS
VHF ANTENNA
SHARPSHOOTER
UHF ANTENNA
ff
N>
CH. 26
CH. 2, 4, 5, 9
Fig. 5 Another way
of adding UHF to
FCO -320
systems
MATV
which are inefficient
on UHF frequencies
is to convert each
UHF channel to a
VHF channel, before
it's fed into the system.
UHFNHF MIXER
BROADBAND
VHF AMPLIFIER
UVC
UHF
TO
3455
--
VHF
CONVERTER
CH. 11
TO DISTRIBUTION
SYSTEM
LOBBY
CAMERA
Fig.
6
Closed-circuit
TV cameras can be
included by having
each one modulate a
"Uni -Mod". The output is a VHF channel which is added
to the other VHF
signals at the head end amplifier. Each
is
then
camera
tuned -in the same
as a conventional TV
SUPER VU -FINDER
UN -MODS
I
ALL CHANNEL ANTENNA
(Ch. 2, 5, 9, 14, 34)
TVC -501
TVC -501
ELEVATOR
CAMERA
BROADBAND
station.
4545
UHFNHF
AMPLIFIER
ELECTRONIC SERVICING
50
www.americanradiohistory.com
system so it overrides the noise.
Better antennas, perhaps with
vertical stacking, and higher -gain
amplifiers often help cover the
noise. 300 -ohm twin lead between
the tap -off and the TV should be
replaced by a shielded 75 -ohm
cable with matching transformer.
Of course, this solution is not
practical for an entire system, but
it's suggested where the noise
affects only a few TV's.
Converter interference
In many MATV systems, the
UHF channels are converted to the
frequencies of unused VHF channels. Signal losses in the coaxial
cable are reduced at VHF frequencies, so lower -gain VHF -only
amplifiers can be used. This can be
a substantial saving on a large
system.
The tradeoff is the possible
interference to other channels
caused by radiation from the local
oscillator in the UHF converter.
Although the best converters are
crystal -controlled, either kind can
cause problems. With crystal control, the interference is stable; and
with other oscillators, the interference pattern changes with the
drift.
It's very difficult to calculate all
of the possible beats from converters, but the test for interference
is easy: just unplug the power cable
to the converter (or each converter
in turn) and notice if the beat
pattern is missing.
A radiating converter can be
isolated by placing it in a separate
shielded housing. Sometimes, rebalancing the levels will eliminate
the interference; it's worth a try.
Modulators can cause beats in
the same way, and the cures are the
same.
Overload
Too much signal creates as many
problems as produced by too little,
because of overload. Of course,
overload bothers only active com-
ponents, such as preamplifiers,
amplifiers, and TV receivers.
Overload of single -channel amplifiers weakens the sync by compressing it. Often the largest symptom is critical vertical locking on
that one channel. Eliminate the
overload by adjusting the AGC,
reducing the gain setting, or adding
a loss pad at the input signal.
November, 1976
Broadband amplifiers produce
cross -modulation distortion when
overloaded. Strong channels modu-
late weaker ones, although the
symptoms vary according to the
severity of the overload. A slight
overload causes a small constantly changing beat pattern, or a kind of
grainy look. Strong overload shows
a "windshield wiper" pattern: the
modulating -station picture can be
seen behind the desired picture.
Less severe overload might appear
as a tiny beat pattern and a dark
vertical bar that moves slowly to
>R)ww
AUTOMATIC
STAPLE GUNS
CUT WIRE & CABLE
INSTALLATION COSTS
.
.
without cutting into insulation!
SAFE!
Grooved Guide positions wire for
proper staple envelopment! Grooved Driving
Blade stops staple at right depth of penetration
to prevent cutting into wire or cable insulation!
It's more difficult to eliminate
overload in broad -band amplifiers.
The most important remedy is to
balance carefully the levels of all
the channels, making sure one is
not dominant. Single -channel filters
or frequency splitters might be
Adding UHF or CCTV
UHF channels can be added to a
VHF MATV system by either of
two ways. If the splitters and
tap -offs can pass UHF, an all channel antenna and a UHF broad-
band amplifier is the best bet
(Figure 4).
But if the system is so old that
the cable, splitters, and tap -offs
give excessive UHF loss, it's better
to add a UHF antenna and converter, as shown in Figure 5.
Modern apartment buildings are
concerned about security of the
tenants, and a Closed -Circuit TV
(CCTV) camera placed in the lobby
and elevator can be installed without great expense. Add a Jerrold
UNI -MOD for each camera, and
feed the signals into the MATV
system (Figure 6).
Comments
Modern MATV equipment and
techniques now permit good -quality
TV signals in most locations. Many
systems are working poorly, and the
owners and managers only need
some reminders to have their
systems upgraded. That's where you
can make money and do them a
favor, too.
Make up your sales letters,
distribute them, and start making
your share of the MATV profits.
Now!
O
BELL,
TELEPHONE,
THERMOSTAT,
INTERCOM,
BURGLAR
ALARM
and other low
1
/
added before the amplifier. Or
separate yagi antennas with individual pads might be used in
extreme cases.
T-18-Fits wires up to
3/16" in diameter.
No.
one side.
1
voltage wiring.
Uses T-18
staples with 3/16" round crown
hí¡/
in 3/8" and 7/16" leg lengths.
rT-25-Fits wires up to
/4" in diameter.
...----
Same basic construction
and fastens same
wires as No. T-18.
Also used for
RADIANT
HEAT WIRE
Uses T-25 staples
with 1/4" round crown in 9/32
3/8", 7116" and 9/16" leg lengths
ti
No. T-37
NEW! Intermediate
-Fits wires and cables
5/16" in diameter.
up to
Same basic construction
as Nos. T-18 & T-25.
Also used for
CATV and
DRIVE RINGS in
stringing wires.
i
Uses T-37 staples
with 5/16" round crown in 3/8",
1/2" and 9/16" leg lengths.
No.
1-75-Fits wires and
1/2" in diameter.
up to
cables
RADIANT HEAT
CABLE,
OF CABLE,
WIRE CONDUIT
COPPER TUBING
or any non-metallic Sheathed cable.
Also used as
DRIVE RINGS
in stringing wires.
