Zenith MC7031 User manual

SERVICEMANUAL
MODELMC7051
ILLUSTRATED
STEREORECEIVERS
MODELS MC7031,MC7041, MC7051
ZENITH RADIOCORPORATION
PARTS ANDSERVICEDIVISION
11000SEYMOURAVENUE.FRANKLINPARK.ILLINOIS 60131
HF-46
22.8M-CPC
JUNE, 1980
PRINTED IN U.S.A.
$4.00
923-972

To the Service Technician
PRODUCT SAFETY SERVICINGGUIDELINES FORALL AUDIOAMPLIFIERS AND RADIORECEIVERS
CAUTION: No modification ofany circuitshould be attempted.
Serviceworkshould be performedonly after you are thoroughly
familiar with all of the followingsafetychecks and servicingguide-
lines. To do otherwiseincreases the risk of potential hazards and
injury tothe user.
SAFETYCHECKS
SUBJECT:Fire & ShockHazard
1. Be surethat all components are positioned in such a way
toavoidpossibility of adjacentcomponentsshorts.This
isespeciallyimportant on thosechassiswhich are trans-
ported toand from the repairshop.
2Alwaysreplace all protectivedevicessuch as insulators
andbarriersafterworking ona receiver.
3.Check for frayedinsulation on wiresincluding theAC
cord. Alsocheckacross-the-linecomponents for damage
andreplace if necessary.
4 All fuses and certainresistors and capacitorswhich are
of the flameprooftype(shaded onthe schematic di-
agrams and partslists)must be replacedwithexact
Zenithtypes to preventpotentialfirehazard.
5Afterre-assembly oftheset alwaysperform anAC leak-
agetest onthe exposedmetallicparts ofthe cabinet
such asthe knobs,antennaterminals, etc.tobe sure the
set is safe to operatewithoutdanger of electricalshock.
Do notusea lineisolationtransformerduringthistest. Use
an AC voltmeterhaving5000ohms per volt or more sen-
sitivity inthe followingmanner:Connect a 1500ohm10
wattresistor,(63-10401-76)paralleled bya .15mfd,AC
typecapacitor(22-4384)between a knowngoodearth
ground(waterpipe,conduit, etc.)andthe exposedmetal-
licparts, oneata time.Measure theAC voltageacross
thecombination 1500ohm resistor and.15mfd. capac-
itor.Reverse theAC plug onthesetand repeat AC volt-
agemeasurements for eachexposedmetallicpart.Volt-
agemeasuredmust not exceed 0.75 volts RMS. Thiscor-
responds to0.5 milliamp AC.Any valueexceedingthis
limitconstitutes a potentialshockhazard and must be
correctedimmediately.
goodearthground
such asthe water
pipe, conduit, etc.
placethisprobe
oneachexposed
metallicpart.
TABLE OF CONTENTS
SafetyServicingGuidelinesandTechnicalApplicationsIndexInsideFrontCover
Index to SchematicsandRelatedDrawingsPage 1
ProductFeaturesPages 2-5
RecordChangerFeaturesPage 6
TapeUnitFeaturesPage 7
IntroductionPage 8
ProductFeaturesPage 9
GeneralInformationPage 10
AlignmentProceduresPages 11-15
DisassemblyPages 16-19
Theory and ApplicationPages20-22
PartsListsPages24-36
IntegratedCircuitBlockDiagramsPages 38-41
Schematic,RelatedDrawingsandExplodedViewsPages43-60
TECHNICALAPPLICATIONSINDEX
Various "HF" seriesservicemanualscontaininformationrelating to solidstatedevicetheory,operation and circuitapplications as
introducedinto our products. In addition,serviceprocedures are alsoexplained, if required, inthe appropriateservicemanuals.
Suchinformationhasbeenincluded inthe followingservicemanuals:
HF 18: Theory - Diodes(IncludingZenerandSCR),Transistors,(PNP,NPN,Darlington,andJFET).Applications - Chassis29AT24(JFETFM-RF,
Multiplex,ElectronicTouchSwitching),ComplementarySymmetry,Chassis11ZT27(ElectronicFilter).
