Zenith 19M20 User manual

PHOTO PACT* Fold
er
ZENITH CHASSIS
19M20, U,Z, 19M21, U,UZ,Z
VOLUME
CONTROL
ON-OFF
SWITCH
ZENITHMODEL
CHANNEL
SELECTOR
SWITCH
M1800R
TRADENAMEZenith
i
MODELS
M1800E, M1800R, R1800EZ, R1800RZ, R1812EZ, R1812RZ
M1800EU, M1800RU, R1800EUZ, R1800RUZ,R1812EUZ,
R1812RUZ.
M1800EZ,M1800RZ
M2228R,M2229E,M2229R,M2230E,M2230R,M2230RZ2,
Ma249E, M2249R,M2250E, M2250R, M2252E, M2252R,
R2229EZ, R2229RZ,R2230EZ,R2230RZ,R2249EZ,
R2249RZ,R2250EZ,R2250RZ,R2257EZ,R2257RZ,
R2258EZ,R2258RZ .
M2228RU, M2229EU,M2229RU,M2230EU,M2230RU,
M2249EU, M2249RU,M2250EU,M2250RU,M2252EU,
M2252RU, R2229EUZ,R2229RUZ,R2230EUZ,R2230RUZ,
R2249EUZ, R2249RUZ,R2250EUZ,R2250RUZ,R2257EUZ,
R2257RUZ, R2258EUZ,R2258RUZ
M228RZ,M2229EZ, M2229RZV M2230EZ,M2230RZ,
M2249EZ,M2249RZ,M2250EZ,M2250RZ,M2252EZ,
M2252RZ ,
M2250RUZ
CHASSIS
19M20
19M2OU
19M20Z
19M21
19M21U
19M21Z
19M21UZ
MANUFACTURER Zenith Radio Corp. , 6001 Dickens Ave. , Chicago 39, Illinois
TYPE SET Television
TUBESNineteen
Receiver
POWERSUPPLY110-120 Volts AC-60 Cycle RATING 1.6 Amp. (a> 117 Volts AC
TUNING RANGE Channels 2
Drive Cord Stringing
thru 13 VHP, 14 thru 83 UHF,Video IF 45. 75 MC, Sound IF 41.25 MC
INDEX
6,7 Photographs (Cont)
(Intercarrier)
, . . , 23 Trans. , Inductor Si Alignment Identification
Horizontal Sweep Circuit Adjustments 11 Servicing inthe Field
Parts List and Descriptions ....
Photographs
Cabinet-Rear View
Chassis-Top View
RF Tuner
Resistor Identification
15 thru 18 Schematic (Alternate Tuner)
Schematic (TV)
11 Trouble Shooting Aids
4,9 Tube Failure Check Chart ........
3 Tube Placement Chart (Bottom View)
10, 21 Tube Placement Chart (TopView) ...
14,19
12,
20
8
22
13
2
21
5
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5
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HOWARD W. SAMS & CO.,INC. • Indianapolis 5, Indiana
"The listing ofany available replacement part herein does not constitute inany
case a recommendation,warranty or guaranty by Howard W. Sams & Co.,Inc.,
as tothe quality and suitability of such replacement part. The numbers of these
parts have beencompiledfrominformationfurnished to Howard W. Sams & Co.,
Inc., bythe manufacturers ofthe particulartype of replacementpart listed."
"Reproduction or use, without express permission, of editorial or pictorial con-
tent, in any manner, is prohibited. No patent liability is assumedwithrespect to
the useofthe informationcontained herein. Copyright1954 by Howard W.
Sams & Co.,Inc.,Indianapolis 5, Indiana, U.S.of America.Copyrightunder In-
ternational CopyrightUnion. All rights reserved under Inter-American Copyright
Union (1910) by Howard W. Sams & Co.,Inc."Printed inU.S.of America
DATE 12-54
SET 259 EOLDER 16

THE COOPERATION OFTHE MANUFACTURER OF THIS
RECEIVER MAKES IT POSSIBLE TO BRING YOU THISSERVICE
» MEASUBED FROM PIN 1
A PHOTOFACT STANDARD NOTATION SCHEMATIC
©Howard W. Sami & Co.,Inc. 1954
PAGE 2