Uses T-75 staples with '/2"
flat crown in 9/16", 5/8"
and 7/8" leg lengths.
i,
PAROIS FASTENER COMr'ANy, INC.
271 Mayhill Street, Saddle Brook, N. J. 07663
For More Details Circle
(12) on Reply Card
51
1
In the GE 19YC2 chassis, the
vertical oscillator transistor is reverse
biased when power first is applied. The
base voltage arrives at once, but the
emitter voltage is delayed by the large
time -constant R/C circuit. When the
emitter positive voltage finally exceeds
the base positive voltage, 0610 has
forward bias, causing the collector to
conduct through resistor RB (actually the
next stage) and discharging C616 (shown
by SW1). Two other signals at the base
reduce the positive voltage (increasing
the forward bias). The sync signal fires
the oscillator ahead of time, for locking:
and the regenerative signal causes a
stronger collector current for a short
period of time before C616 is discharged
and conduction stops until the next
cycle.
Fig.
0610
PNP
SILICON
C)
1000 Q
+22V
AND
I
t
MQ
Senvìciflg GE Modular Color TV
Part 4/By Gill Grieshaber, CET
Power supplies o/. two polarities for the vertical sweep come .from rectification
the
of horizontal signals. Also analyzed are other unique features and circuits of
-TV.
color
portable
solid-state.
vertical sweep in the 19YC2 General Electric
Vertical Sweep Of GE 19YC2
Although the vertical -sweep circuit of the GE 19YC2 has some
superficial similarities to both the
Zenith and RCA circuits previously
examined in this series of articles,
there are some unique differences.
The YC2 has an oscillator circuit
using a PNP and an NPN transistor, without any feedback from a
later stage, and so does the 19EC45
Zenith circuit. Feedback from the
output stage is necessary in the
RCA C'I'C58 to make the single
PNP
NPN
SILICON
+22V
-
circuits
RC
OUTPUT
both interesting and
ponent, making a yoke -coupling
capacitor unnecessary.
1MQ
TIME CONSTANT
Vertical Oscillator
0605 acts as a switch to reduce the 0610 base voltage when 0610
the
collector current flows, thus increasing the Q610 current and depleting
a variation of a
charge in C616 more rapidly and completely. The circuit is
multivibrator. but the two transistors conduct at the same time in narrow pulses
of current, and not alternately as is conventional.
Fig.
is
formative.
This GE vertical output stage
has two NPN-polarity power transistors, thus an extra phase inverter -driver is required. Two power
supplies are furnished, one positive
and one negative, and the output
signal has practically no DC com-
in
AND
r
switch -transistor oscillate.
Both the RCA and the Zenith
employ complementary -symmetry
output stages with one PNP and
one NPN power transistor. However, the RCA has a single power
source and an output -coupling capacitor to the yoke. The Zenith uses
two power supplies to create a zero
DC output voltage, and it doesn't
require a capacitor to couple to the
yoke. Refer to the April, 1975 issue
for details of the Zenith circuit, and
to the December, 1975 issue of
ELEC'T'RONIC SERVICING for an
explanation of the RCA vertical
circuit. A comparison of the three
2
The vertical oscillator circuit is
very uncomplicated, operating with
one PNP and one NPN silicon
transistor. One result of this selection is that both transistors draw
current at the same time, in
ELECTRONIC SERVICING
52
www.americanradiohistory.com
I+
SYNC
21
+
1.8 VPP
3.8 V PP
3.99 VDC
PNPT
OSC
PG7-7
VDC/
+.91V
.17 VPP
.2 VDC
WAVESHAPING--
10K0
3300
C
B/Y
B
VPP
3.99
C
S2
VERT
íA%
NPN
.027
10KO
E
OSC
500KO
VPP
330K4
+32.6
V
(SCAN RECTIFIED)
1 VERT HOLD
M0
.47
VERT
PG7-11
1
NF
1
S2
+2.7 VDC
+22V-*
TO
Q620
SIZE
01 VDC
330
3
E
.11VPP
i
+17
820KS2
3 Voltages and waveforms have been added to the schematic of the oscillator and sawtooth-shaping stages. All three
transistors are direct coupled. The vertical -hold control changes the time constant in the emitter circuit of 0610. By the
way, the "vertical size" control changes the amplitude of the sawteeth because of the variation of time constant, and not
because of any change of DC voltage at the collector of Q615.
Fig.
contrast to a multivibrator which
has the transistors conducting alternately. Also, these two transistors
oscillate by themselves: they do not
require any feedback from a subsequent stage. Even though the
circuit is simple, it is easier to
understand when analyzed in two
Bias by time constant
supply voltage, the emitter positive
voltage finally rises above the base
positive voltage. The transistor now
has forward bias, and the emitter/
collector current flows to ground
through the collector load.
If there were no more to the
circuit, the emitter voltage would
stabilize. But with the next stage
added, a "snap" action (type of
regeneration) suddenly increases the
Figure 1 shows only the main
wiring of Q610, the PNP oscillator
forward bias, and the stronger
emitter/collector current discharges
transistor.
When DC power first is applied
to Q610, the transistor is cutoff by
a strong reverse bias. (Remember
that transistor bias is base -to emitter, and not base -to -ground.) A
voltage divider having a very short
time constant applies about +4
volts to the base. At first, the
emitter has zero voltage, because
the voltage must travel through
R614/R616 and charge C616 before
the emitter voltage can rise. And
until the emitter voltage becomes
more positive than the base positive
voltage, the B/E junction is reverse
biased (the base must be less
positive than the emitter for the
bias to be forward).
Finally, after a time determined
by the time constant of R614/R616
(about 1 megohm) and C616 (0.1
microfarad) versus the amount of
C616.
SW1 is not in the circuit, but was
shown to simulate the way Q610
E/C current discharges C616; and
the resistance RB actually is the
steps.
November, 1976
B/E resistance of the next transistor.
Regeneration
Adding a few more components
(Figure 2) increases the Q610
current, and shortens the time the
current flows. It does this by
decreasing the positive base voltage
(more forward bias), the extra
emitter current bleeds C616, and
the low emitter voltage is reversed
bias, which turns off the C/E
current of Q610.