HF 22: Theory - JFET,IGFET,MOSFET,Applications - DualGate MOSFETFM-RF,JFETBiplexDetector,Quasi-ComplementarySymmetry.
HF 23: Applications - ModelC9029/Chassis15WCA10FourChannelDecoder.
HF 26: Applications - Chassis15WDR51(JFETMeterCircuit,Multiplex IC, FourChannelDecoding).
HF 27: Applications - ModelSD2568SpeakerSwitchingCircuitry.
HF 28: Applications - ModelD9013WAllegroSpeakerSystem.
HF 29: Theory— LightEmittingDiodes(LED).Applications - ThreeLightTuning(TargetTuning),Multiplex IC.
HF29S1:Applications—Snap-offEscutcheon andOut FrontChassisRemoval, "E" LineModels.
HF 30: Applications — Snap-offEscutcheon andOut FrontChassisRemoval, "F" LineModels.
HF31:Theory and Applications - Chassis12WGR59(CeramicFilters, IFIC, QuadratureDetector,InterstationMuting, PLL Multiplex IC, Audio).
GeneralProductInformation — AudioCircuitry(including TwoonTwo SpeakerMatrix,AllegroSpeakerSystems), "G" LineDisassembly
Procedures.
HF32S2:Applications - FourChannelSoundReproductionInput Vs. Output,RepairingPushButtonSwitches,RecordChanger and PhonoCartridge
InterChangeability,Chassis12WGR59Accessibility.
HF 32: Applications - "H" LineDisassemblyProcedures, PartNumberIdentification,RecordChanger and PhonoCartridgeInter Changeability, "H"
LineAllegroSpeakerSystemsandRepairProcedures.
HF33: Theory and Applications - Chassis3WJR52(CeramicFilters, IFIC'sforAMandFM QuadratureDetector, PLL Multiplex IC, Audio).
GeneralProductInformation—AudioCircuitry(includingOutput IC), "J"LineDisassemblyProcedures.
HF33S1:Applications—"J"LineAllegroSpeakerSystemRepairProcedures.
HF 34: Applications— "K" LineAllegroSpeakerSystems and RepairProcedures.GeneralProductInformation.
HF 39: Applications - "K" LineAllegroSpeakerSystems and RepairProcedures.
ACVOLTMETER

INDEX
*REFERTOMASTERINDEXFORUPDATEDINFORMATION
CHASSIS INFORMATION PRIORDATA CHASSIS INFORMATION PRIORDATA
ORMODEL ONPAGE CONTAINEDIN ORMODEL ONPAGE CONTAINEDIN
1WEA10(Z1) -HF
28S1, 29,30 J3000W1 — HF33
1WEA11(Z1) -HF
28S1, 29,30 E9012W(1) -HF
29S1, 30
1WGR50 -HF31S1.31S2 G9012W1 -HF
31, 31S1
1WJR55 -HF33,33S1 E9014W(1) -HF
29S1, 30
3WEA10(ZD -HF29,29S2,30 E9014X(1) -HF
29S1, 30
3WGR50 -HF31.31S1 G9014W -HF31S1
3WHR50 -HF32,32S1 E9018WO) -HF
29S1, 30
3WJR50,50Z -HF33,
33S1, 34 G9019W -HF31.31S1
3WJR51,51Z -HF33,33S1 E9026W -HF30S1
3WGR52 -HF
31, 31S1 E9029W -HF29S1
3WHR52 -HF32S1 IS4020 -HF35