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SET259 FOLDER 16
PAGE 3

CHASSIS BOTTOM VIEW-CA
PAGE 4

JJ28) (C32J (C27
W-CAPACITOR IDENTIFICATION
PAGE 9

TUBE PLACEMENTCHART
1ST VIDEO IF
TOP VIEW
INDICATES BLANK PINOR LOCATING KEYON TUBESOCKET
SYNC
TUBE FAILURECHECKCHART
The following; chart lists tubeswhosefailures are most likely to produce the indicatedsymptoms.
Refer to tubeplacementchart for location and type of tube.
POWER SUPPLY FAILURE
No raster, no sound - V18
LOSS OF PICTURE OR SOUND
No pic, no sound, has raster - V2,V3,V4,V5,V6
No pic, no sound, has snow - VI, V2,V3
No pic, has sound, has raster - V6,V7,V19
Has pic, no sound - V8,V9, V10
Overloadedpicture -V7
SYNC FAILURE
No vert, sync - VJ, Vll
Nohoriz. sync-Vll, V13, V14
No vert, or horiz. sync - Vll
SWEEP FAILURE
No raster, has sound - V14,V15,V16, VI7, V19, Fuse (Ml)
No vertical deflection - V7, V12
Poor vert, linearity or foldover - V7, VT2
Poor horiz. linearity or foldover - V14,V15, VI6
Narrow picture - V14,V16, V17, V18
Vert, off freq. - V7,Vll
Horiz. off freq.-Vll,V13, VM
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SET 259 FOLDER 16
PAGE 5

ALIGNMENT INSTRUCTIONS
1.
2.
3.
4.
The high voltage lead should be securely taped and keptaway from the chassis. Donot remove the horizontal oscillator tube (V14) to disable the
high voltage .
VIDEO IF ALIGNMENT
Connect the negative lead ofa 2 volt bias supply tothe ungroundedside of C31.
Connect the positive side to chassis.
Connect the synchronized sweepvoltage from the sweepgenerator tothe horizontal input ofthe oscilloscope for horizontaldeflection.
DUMMY
ANTENNA
470MMF
SWEEP
GENERATOR
COUPLING
High side topin 1 (grid)
of 6CB6 (V5). Low side
to chassis.
High side to point <^> .
Low side to chassis .
SWEEP
GENERATOR
FREQUENCY
43MC
(10MC Swp)
MARKER
GENERATOR
FREQUENCY
39.75MC
45.75MC
39.75MC
41.25MC
47.25MC
42.75MC
«.OMC
45.75MC
CHANNEL
Any non
interfer-
ing
channel
CONNECT
SCOPE
Vert. Amp.thru
10KSJ to point <$> .
Low side to chassis
ADJUST
A1.A2
A3.A4,
A5
A6, A7,
A8,A9
REMARKS
Attenuate generator output for3 volts
peak to peak on scope. Adjust for response
curve of maximumamplitude and sym-
metry similar to Fig. 1.
Remove bias battery. Use maximum
scopegain to amplify trapregion of
response curve asin Fig. 2. Adjust for
MINIMUM marker amplitude. Reconnect
bias supply.
Attenuate sweepgenerator output to
maintain not morethan 3 voltspeak to
peak on scope. Alternatelyadjust A6 thru
A9 to obtain response similar to Fig. 3.
A6 affects the high side andA7 affects
the low side ofthe response curve.
OSCILLATORALIGNMENT
The master oscillator adjustment,A10, istobe madeonly ifthe individualchannel oscillator adjustment fails to bring the channel within the
range ofthe fine tuning control. If channels 2 thru 6 fall within the range ofthe fine tuning control
but the higherchannels do not , slight adjustment ofA10maybe necessary to bring inthe higher channels ,
Connect the negativelead ofthe bias supply tothe ungroundedside of C31.Connect the positive lead to chassis. Adjust for -1 volt at C31.
Turn upthe scopegain so that the soundtrap notch inthe responsecurvebecomes visible,.
Connect the synchronizedsweep voltage from the sweep generator tothe horizontal input ofthe oscilloscope for horizontal deflection.
The sweepgenerator output leadshould be terminated with its characteristic impedance,usually 50 ohms.
Setthe fine tuningcontrol tothe mid-position ofits range.
DUMMY
ANTENNA
Two 120S2
Carbon
Resistors
SWEEP
GENERATOR
COUPLING
Acrossantennater-
minalswith 120S2 in
each lead.
SWEEP
GENERATOR
FREQUENCY
57MC
(10MC Swp
63 MC
(10MC Swp
69MC
(10MC Swp
79MC
(10MC Swp
85MC
(10MC Swp
177MC
(10MC Swp
183MC
(10MC Swp
189MC
(10MC Swp
195MC
(10MC Swp
201MC
(10MC Swp
207MC
(10MC Swg
213MC
(10MC Swp
MARKER
GENERATOR
FREQUENCY
59.75MC
65.75MC
71.75MC
81.75MC
87.75MC
179.75MC
185. 7 SMC
191.75MC
197.75MC
203.75MC
209.75MC
215.75MC
CHANNEL
2
3
4
5
6
7
8
9
10
11
12
13
CONNECT
SCOPE
Vert. Amp.thru
lOK.fl to point <£> .
Low side to chassis
ADJUST
All
A12
A13
A14
A15
A16
A17
A18
A19
A20
A21
A22
REMARKS
Adjust to placesound marker in trap
notch asin Fig. 4.
FIG.
FIG.2
FIG.3 FIG.4
PAGE 6