Q605 is used as a switch, which
reduces the base voltage of Q610
when it conducts. Also, Q605 acts
as an emitter follower to couple the
pulse signal to the next stage.
Here is the sequence, after Q605
has been added:
At turn -on the base voltage of
Q610 rises immediately to about
+4 volts, but the emitter voltage
increases more slowly, because of
the RC circuit;
Therefore, at first there is no
Q610 conduction, but eventually
the emitter voltage rises above the
base voltage (forward bias), and
Q610 begins to draw C/E current;
The collector current of Q610
flows to ground through the B/E
junction of Q605;
This B/E current causes Q605 to
conduct C/E current, and the
collector obtains the required positive voltage from the base of Q610;
In turn, the Q605 collector
current reduces the positive base
voltage of Q610. This is a large
increase of forward bias (for a
PNP), and Q610 conducts much
more;
The large Q610 current comes
from the charge stored in C616,
and the charge rapidly is drained
until (when about one-third remains) the emitter drops below the
base voltage, removing the forward
bias and stopping the conduction.
Therefore, the Q610 current has the
waveshape of a very narrow pulse;
Discharge of C616 is through the
55
Y642
Y646
There
is
0640
0630
0635
0645
only
HEAT
SINK
one
2 -WAY
RADIO
HOME
STUDY
COURSE
C648
CENTERING
C649
HOLD
R649
R651
HEIGHT
exclusively devoted
C636
to professional FM radio equipment
R650
C650
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!
Fig.
4
Name
Address
Code
D
I
I
I
am a former MTI student.
am presently in the military.
am a veteran.
ra
MT/
Formerly
MOTOROLA
TRAINING INSTITUTE
Summerdale, PA 17093
(717) 732.3636
56
For More
Details Circle (23) on Reply Card
0605
0610
0615
0620
Many components on the EP93X103 GE vertical module are identified.
C/E path of Q610, base -to-emitter
of Q605, and R612 (the emitter
resistor of Q605), which is another
reason that C616 does not discharge to zero voltage; and
Vertical sync also is applied to
the base of Q610. It is negative going, and triggers conduction just
before the oscillation otherwise
would occur.
Therefore, this two -transistor oscillator circuit operates at 60 Hz
(determined by the sync and the
time constant of the components in
the emitter circuit of Q610, which
includes
Please send me more information.
0625
a
variable vertical -hold
integration is to say that Q615 acts
as a switch. Conduction of Q615
discharges C620 (notice the zero
line in the waveform, at the bottom
tip), then C620 starts the textbook
charging curve, which is interrupted
(before it reaches the rounded
non-linear portion) by the next
conduction of Q615, bringing the
voltage to zero again.
It is interesting to note that,
although the waveshape is a good
basic sawtooth, the current of Q615
remains a pulse shape.
Many of the components on the
vertical module are pointed out in
control). The output waveform is a Figure 4.
series of narrow, positive -going
Vertical Drivers And Outputs
pulses.
The remainder of the vertical sweep schematic (Figure 5) strongly
Sawtooth shaper
resembles that of many convenThe complete vertical -oscillator tional audio power amplifiers.
schematic is shown in Figure 3,
There is one major difference:
plus the waveshaping stage using feedback from the yoke current
Q615, along with the important improves the linearity automatiwaveforms.
cally, so no linearity control is
Positive -going vertical pulses necessary (Figure 6). Low end of the
(with the baseline at zero) are the yoke goes to ground through R642
sole forward bias of Q615, an NPN- on the module. Voltage developed
polarity silicon transistor.
across the resistor goes through
Of course, normally the collector C636 and R636 to the base of
signal would be amplified negative- Q625, the differential amplifier.
going pulses, because of phase
Operation of the two "differeninversion in Q615. But these pulses tial" amplifiers seems rather mysare integrated into sawteeth by terious, even with the waveforms,
R618/R620 and C620. Then, C622 and needs some explanations.
couples the sawteeth to the next
stage.
Differential amplifiers
A better way of describing the
Although Q620 and Q625 are
ELECTRONIC SERVICING
drawn to resemble a classic differential stage, the circuit is not
exactly a differential stage. Output
is taken from one collector only.
Perhaps we should view Q620 as
having two input signals, one to the
base (it appears amplified and
inverted at the collector), and
another to the emitter (this one
appears amplified at the collector,
but not inverted). Also, Q625 is an
emitter follower, with input at the
base, and the non -inverted output
taken from the emitter. This signal
is connected to the emitter of Q620,
where it is the second input signal.
In summary, the signal at the
base of Q620 appears phase inverted at the collector of Q620,
while the signal at the base of Q625
appears at the collector of Q620 not
phase inverted. The two signals
subtract from each other! If they
were identical, the output would be
zero.
But they are not identical. The
major difference is in the rise time,
and there are some differences of
amplitude and linearity, also.
Therefore, the signal at Q620's
collector has been pre -distorted to
cancel subsequent opposite distortion occurring later. That's why the
waveform is so different from the
sawteeth we would expect.
Figure 7 shows the actual Q620
input waveforms and the result of
subtracting in a scope by inverting
the base waveform and adding
them. The resulting waveform consisted of positive -going pulses, and
that's the waveform found at the
collector of Q620, except for the
tiny sawteeth between each pair of
pulses.
Output -drive waveforms
From the preceding, you probably conclude logically that the
output of Q630 driver should be
negative -going pulses (Q630 inverts
the polarity). Not so. You see, Q630
is a PNP, so the positive -going base
pulses are in the cutoff direction.
Therefore, most of the pulse amplitude is clipped, leaving amplified
sawteeth. However, the B/E conduction of the output transistors
leaks some of the yoke flyback
pulses and the "butterfly wings"
from the pincushion circuit. In fact,
the base signal of Q640, the NPN
output transistor, is virtually identical in waveform to that of the
sweep -output signal as its emitter.
CASTLE
Statement of Ownership, Management and Circulation, Act of August 12, 1970; Section 3685, Title 39,
United States Code.
Title of Publication: Electronic Servicing
Date of Filing: September 30, 1976
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Wyandotte St., Kansas City, Jackson County, Missouri 64105.