3WJR52,52Z -HF33.33S1 IS4021 -HF41
3WGR54 -HF
31, 32S1 IS4030 -HF35
3WR10X -
HF40, 47 IS4031 -HF41
3WR11X -HF40.47 IS4040 -HF35
3WR12X -
HF40, 47 IS4041 -HF41
5WER50 -HF28S1,29,29S1,30,30S1 IS4060 — HF36
5WFR50 -HF30,
31S1, 31 IS4061-1 -HF42
5WER51 -HF29,29S1,30,30S1 IS4061-2 -HF43
5WFR51 -HF30.30S1 IS4070 -HF36
5WER52 -HF29S2,30,30S1 IS4071-1 -HF42
5WER52Z1 -HF30,30S1 IS4071-2 -HF43
5WER52Z2 -HF30,30S1 IS4080 -HF36
5WER52Z3 -HF30,30S1 IS4081-1 -HF42
5WER53 -HF29,
29S1, 30 IS4081-2 _ HF43
5WFR53 -HF30,30S1 IS4081-3 _ HF44
6WGR55 -HF
31, 31S1 MC1000 _ HF39
6WHR55 -HF32,32S1 MC1000-11 -HF39
6WGR56 -HF31,31S1 MC1000-12 - -
6WHR56 -HF32,32S1 MC2000 -HF39
6WGR57 -HF
31, 31S1 MC2000-11 -HF39
6WHR57 -HF32.32S1 MC2000-12 - -
6WGR90 -HF31S1 MC3000 -HF39
6WGR91 -HF31S2 MC3000-11 -HF39
8WJR56 -HF33 MC3000-12 - -
8WJR57 -HF33 MC4000 -HF39
12WGR58 -HF
31, 32S1 MC4000-11 -HF39
12WGR59 -HF
31, 31S1 MC4000-12 --
12WHR29 -HF32,32S1 MC6010 -HF37
15WJR29 -HF33,
33S1, 34 MC6020 -HF45
15WEA10 -HF
29S1, 30 MC6060 -HF37
15WFR51 -HF30,30S1 MC6060-1 -HF37S1
15WER55 -HF29,29S1,29S2,30,30S1 MC6065 -HF45
15WFR55 -HF30,30S1 MC7030 -HF38
15WER56 -HF29,29S1,29S2,30 MC7031 8to60 -
15WFR57 -HF30,30S1 MC7040 -HF38
35WFR50 -HF30,
30S1, 32S1 MC7041 8to60 -
G1000W -HF31./31S1 MC7050 -HF38
H1000W,W1,W2,W3 HF32 MC7051 8 to60 -
J1000W1,W2 -HF33 MC9020 -RC28
G2000W -HF
31, 31S1 MC9025 -RC33
G2000W11 -HF31S1 MC9030 -RC29
H2000W,W3 -HF32 MC9035 -RC34
J2000W1,W2 -HF33 MC9040 -RC30
G3000W -HF31,31S1 MC9050 -RC37
G3000W11 -HF31S1 MC9070 -TR41
H3000W,W3 -HF32 MC9070-1 -TR41S1
HF28S1isPartNo.923-734 HF29isPartNo.923-740 HF29S1isPartNo.923-762 HF29S2isPartNo.923-784
HF30isPartNo.923-809 HF30S1isPartNo.923-841 HF31isPartNo.923-848 HF31S1isPartNo.923-857
HF31S2isPartNo.923-864 HF32isPartNo.923-874 HF32S1isPartNo.923-895 HF33isPartNo.923-901
HF33S1isPartNo.923-921 HF34isPartNo.923-927 HF35isPartNo. 923-933 HF36isPartNo.923-934
HF37isPartNo.923-942 HF38isPartNo.923-943 HF39isPartNo 923-944 HF40isPartNo.923-945
HF41isPartNo.923-962 HF42isPartNo.923-966 HF43isPartNo.923-967 HF44isPartNo.923-970
HF45isPartNo. 923-971 HF46isPartNo.923-972 HF47isPartNo 927973 HF48isPartNo.923-974
1

PRODUCT FEATURES
SEENOTES ON PAGE 5
• REFER TO PAGE ONE INDEX FOR MODELS IN THISMANUAL •
CABINET CHASSIS SPEAKERS RECORD
CHANGER OTHERFEATURES
MODEL COLOR STYLE
NOTE A
MODEL TYPE PART
NUMBER
IMPED.