ALIGNMENT INSTRUCTIONS (cont)
HF AND MIXER ALIGNMENT
Remove the bias supply from C31and connect a jumper from the tuner AGC lead (yellow) to chassis.
Connect the synchronizedsweepvoltage from the sweep generator tothe horizontalinput ofthe oscilloscope for horizontal deflection.
The sweepgenerator output leadshould be terminatedwith its characteristic impedance, usually 50 ohms.
DUMMY
ANTENNA
Two 120S2
Carbon
Resistors
SWEEP
GENERATOR
COUPLING
Across antennater-
minalswith 120S2 in
each lead.
SWEEP
GENERATOR
FREQUENCY
69MC
(10MC Swp)
201MC
(10MC Swp)
MARKER
GENERATOR
FREQUENCY
67.25MC
71.75MC
199.25MC
203.75MC
CHANNEL
4
11
CONNECT
SCOPE
Vert. Amp.thru
10KS3 to point ^> .
Low side to chassis.
ADJUST
A23,
A24,
A25
A26,
A27,
A28
REMARKS
Adjust for response similar to Fig. 5.
Adjust A26andA27for symmetrical
response similar to Fig. 6. Adjust A28
for properbandwidth.Repeat steps 5
and 6 until best overall symmetrical
response is obtained.Removejumper
from tuner AGC terminal to chassis.
SOUND IF ALIGNMENT
Connect an attenuator {Zenith part #3-17203 or equivalent) in series with the receiverantenna.
Tune ina tonemodulated TV signal and adjust the attenuatoruntil the signal falls below the limiting level ofthe 6BN6 limiter detector, as
evidenced bya hiss similar to superregeneration.
Adjust the sound take-offtransformer(A29,A30) the sound IF transformer(A31) andthe quadrature coil (A32) for maximumsound of best
quality.
Adjust the buzzcontrol (R9) for minimum intercarrier buzz.
IIthe intercarrier buzzcannot be eliminatedwith the buzz control check the setting oftheAGC delaycontroladjustment.
II during the sound IF alignment the signal rises above the limitinglevel (hiss disappears) increase the attenuationuntil the hiss returns.
UHF TUNER ALIGNMENT
7.
8.
9.
Alignment oftheUHF tunershould notbe attempted unless proper test equipment is available.
Switch the receiver totheUHF position .
Connect the negative lead ofa 2 volt bias supply tothe ungrounded side of C31.Connect the positive lead to chassis.
Adjust the sweepgeneratoroutput to provide 3 volts peak to peak on scope,
Connect the synchronizedsweepvoltage from the sweep generator tothe horizontal input ofthe oscilloscope for horizontal deflection.
The sweepgenerator output leadshould be terminated with its characteristic impedance, usually 50 ohms.
DUMMY
ANTENNA
Fig. 8
SWEEP
GENERATOR
COUPLING
Across UHF antenna
terminalsthru
matching network(Fig.
8).
SWEEP
GENERATOR
FREQUENCY
713MC
(10MC Swp)
473MC
887MC
(10MC Swp)
MARKER
GENERATOR
FREQUENCY
711.25MC
471.25MC
885.25MC
CHANNEL
54
14
83
CONNECT
SCOPE
Vert.Amp.thru
IOKSI to point <$> .
Low side to chassis.
ADJUST
A33.A34,
A35
A36, A37
A38
REMARKS
Tunerrocket arm should beinthe horizontal
position. If necessary, loosen set screw and
adjust tuner shaft so that rocker armis
horizontal when the channelindicator isset
to channel 54.Donot adjust A33 unless
oscillator calibration isoff more than
three channels. If necessary, adjust A33to
place videomarket at50%on response
curve asin Fig. 7, The image(weaker re-
sponse) will appear also. The response to-
ward the counter clockwiseposition ofA33
isthe correct response. Adjust A34and
A35 for maximumamplitude and symmetry
of response similar to Fig* 7.
Check for response similar to Fig. 7.If
oscillator isoff morethan 3 channels
adjust the oscillator travel (osc., mixer and
ant, travel adjustments arethe three round
thumb screws ontopof tuner)adjustment to
scale. Care must be used in making this
adjustment soasnotto move the rocker
armoutofits bearing. Setthe mixer and
antenna travel adjustments for maximum
response on scope.
Adjust A36to place video marker at50%as
in Fig. 7. Adjust A37 andA38for maximum
amplitude and symmetry of response similar
to Fig. 7.
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FIG.5
F IG.6
FIG. 7
\ON CONTINUOUS TUNER
FIG. 8
PAGE 7