6. Names and addresses of publisher, editor, and
managing editor: Publisher, Robert E. Hertel, 1014
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Carl Babcoke, 1014 Wyandotte St., Kansas City,
Missouri 64105.
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1.
2.
Timesavers
for the Professional
signal circuit analyzing
Instruments
SUMER®
Modem USA.
Mork
V
Ask your electronic distributor for them
Average
No. Copies
Each Issue
During
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12 Months
A. Total No. Copies Printed
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Date
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after Printing
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run shown in A)
or wrile for more details.
(24) on Reply Card
APPLIANCE REPAIR BOOKS
written in easy-to-undebtand language by experts with rnua-
trahons a diagrams Acclaimed by instructors a proless,onals How lo diagnose 8 repair au conditioners refr,gerators.
1,102
609
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ROBERT E. HERTEL
I
Lists more than 2800 items pliers, tweezers,
wire strippers, vacuum systems, relay tools,
optical equipment, tool kits and cases. Also
ncludes ten pages of useful "Tool Tips" to aid
in tool selection.
JENSEN TOOLS AND ALLOYS
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57
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PERMIT NO. 8685
CLEVELAND, OHIO
POSTAGE WILL BE PAID BY:
CLEVELAND INSTITUTE OF ELECTRONICS, INC.
1776 East 17th Street
Cleveland, Ohio 44114
www.americanradiohistory.com
Non -symmetrical output
As I mentioned before,
the two
output transistors are alike, both of
NPN polarity, and not a PNP
balanced against a NPN as is done
in many models.
This means that the two bases
cannot be tied together by a diode,
as is true with the complementary symmetry circuits. Instead, a phase
inverter (Q635) must be provided.
The collector of Q635 is directly
connected to the base of Q645, the
NPN output, and the collector of
Q645, along with the emitter of
Q640, drives the yoke.
Notice that both Q635 and Q645
are connected for highest gain
(common -emitter type circuit; signal in at the base and out at the
collector), and yet together produce
a gain of approximately 1 (unity). I
will not attempt to explain this
phenomena; probably it's because
each transistor feeds an extremely
low impedance, and that always
reduces gain.
The arrow points to
the vertical -centering
control, at the side
and in front of the
vertical -hold control.
The height control is
to the left of the
hold control.
i
iiifi
tif
ft;ittiit
WIZ
MI MI RIM BUM
MIMI MI all MIMI IMO
NUM
UiMI
MI Ell MIii
IWO
IlB MI
MO OM MN
MIlMItiQi
1MI III Will
WIN
IMO 1111111181111111 OBI MI
IN MI
Fig. 6 When the height is reduced by the vertical size control, the linearity
continues to be excellent.
Centering
Normally, the two output transistors conduct the same, and because
they are fed from two separate
power supplies of opposite polarity,
the output signal to the yoke has
virtually no DC voltage or current.
Any unbalance between the two
transistors causes current to flow
through the yoke, thus changing
the vertical centering. Going back a
step, any shift of DC voltages in the
differential or driver stages upsets
the balance of output transistor
currents.
This balance (and the vertical
centering) can change because of
defective components, or it can
occur because of the "vertical
centering" circuit which deliberately varies the balance. The base
voltage of Q625 is adjustable
through R626, R634, and R660.
The picture can be moved about 1
inch up and down (Figure 8).
Horizontal -Sweep Rectification
One DC supply voltage from
outside the module feeds the vertical -size control. In addition, the
vertical module contains two other
power supplies that rectify different
polarities of horizontal pulses (Figure 9). Because the vertical power
comes from the horizontal, the
height does not increase when
Fig. 7 When the yoke -current waveform at the base of Q625 (top trace) is
subtracted from the drive sawteeth at
0615 (inverted to simulate the polarity
change in Q620, shown by center
trace), the result in the scope is
positive -going pulses and small saw teeth (bottom trace). That's nearly the
waveform obtained at the collector of
0620, produced by the action of the
"differential" transistors.
sass---s--s-ss-i
aa-isos-s
--111n-wares
----asas
-----s-
-s--sis-s---i
sisas
A
sssss011ss
1-s--nrr1111--
sss-11111111s
---is--ss-s
--s--s-s
-sis--s------------aa
B
Fig. 8 With the vertical -centering control turned to one end, the picture was
about 1/2 -inch too high (notice the center dot in photo A), and -1.25 volts was
measured at the yoke. At the'other extreme of the centering control, the yoke
had +1.5 volts, and the picture was about 3/4 -inch too low on the screen
(photo B).
excessive brightness causes blooming.
One surprise from the waveforms
was the large 60 Hz (actually 59.45
November, 1976
Hz) ripple present at the output of
both DC supplies. At first thought,
it seems impossible, because the
diodes are fed horizontal pulses,
61
www.americanradiohistory.com
.0022
+13.9
R67-3
140
V
V
SUPPLY TO
11,
PP
C642
1000 u F
OV DC
Q640
25 V
470 pF
.
Y642
RL7-2
Here are the circuits
and waveforms of the two
-12.5
1000
OV DC
11-1
9
V
SUPPLY
14
130VPP
Fig.
0022
{.1F
TO
Q645
25 V
power supplies for the
output transistors. The input waveforms were photographed at horizontal rate;
the output ripples at vertical rate, as explained in
the text.
and this should eliminate all 60 -Hz
ripple, regardless of the size of the
filter capacitors. The hum waveforms are created by the large
currents of the vertical -output transistors which are not bypassed completely by the 1,000 microfarad
filters (C649 and C648). In other
words, the "hum" is from the
vertical, not the AC line.
A
A
Open Output Transistors
In order to show the symptoms of
open Q640 or Q645 output
transistor, I removed one at a time,
and photographed the scope waveform and the crosshatch pattern
from the picture tube. The results
are shown in Figure 10. In addition
to the distinctive patterns, the DC
voltages were changed significantly.
When Q640, the transistor for
"bottom" deflection, was open, the
an
B
B
positive supply voltage was high,
and also the DC voltage at the yoke
was about -1 volt.