(In
Ohms)
QTY.
AND SIZE
(In Inches)
PART
NUMBER
NOTE B
TAPE
PROVISION
NOTE C
SPEAKER
PROVISION
NOTE D
MISC.
NOTE E
IS4021 Walnut
M,D - AM/FM/FM
Stereo/Phono/
Tape
Note D2 -- 169-573 8TK-R/P
969-51
A1, A2,
SPKAB
AUX,DL,H,
HIF, LD,T,
TO
IS4031 Walnut
M,D — AM/FM/FM
Stereo/Phono/
Tape
Note D2 — —
169-573 CASS-R/P
969-52
A1, A2,
SPKAB
AUX,DL,H,
HIF, LD,T,
TO
IS4041 Walnut M,D
AM/FM/FM
Stereo/Phono/
Tape
Note D2 169-573 CASS-R/P
969-52
8TK-R/P
969-51
A1, A2,
SPKAB
AUX,DL,H,
HIF, LD,T,
TO
IS4061-1 Walnut
M,D AM/FM/FM
Stereo/Phono/
Tape
Note D2
169-579 8TK-R/P
969-55
A1, A2,
A3, A4,
SPKOAB
AUX,DL,F,
H,HIF,LD,
LOF, MS,
MU, T,TO
IS4061-2 Walnut
M,D AM/FM/FM
Stereo/Phono/
Tape
Note D2
169-579 8TK-R/P
969-51
A1, A2,
A3, A4,
SPKOAB
AUX,DL,F,
H,HIF,LD,
LOF, MS,
MU,T,TO
IS4071-1 Walnut
M,D AM/FM/FM
Stereo/Phono/
Tape
Note D2
169-579 CASS-R/P
969-56
A1, A2,
A3, A4,
SPKOAB
AUX,DL,F,
H,HIF,LD,
LOF, MS,
MU,T,TO
IS4071-2 Walnut
M,D AM/FM/FM
Stereo/Phono/
Tape
Note D2 169-579 CASS-R/P
969-56
A1, A2,
A3, A4,
SPKOAB
AUX,DL,F,
H,HIF,LD,
LOF, MS,
MU, T,TO
IS4081-1 Walnut M,D
AM/FM/FM
Stereo/Phono/
Tape
Note D2 169-579 CASS-R/P
969-56
8TK-R/P
969-55
A1, A2,
A3, A4,
SPKOAB
AUX,DL,F,
H,HIF,LD,
LOF, MS,
MU,T,TO
IS4081-2 Walnut
M,D
AM/FM/FM
Stereo/Phono/
Tape
Note D2
169-579 CASS-R/P
969-56
8TK-R/P
969-51
A1, A2,
A3, A4,
SPKOAB
AUX,DL,F,
H,HIF,LD,
LOF, MS,
MU,T,TO
IS4081-3 Walnut
M,D AM/FM/FM
Stereo/Phono/
Tape
Note D2
169-579 CASS-R/P
A-8051
8TK-R/P
A-7021
A1, A2,
A3, A4,
SPKOAB
AUX,DL,F,
H,HIF,LD,
LOF, MS,
MU,T,TO
IS4090 Walnut
M,D
AM/FM/FM
Stereo/Phono/
Tape
Note D2
169-579 CASS-R/P
969-62
A1, A2,
A3, A4,
SPKOAB
AUX,DL,F,
H,HIF,LD,
LOF, MS,
MU,T,TO
L900P Pecan C,LL
3WR10X AM/FM/FM
Stereo/Phono/
Tape
49-1153-02
49-1094-01
16
45
2-6x9
2-31/2
169-573-01 8TK-P
969-60
A1, A2,
SPK
AFC, AUX,
DL, H,HIF,
T,TO
LR902P Pecan C,LL
3WR11X AM/FM/FM
Stereo/Phono/
Tape
49-1153-02
49-1094-01
16
45
2-6x9
2-3%
169-573-01 8TK-R/P
969-51
A1, A2,
SPK
AFC, AUX,
DL, H,HIF,
RS, T,TO
LR902P1 Pecan C,LL
3WR11X AM/FM/FM
Stereo/Phono/
Tape
49-1153-02
49-1094-01
16
45
2-6x9
2-31/2
169-573-01 8TK-R/P
969-51
A1, A2,
SPK
AFC, AUX,
DL, H,HIF,