When the transistor for top
deflection (Q645) was removed, the
negative voltage supply was high,
and the yoke measured about +1
volt DC.
Even with such a huge amount of
C
C
Fig. 10. These three pairs of pictures show what happens when either output
transistor opens. (A) gives the normal crosshatch on the screen and the normal
scope waveform at the output of the module. An open Q640 produced the
crosshatch and waveform of (B), and -1 volt at the output. Evidently Q640 deflects the bottom of the raster. When 0645 was open, the crosshatch and
waveform of (C) were found; the yoke had +1 volt. 0645 deflects the top half
of the raster.
distortion, the small amount of
visible height had good linearity; a
tribute to the circuit design.
Incidentally, the output transistors and resistors on the module
were unusually difficult to remove
from the board. Even with all
solder removed, and the leads
ELECTRONIC SERVICING
62
www.americanradiohistory.com
they moved. These evidently obscured the usual sweep waveform,
so that the picture of the pattern at
vertical rate showed no resemblance
to the correct waveform.
11111111131111111111
limmuumun
minimmin
mammui
-um
Fig. 11 An open C636 gave these symptoms on raster and scope. This is one of
the few defects that can stretch the linearity. It removes the negative feedback.
wobbling like a loose tooth, the
wires could hardly be removed
without breaking them. Bends of
the leads at the board seems to be
the reason. Perhaps you can
straighten out the leads of any you
remove, and do it easier than I did.
Defects Causing Poor Linearity
Circuits such as these having
feedback from the yoke current are
almost immune to poor linearity
because of defective components.
But I did discover two interesting
symptoms involving the linearity.
Open loads
Strange crosshatch and scope
patterns, like none I have ever seen
before, were produced by open
circuits in some of the components
wired in parallel with the yoke
coils.
When R649 or R651 was removed, the raster scanning lines
were bent in curves near the center
of the screen, leaving two oval areas
without lines (Figure 12). Also,
R650 burned to a crisp.
After R650 was removed to
remove the heating, the open ovals
were reduced to just one located
slightly to the left of center.
No feedback
Excessive height and stretched
linearity at the top (see Figure 11)
were caused by an open C636, the
capacitor that couples the feedback
from the yoke to the differential
stage. Strangely enough, the "butterfly wings" from the pincushion
correction were missing from the
yoke waveform.
Probably the height could have
been reduced by lowering the
setting of the vertical size control,
but the linearity would have remained poor.
A
Comments
remember the problems we
had (and still do sometimes) with
the old tube -powered vertical circuits, I appreciate the new solidstate vertical systems. The tube
circuits commonly changed height
or linearity as they heated, they
might roll or flip unexpectedly for
no good reason, and often it was
nearly impossible to obtain both
full height and good linearity.
By comparison, the GE vertical
circuit was totally stable, never
rolled (except during a channel
change), and had perfect height
and linearity.
And yet I shudder a bit when
thinking of the weird and difficult -to -analyze voltages and symptoms that can happen when something upsets the DC voltages in the
differential, driver, or output stages
(all direct coupled).
As a test, I shorted base -to emitter of Q620. Of course, there
was no vertical sweep, but the
horizontal line was about 2 inches
from the top of the screen, and the
yoke measured -5 volts. Evidently
Q640 was biased to cutoff, and
Q645 was saturated. I chickened
out, and quickly shut off the power
to prevent ruining any transistors.
Perhaps later, I can strengthen my
courage enough to analyze some of
these massive failures.
As
However, when R650 or C650 were
opened while R649 and R651 were
in the circuit, no visible defect
could be seen on the crosshatch
pattern.
Two scope waveforms are shown;
one was at the horizontal rate, and
the other at vertical. Both show
unwanted movements, coming from
the pincushion action. The wave-
form taken at horizontal rate
should have shown nothing, but it
revealed strong horizontal -sweep
patterns. which were a cross between pulses and square waves, and
B
I
Next Month
Chroma and video circuits will be
spotlighted next month.
C
Fig. 12 An open R649 or R651 anti -ringing resistor produced these strange results. Unstable bending of the scanning
lines near the center (A) were slightly different with and without R650 in the circuit. Output to the yoke had this waveform
(B) when the scope was set for vertical rate; and the foreign areas of (B) proved to be horizontal signal when the scope
was set for horizontal rate (C).
November, 1976
63
www.americanradiohistory.com
uroductm
the Restorer for several hours to
achieve full correction.
These features 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.
Picture -Tube Restorer
different method of increasing
the gun current of weak color picture
tubes is incorporated into the NU COLOR Picture -Tube Restorer offered by Oneida. This unit does not
change the heater voltage, although
the physical appearance is similar to
those that do. Instead, three linear
controls adjust the amount of current
applied to some elements of the
picture tube. The color of the levers
identifies the correction of red, blue,
and green gun current.
The NU -COLOR Restorer is installed by plugging it in between the
base of the picture tube and the CRT
socket. Then, with the color control
turned down, the three sliding controls are adjusted for the best balance
giving a good black -and -white picture.
Afterwards, the color control can be
turned up for a pleasing picture.
Some picture tubes, according to the
manufacturer, require operation with
A
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64
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(34) on Reply Card
the older round color tubes, and
Model 90A is for the rectangular
tubes. Retail price of each is $24.95.
For More Details Circle
Want to get out from behind the 8 -Ball? Then
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(45) on Reply Card
Purchasing Guide
Allied Electronics' 1977 Engineering
Manual and Purchasing Guide now is
ready. The 212-page guide is filled
with a wide selection of industrial-
type electronic parts, components,
supplies, and equipment. Some items
featured are: test equipment, trimmers and potentiometers, transformers, tools, capacitors, new solar energy products, CB test equipment,
and even a microcomputer. Also, new
in this year's guide is the introduction
of metric measurements on many
electronic parts and components.
A copy of the guide can be obtained
by sending $1.00 to cover postage and
handling to: Allied Electronics, Dept.
77, 401 East 8th Street, Fort Worth,
Texas 76102.
For More Details Circle
8 -TRACK
of your car,
designed for
easy handling
and simple
Two versions are available; Model
70A with large plug and socket is for
(46) on Reply Card
FM Converter
Audiovox Corporation has expanded
its line of mini, under -dash units with
the introduction of a tiny FM con-
verter.