RS,T,TO
LR912AE Antique
Oak C,LL
3WR11X AM/FM/FM
Stereo/Phono/
Tape
49-1261-02
49-1251-02
8
8 2-8 2-3
169-581 8TK-R/P
969-51
A1, A2,
SPK A,AFC,
AUX,DL,H,
HIF, RS,T,
TO
LR915P Pecan
C,LL 3WR11X AM/FM/FM
Stereo/Phono/
Tape
49-1261-02
49-1251-02
8
8 2-8
2-3
169-581 8TK-R/P
969-51
A1, A2,
SPK A,AFC,
AUX,DL,H,
HIF, RS,T,
TO
2

PRODUCT FEATURES
SEENOTES ON PAGE 5
• REFER TO PAGE ONE INDEX FOR MODELS IN THISMANUAL •
CABINET CHASSIS SPEAKERS RECORD
CHANGER OTHERFEATURES
MODEL COLOR STYLE
NOTE A
MODEL TYPE PART
NUMBER
IMPED.
(In
Ohms)
QTY.
AND SIZE
(In Inches)
PART
NUMBER
NOTE B
TAPE
PROVISION
NOTE C
SPEAKER
PROVISION
NOTE D
MISC.
NOTE E
LR915P1 Pecan
C, LL
3WR11X AM/FM/FM
Stereo/Phono/
Tape
49-1261-02
49-1251-02
8
8 2-8 2-3
169-570 8TK-R/P
969-51
A1, A2,
SPK A,
AFC
AUX, DL,H,
HIF, RS,T,
TO
LR915P2 Pecan
C, LL
3WR11X AM/FM/FM
Stereo/Phono/
Tape
49-1261-02
49-1251-02
8
8 2-8 2-3
169-570 8TK-R/P
969-51
A1, A2,
SPK A,
AFC,
AUX, DL,H,
HIF, RS,T,
TO
LR916PN Pine
C, LL
3WR11X AM/FM/FM
Stereo/Phono/
Tape
49-1261-02
49-1251-02
8
8 2-8
2-3
169-581 8TK-R/P
969-51
A1, A2,
SPK A,
AFC,
AUX, DL,H,
HIF, RS, T,
TO
LR916PN1 Pine
C, LL
3WR11X AM/FM/FM
Stereo/Phono/
Tape
49-1261-02
49-1251-02
8
8 2-8
2-3
169-570 8TK-R/P
969-51
A1, A2,
SPK A,
AFC,
AUX, DL,H,
HIF, RS,T,
TO
LR917M Pecan
C, LL
3WR11X AM/FM/FM
Stereo/Phono/
Tape
49-1261-02
49-1251-02
8
8 2-8
2-3
169-581 8TK-R/P
969-51
A1, A2,
SPK A,
AFC,
AUX, DL,H,
HIF, RS,T,
TO
LR919P Pecan
C, LL
3WR12X AM/FM/FM
Stereo/Phono/
Tape
49-1261-02
49-1251-02
8
8 2-8
2-3
169-586 8TK-R/P
969-51
A1, A2,
SPK A,
AFC,
AUX, DL,H,
HIF, RS,T,
TO
LR919P1 Pecan
C, LL
3WR12X AM/FM/FM
Stereo/Phono/
Tape
49-1261-02
49-1251-02
8
8 2-8 2-3
169-571 8TK-R/P
969-51
A1, A2,
SPK A,
AFC,
AUX, DL,H,
HIF, RS,T,
TO
LR920AE Antique
Oak C,
LL
3WR12X AM/FM/FM
Stereo/Phono/
Tape
49-1217-01
49-1166-01
8
8 2-10
2-3%
169-586 8TK-R/P
969-51
A1, A2,
SPK A,
AFC,
AUX, DL,H,
HIF, RS,T,
TO
MC1000 Walnut
M,SP — —
49-1277
49-1278
8
8
1-61/2
1-2
— — 20
Watt
Handling
Capability
A1
MC1000-11 Walnut
M,SP — — 49-1277
49-1278-02
8
8 1
-61/2
1-2
— 20
Watt
Handling
Capability
A1
MC1000-12 Walnut
M,SP — — 49-1277
49-1278
8
8
1-61/2
1-2
— — 20
Watt
Handling
Capability
A1
MC2000 Walnut
M, SP
49-1293
or
49-1261-02
49-1166-01
8
8
8
1-8
1-8
1-31/*
40 Watt
Handling
Capability
A2
MC2000-11 Walnut
M, SP
49-1293
or
49-1261-02
49-1166-01
8
8
8
1-8
1-8
1-31/2
40 Watt
Handling
Capability
A2
MC2000-12 Walnut
M, SP
49-1293
or
49-1261-02
49-1166-01
8
8
8
1-8
1-8
1 -3%
40 Watt
Handling
Capability
A2
MC3000 Walnut
M, SP
— —
49-1290
49-1288-01
8
8
1-10
1-31/2
— — 60
Watt
Handling
Capability
A3
MC3000-11 Walnut
M, SP
— —
49-1290
49-1288-01
8
8
1-10
1 -31/2
— 60
Watt
Handling
Capability
A3
MC3000-12 Walnut
M, SP
—
49-1290
49-1288-01
8
8
1-10
1 -31/2
— 60
Watt
Handling
Capability
A3
3

PRODUCT FEATURES
SEENOTES ON PAGE 5
• REFER TO PAGE ONE INDEX FOR MODELS IN THISMANUAL •
CABINET CHASSIS SPEAKERS RECORD
CHANGER OTHERFEATURES
MODEL COLOR STYLE
NOTE A
MODEL TYPE PART
NUMBER
IMPED.
(In
Ohms)
QTY.
AND SIZE
(In Inches)
PART
NUMBER
NOTE B
TAPE
PROVISION
NOTE C
SPEAKER
PROVISION
NOTE D
MISC.
NOTE E
MC4000 Walnut
M,SP --
49-1291
49-1289
49-1288-01
5.5
7.0
8.0
1-12
1-5
1 -31/2
--100
Watt
Handling
Capability
A4
MC4000-11 Walnut
M,SP — —
49-1291
49-1289
49-1288-01
5.5
7.0
8.0
1-12
1-5
1-31/2
— — 100
Watt
Handling
Capability
A4
MC4000-12 Walnut M,SP — —
49-1291
49-1289
49-1288-01
5.5
7.0
8.0
1-12
1-5
1 -31/2
— — 100
Watt
Handling
Capability
A4
MC6020 Walnut
M
AM/FM/FM
Stereo/Tape Note
D2 Note B3 8TK-R/P
969-54
A1, A2,
SPKOAB
AFC, AUX,
DL, F,H,
HIF, LD,
LOF, MS,
MU,T,TO
MC6065 Walnut M
AM/FM/FM
Stereo/Tape Note
D2 Note B3 CASS-R/P
969-59
A1, A2,
A3, A4,
SPKOAB
AFC, AUX,
DL, F,H,
HIF, LD,
LOF, MS,
MU, T,TO
MC7031 Walnut M
AM/FM/FM
Stereo Note
D2 Note B3 TM
A2, A3,
A4
SPKOAB
AFC, AUX,
DE, DL,F,
H,HIF,LD,
LOF, MS,
MU,TIO,TM,
TS, TZ
MC7041 Walnut M
AM/FM/FM
Stereo Note
D2 Note B3 TM
A3, A4,
SPKOAB
AFC, AUX,
DE, DL,F,H,
HIF, LD,LOF,
MS,MU,TIO,
TM,TS,TZ
MC7051 Walnut
M AM/FM/FM
Stereo Note
D2 Note B3 TM
A3, A4,
SPKOAB
AUX,DE,DL,
F,H,HIF,
LD, LOF,MS,
MU, 2TIO,
TD, TM,TS,
TZ
MC9020 Walnut
M,D --- - -
169-574
- - -
MC9025 Walnut
M,D - - - - -
169-579
-- -
MC9030 Walnut
M,D --- - -
169-575
---
MC9035 Walnut
M,D -- - --
169-580
-- -
MC9040 Walnut