The gold-finished, micro -sized Model
FMC -4C converter measures 4" X
3-3/4" X 1". It has a black-out dial
with an LED station indicator, allsolid -state circuitry, and a push on/off
switch. It features a built-in "Tune
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PROJECTOR-RECORDER
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301 Whitewater St., Whitewater, WI 53190
(414) 473-2151
24 -Hour Answering Service
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www.americanradiohistory.com
Tone" which simplifies tuning to the
proper frequency. A tone is emitted
indicating the correct frequency for
FM tuning of AM radios.
(Continued on page 66,
ELECTRONIC SERVICING
bookií* rt
new phosphor pi7cture tube
with twice the brightness
CB Rules and Regulations
Author: Compiled By The Howard W. Sams
Editorial Staff
Publisher: Howard W. Sams & Co., Inc., 4300
West 62nd Street, Indianapolis, Indiana 46268
Size: 44 pages, book number 21341
Price: $1.00 paperback (Canadian Price slightly
higher)
The complete text of Part 95 of the FCC Rules
and Regulations is included, revised to reflect the
latest changes. It also contains copies of two
important FCC Forms: Form 505, Application for
Class C or D Station License in the Citizens
Radio Service; and Form 555-B, the Temporary
Permit. Complete instructions for completing
these forms are given in the book. In addition,
"10" signals and "Q" signals, the verbal
shorthand used by CBers, and a section on CB
slang are included in this guide.
Handbook Of Solid -State Troubleshooting
Author: Hershal Gardner
Publisher: Reston Publishing Company, Inc.,
Y.O. Box 547, Reston, Virginia 22090
Size: 318 pages
Price: $15.95 hardbound
State-of-the-art semiconductor troubleshooting is
emphasized, also the practical aspects of semiconductor devices, circuits, and systems, with
theory held to a minimum. Test and measurement techniques are explained and illustrated for
each individual subdivision of semiconductors.
The broad spectrum of topics includes device
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and test -equipment maintenance.
Contents: Solid-state Principles and Testing Procedures; Normal and Abnormal Voltages and
Waveforms; Troubleshooting Basic Solid-state
Amplifiers; Troubleshooting Solid-state Power
Supplies; Troubleshooting Solid-state Control
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and Stereo Receivers; Troubleshooting Solid-state
Quadriphonic Equipment; Troubleshooting Solid-
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double the brightness for bright
displays even in high speed dual -trace modes. Bandwidth: DC to 15 mhz. Unique features for the industry's
Automatic Triggering Automatic
greatest value are:
Astigmation Automatic Horizontal Sweep Automatic
Horiz/Vert. TV Triggering provides positive display on
composite video signals. Vertical sensitivity: .01
volts/cm to 20 volts/cm in 1-2-5 step sequence.
Horizontal Sweep Speeds: .2 sec/cm to .5µ sec/cm in
1-2-5 step sequence. Has 5X magnifier at all sweep
speeds. External Horiz. Amp. Bandwidth: DC to .5 mhz;
Sensitivity: .5 volts/cm. Calibrated Test Signal: 1 volt
P -P square wave. Power: 105-125 volts, 60 cycles, 65
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$489.50
Model TO -60 Less Probes. Net
P-31 phosphor CRT has
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is DC to 10 mhz.
Model TO -55 Less Probes. Net
$379.50
For the "bright one,"
see
your distributor, or write:
twII LECTROTEC
H, INC.
5810 N. Western Avenue, Chicago, Illinois 60659
Area (312) 769-6262
For More Details Circle
(36) on Reply Card
65
November. 1976
www.americanradiohistory.com
(Continued from page 64)
The compact converter installs easily with grip -tight mounting strips,
and uses a regular AM antenna. It
weighs 11 ounces, and has a tuning
range of 88-108 MHz.
Suggested list price of the Model
FMC -4C is $39.95.
For More Details Circle (47) on Reply Card
Removable Mount
For CB Antenna
"Hide -It", from RMS Electronics, is
a quick -disconnect trunk mount for
CB antennas. The trunk -lip half of the
mount is installed permanently in
place on the car. The other half of the
mount attaches to the antenna, so it
can be placed on the truck bracket for
radio operation, or removed by
loosening one screw when the antenna/mount assembly is to be hidden
inside the trunk as a protection
against theft or damage.
The mounting bracket fits most
Four affordable, deluxe
counters-one for every need.
MOD 0 M
1
Hz to
MODELM 380X.1
Hz to 80
Hz, 1ppm
MODEL 385.
1
Hz to 512 MHz, 10ppm
MODEL 385X.
1
Hz to 512 MHz, 1ppm
$269
$395
(48) on Reply Card
For More Details Circle
$499
MHz, and 10 Hz to 80 MHz.
Models 385, 385X feature a
built-in prescaler to take you
all the way to 512 MHz.
Models 380X, 385X incorporate
temperature compensated
crystal oscillators with 1 ppm
accuracy, auxiliary 1 MHz
timebase output. External
timebase inputs on Models
380, 385.
See these exciting new
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the value innovator
INSTRUMENTATION & CONTROLS DIVISION
THE HICKOK ELECTRICAL INSTRUMENT CO.
10514 Dupont Avenue Cleveland, Ohio 44108
TWX: 810-421-8286
(216) 541-8060
(37) on Reply Card
E21
Chassis
(Continued from page 39)
Case #3
The symptoms of 'this E21 pointed to power-supply problems, because the picture was shrunken on
all four sides. In the past, the
defect always was the filter C520,
which reduced the 140 volts to
about 100. Oops! The voltage was
140 volts; so it couldn't be C520.
Also, the +112 -volt supply was
okay.
Now, this is one of the worst
corners a technician can paint
himself into. Your preconceived
idea is proved all wrong, and you
are left with no other solution. The
solution is to go back to basics, and
stop the short-cuts. First, what
about other symptoms?
At loud volume, the vertical
would pull-up even more and the
width would change in step. The
supply voltages were normal, except
the 29 -volt line which was down
about 4 volts. Perhaps the vertical
was drawing too much current, and
loading-down the horizontal. That
was wrong, because the drop across
R532 (see last month) was only 0.3
volt.
Finally, I got around to measuring the high voltage, and I was
astounded to find 42 KV. WOW!
Waveforms around the output
transistor emitter showed a couple
of foreign curves that didn't belong.
And, finally, an ohmmeter test
from emitter to ground showed
4,000 ohms. (The emitter should go
to ground through a flyback winding of less than 1 ohm.) Yes, the
winding was open.
The symptoms finally began to
make sense. Lacking a return to
ground through the flyback winding, the emitter of Q402 sought the
next path through SC530 and the
transistors supplied by that power
supply.
I assumed the increase of high
voltage was due to a change of the
turns ratio of the flyback. Undoubtedly, the pulses were increased at the collector, and the
primary has one less winding, so
the voltage would be stepped -up
more at the secondary.
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Full 7 -digit display with
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each second to aid tuning
and adjustments.
Resolution is 1 Hz to 10
For More Details Circle
cars and accepts most CB antennas;
also, it secures the coaxial cable in
place and grounds it.
"Hide -It" Model CBTM-20 removable antenna mount is supplied with a
self -adhering rubber strip to protect
the finish of the car, and installation
D
instructions. List price is $11.95.
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The quick
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Drill.
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ORIGINATORS OF PRACTICAL CORDLESS SOLDERING
Sterling, Illinois 61081 (815) 625-6525
"Manufacturing Excel/Price
For More Details Circle
."u
Next Month
Vertical and chroma circuits, and
some typical problems there, are
the subjects for the next article.
nce 1919"
(38) on Reply Card
www.americanradiohistory.com
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SYLVANIA
Chassis E11-5/-61-7/-8/-13
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November, 1976
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Details Circle (42) on Reply Card
(39) on Reply Card
The
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The MARKETPLACE
EDUCATION -INSTRUCTION
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8-76-tf
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Minimum classified charge $3.00.
TV
For ads on which replies are
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HOW TO
HINTS-Repair your TV. Send make & model,
$2.00 + stamp. Charles TV, 2033 McGraw Ave.,
Bronx, N.Y. 10462.
11-76-1t
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costs.
without expensive advertising. Work pulling
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Classified columns are
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turers unless used
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8-76-tf
UNUSUAL SURPLUS AND PARTS Catalog. $1.
ETCO Electronics, Dept. E.S., Box 741, Montreal
"A" H3C 2V2.
7-76-101
INCREASE SERVICE PROFITS & Collect In
Advance. Service Contract Manual.
Practical
Home Electronics Service Business Manual. Each
Manual $12.50, both $22.00. NATESA, 5906 S.
Troy St., Chicago, II. 60629.
11-76-31
HELP WANTED
$19,000.00 PLUS per year for excellent outside man. Qualifications: Totally honest, industrious,
non-drinker, non-smoker. Prefer 15 years or more
experience. If lazy do not apply. Send resume to
American Television Service, 1032 South State,
Orem, Utah 84057.
10-76-2t
POTTER BRUMFIELD RELAYS: fc 11d-24, SL 7005 -28, 8 on Board. Unused-$20.00. CKT.
Board, Loaded, $1.00, 6/$5.00.
11-76 1t
-8
SAMS
to 466 (156 folders)-$125. Paul Ellis,
419 Bellevue St., Santa Cruz, Calif. 95060.
11-76-1t
FREE-Giant bargain electronic catalog, listing
thousands of components, tubes, transistors,
IC's, kits, test equipment. Edlie's, 2700 -EC,
Hempstead Tpke., Levittown, N.Y. 11756. 8-76-3t
BUSINESS OPPORTUNITY
location 15 years.
Retiring. Including truck,
equipment & inventory $25,000. A. Bolin, 6361
Balsam Lake. San Diego, Ca- 92119.
6.76-tf
TV SALES & SERVICE in same
Nets over
$25.000
TIRED OF CUSTOMER ABUSE? Expand into
lucrative patented MATV. Preliminaries $3.00.
Box 809, Boynton Beach, FL 33435.
10-76-6t
SERVICE-Established 15 yrs. 2
houses, shop on corner lot. Servicing over 500
motel sets, mostly color, very good volume,
drive-in service, good reputation. Inquire 305-2679570, Titusville, Florida. Will show figures to interested buyers only. 509 Park Ave., Titusville,
TV SALES &
Florida 32780.
11-76 1t
BUILD ELECTRONIC DEVICES in your home. Get
started in your spare time. Big profits. Experience not necessary. Ask for free literature telling
how. Electronic Development Lab, Box 1535,
Pinellas Park, Fla. 33565.
11-76 1t
TELEVISION SALES AND SERVICE BUSINESSCentral East Coast of Florida where its warm.
Zenith sales and service plus RCA and Sylvania
service work. Good established business. For
details call, George Lewis, Realtor, 305-784-1290,
3500 N. Atlantic Ave., Cocoa Beach, Fla. 32931.
11-76-
lt
SALE-TV SALES & SERVICE BUSINESS.
Zenith dealership, stocked TV's & parts. In the
beautiful Bitteroot Valley, clean air, mild winters,
recreation, fishing, hunting, skiing, in Gods
Country. Priced to sell. Retiring. PH. 406-7775111, John Mednansky, Stevensville, Mt.11-76- 1t
FOR
FOR SALE
TV SALES &
Chicago sub area. Zenith
tablished 1937. For info Mr.
ham Ave.. Calumet City, III.
68
advertisers' Ii»
SERVICE-Business
distributership-es-
Luberda, 646 Burn60409, 312-862-7274.
11-76 1t
SAMS PHOTOFACTS-approx. 485 sets, starts at
2. Solid 1044 to 1231. $485.00 for the lot.
Sencore SM152 sweep & marker with book and
cables $100.00. Sencore CR143 CRT tester with
book and cables $50.00. Royce's Electronics,
P.O. Box 1267, Moab, Ut. 84532, Ph: 801/2596630.
11-76
It
KIT Postmarker Sweepgenerator. Mint
condition with cables and attenuator. $195.00.