M,D -----
169-576
---
MC9050 Walnut M,D -- - - - - - -
MC9070 Walnut
M -1ape -- - -
CASS-R/P
969-58
-H
MC9070-1 Walnut M -
Tape
----
CASS-R/P
969-63
-H
SL2597P9 Pecan
C,2LL 3WR12X AM/FM/FM
Stereo/Phono/
Tape/Color
Combo
49-1276
49-1234-04
49-1166
8
16
8
2-10
1-5
2-H
169-585 8TK-R/P
969-51
A2, A3,
A4,
SPK
A,AFC,AUX,
DL, H,HIF,
T,TO
4

PRODUCT FEATURES
NOTES
NOTEA - CABINETSTYLE:
C= Console,D = DustCover,M = Modular,LL- LiftLid,2LL- Two
LiftLids,SP= SpeakerSystem.
NOTED2:"K"and"L"ModelsmayuseeitherMC1000,MC2000,
MC3000orMC40008 ohmAllegroSpeakerSystemsasindicated.(See
SpeakerProvisions).
NOTEB - RECORDCHANGERS
NOTEB1:Provisionforexternalrecordchangerusinga ceramiccartridge.
NOTEB2:Provisionforexternalrecordchangerusinga magnetic
cartridge.
NOTEB3:Provisionforexternalrecordchangerusingeithera ceramic
ormagneticcartridge.
RecordChangershavingalphasuffixes(i.e.169-511A)denotevariations
ofinternalmechanicaland/orelectricalcomponents(refertoRecord
ChangerFeaturescharts)butotherwiseareinterchangeablewithother
alphasuffixandnon-suffixversions.
NOTEC - TAPEINPUTANDOUTPUTPROVISIONS:
FactoryInstalled:8 TK- EightTrackCartridge.
Cass= Cassette,P = Play,R = Record.
TM= TopofSetModelforinstallationwiththedesignatedconsoleor
modularmodels:
ModelMC9070- CassetteTapePlayer/Recorder.
TapeUnitshavingalphasuffixes(ie.169-510A)denotevariationsof
internalmechanicaland/orelectricalcomponents(refertoTapeUnit
Featureschart)butareotherwiseinterchangeablewithotheralpha
suffixandnon-suffixversions.Unitshavingnumeric(ie.169-506O1)
ornumeric/alpha(ie.169-506-01A)suffixesmayhavea oneway
interchangeabilityundersomeconditions(refertoProductFeatures
chart).
NOTED - SPEAKERPROVISIONS:
NOTED1:ModelsE9012series,G1000W,G2000W,W11,G3000W,
W11, G9012W1, G9014W,G9019W,H1000Wseries,H2000Wseries,
H3000Wseries,J1000Wseries,J2000WseriesandJ3000Wseriesare
8ohmAllegroSpeakerSystems.AllegroModelsintheE9014and
E9018serieswere16ohmsystems.
A1= ModelMC1000Allegro1000SpeakerSystemmaybeused.
A2= ModelMC2000Allegro2000SpeakerSystemmaybeused.
A3= ModelMC3000Allegro3000SpeakerSystemmaybeused.
A4= ModelMC4000Allegro4000SpeakerSystemmaybeused.