David Tully, 586 Buttonwoods, Warwick, R.I.
02886.
11-76 1t
HEATH
PICTURE TUBE MACHINE-We buy and sell
NEW and USED CRT rebuilding machinery.
COMPLETE TRAINING. Buy with CONFIDENCE
from the ORIGINAL MFGR. For complete details,
send name, address and zip code to: LAKESIDE
INDUSTRIES, 3520 W. Fullerton Ave., Chicago,
III. 60647, Phone: 312-342-3399.
11-76 1t
WANTED
NEEDED: 2EP4 Picture Tube for Philco TV,
Model H2010. Larry Auman TV, Rt. 1, Box 368,
Dover, Ohio 44622.
11-76-1t
Lees keep
Scouting
going
stronger
than ever.
American Technology
Corp.
Arrow Fastener Company,
Inc.
B & K
17
51
Precision-
Dynascan Corp.
32, 37
Bussmann Mfg.
Division
Cover 3
Castle Electronics, Inc.
57
Charous & Niebergall
57
Chemtronics Incorporated
67
Cleveland Institute
59
Dana Laboratories
67
Edison Electronics-Div.
McGraw Edison
29
John Fluke Mfg. Co.... Cover 4
GC Electronics
39
Gem City Tuner
11
Heath Company
59
Hickok Electrical
Instrument Co.
66
Jensen Tools and Alloys
57
Jerrold Electronics,
General Instrument
Corp.
23
Lectrotech, Inc
65
LogiMetrics, Inc
11
.
.
MTI
56
Mallory Distributor
Products
Mountain West Alarm
Supply Co.
Non -Linear Systems
Oelrich Publications
Oneida Electronic Mfg.
3
67
17
67
Co
33, 34, 35, 36
Perma Power Company
64
Phipps & Bird, Inc
14
Pomona Electronics
2
Precision Tuner
Service
Cover
Projector Recorder Belt
2, 1, 9
Co
RCA Distributor & Special
64
Products ...12,13,18,19,48,49
Sencore Inc.
42, 43
Sperry Tech, Inc
39
GTE Sylvania -ECG
Consumer Renewal
5
Tektronix, Inc.
25
Tuner Service Corp.
7
Ungar Div. of Eldon
Industries, Inc.
14
Wahl Clipper Corporation
66
ELECTRONIC SERVICING
Buss® Fuses
Specìalïze
Too!
in the protection o
four new BUSS fuse assortments
Now
exclusively designed with replacement fuses to
offering a
service most Citizen Band Radios
whole new area of opportunities for increased
profits.
5 in metal boxes
Two assortments contain 48
(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 con5 in metal boxes (80 fuses). BUSS
taining 16
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. 80CB-1
No. 240CB-3
Metal Display Stand
No. 240CB-4
Plastic Display Box
Ce]
Metal Display Stand
No. 80CB-2
Plastic Display Box
BUSSMANN MANUFACTURING
a McGraw -Edison Company Division
St. Louis, Missouri 53107
www.americanradiohistory.com
FLUKE PROVES AN INEXPENSIVE,
HANDHELD DMM
CAN BE BUILT WITHOUT LEAVING
EVERYTHING OUT.
Let's face it.
Before now, if you bought an inexpensive, handheld digital multimeter
you didn't get much- they just left
most everything out.
We knew that was no answer.
So we built the 8030A 31/2 -digit
DMM. It's a small, portable, inexpensive,
handheld DMM, but it performs like our
benchtop units.
With one basic difference. The
8030A was designed, built and tested to
a size and shape proven best for field
service and laboratory technicians. There's
a built-in hood that can be slipped forward
to shade the readout in sunshine. It has
rms capability. The best overload protection. Diode test. It weighs 2.2 pounds,
and will take a beating without failing.
Finally, we guarantee accuracy specifications for one year.
And it only costs $235*.
True rms.
1
-year accuracy specs.
Fluke
Fluke
High voltage protection.
Fluke
Diode test.
Fluke
A full line of accessories offering rf voltage,
high current ac, high voltage dc, and
temperature measurement probes.
Fluke
ment of rf voltages, high current ac,
high voltage dc and temperature.
80T-150 Temperature Probe
Sensitivity:
1 mV/°C or 1 mV/°F
Accuracy:
+15°C to +35°C ±2°C(3.6°F)-25°C to
ambient:
+125°C ±3°C(5.8°F)
-50°C to -25°C and
+125°C to +150°C
0°C to 15°C,35°C Add 1°C(1.8°F) to
to 50°C ambient: above
You can also get temperature measuring
capabilities with the 8030A.
And because the 8030A gives you
so much in performance, let us remind
"Fluke does the impossible again."
you once more of the price.
Only $235*.
For the first handheld DMM that's
small in size, small in price, but huge
in performance.
For data out today, dial our toll -free
There is extensive overload protection. It has been tested with transients up to 6000V peak across the
input terminals.
Options include two battery operations: a rechargeable NiCad for 8 hours
operation and thiow-away alkaline cells.
hotline, 800-426-0361.
John Fluke Mfg. Co., Inc., P.O. Box
43210, Mountlake Terrace, WA 98043
Fluke (Nederland) B.V., P.O. Box 5053,
Tilburg, The Netherlands.
Phone: (013) 673-973 Telex: 52237
Accessories include probes for measure-
*U.S. price only.
There's only one place to go for all the performance you need in a handheld DMM.
There are measurement functions
in five selectable ranges for dc volts,
ac volts (true rms), dc current, ac current (true rms), and resistance. DC voltage measurement is from 100 EtV to
1100V with basic accuracy of ±0.1%,
ac measurement is from 100 IN to 750V
rms with basic accuracy of ±0.5%. DC
and ac current is from 100 nanoamps to
1.999 amps with basic dc accuracy of
±0.35% and basic ac accuracy of ±1%.
Resistance measurement is from 100 milliohms to 2 megohms with a basic accuracy of ±0.4%.
We added true rms response for ac
measurements. Specified accuracy
is still attainable when the measured
waveform is distorted.
A NEW ADVANCE. 8030A DMM. FLUKE
For More Details Circle
(2) on Reply Card
www.americanradiohistory.com
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