SPK= SwitchtoselectInternal(Main),External(Remote)orBoth
SpeakerSystems.
SPKAB= SwitchtoselectA,B orBothSpeakerSystems.
SPKOAB= SwitchtoselectA,B orBothSpeakerSystemsortoswitch
allSpeakerSystemsoff.
NOTEE - MISCELLANEOUSFEATURES:
A =SpeakerSystemisAllegro.
A1 = SpeakerSystemisAllegro1000.
A2 =SpeakerSystemisAllegro2000.
A3 = SpeakerSystemisAllegro3000.
A4 = SpeakerSystemisAllegro4000.
AFC =AFCDefeatSwitch.
AUX = AuxiliaryinputacceptscertainoptionalRecordChangersor
TapeUnitslistedunderNotesB andC.
DE = DeemphasisSwitch.
DL =DialScaleLight.
F = FlywheelTuning.
H = HeadphoneJack(Stereo).
HIF = HiFilterSwitch.
LD =LoudnessSwitch.
LOF = LoFilterSwitch.
MS = Mono/StereoSwitch.
MU =FMMuteSwitch.
PL =PowerIndicatorLight(otherthanDialScaleLight).
RS =RecordStorage.
T = TuningMeter.
TD = TapeDubbingSwitch.
TIO =TapeInput/Output.
TM = TapeMonitorSwitch.
TO =TapeOutput.
TS =SignalStrengthMeter(AMandFM).
TZ = ZeroCenterTuningMeter(FM).
5

RECORDCHANGERFEATURES
SEENOTESBELOW
PART
NUMBER
MFG.
CODE
CART-
RIDGE,
STYLUS
NOTE 2
PRESSURE
INGRAMS
45
RPM
ADAPTER
NOTE 4
MODES
(TYPE) SIZE (TYPE) SPEED (TYPE) RECORD STACK
TURN-
TABLE
DIA.
BASE
PLATE
COLOR
TURN-
TABLE
PAD
COLOR
PRES-
SURE
ARM
COLOR
MISC.
(TYPE)
169-570 GAR
6200C 142-199
56-643
0.7D-3.0S
3.0-5.0
A-7545
or
76-2132
Off,Manual,
Auto
(Slide)
12", 33
7", 33
7", 45
10", 78
(Slide)
Note 5 10
1/2"
Metal Black Black Chrome
and
Black
Cue
(Lever)
169-571 GAR
630S 142-192
56-643
0.7D-3.0S
3.0-5.0
A-7545
or
76-2132
Off,Manual,
Auto
(Slide)
12", 33
7", 33
7", 45
10", 78
(Slide)
Note 5 10
1/2"
Metal Black Black Chrome
and
Black
Viscous Cue
(Lever)
Anti-Skate
(Slide)
169-573 BSR
C197 142-197 56-639
0.7D-3.0S
3.5-5.0
S-72648,
A-6616
or
A-8352
Off,Manual,
Auto
(Slide)
7,10,12
(Slide) 33,45,78 (Slide) Note
5
11"
Metal Black Black Black Cue
(Lever)
169-573-01 BSR
C197 142-198 56-642
0.7D-3.0S
3.5-5.0
S-72648,
A-6616,
or
27-628
Off,On,
Auto
(Slide)
7,10,12
(Slide) 33,45,78 (Slide) Note
5
11"
Metal Black Black Black Cue
(Lever)
169-574 GAR
630S 142-194
56-641
0.6D
3.5-5.0
A-7545
or
76-2132
Off,Manual,
Auto
(Slide)
12", 33
7", 33
7", 45
10", 78
(Slide)
Note 5 10
1/2"
Metal Black Black Chrome
and
Black
Viscous Cue
(Lever)
Anti-Skate
(Slide)
169-574-01 GAR
630S 142-189
56-641
0.6D
3.5-5.0
A-7545
or
76-2132
Off,Manual,
Auto
(Slide)
12", 33
7", 33
7", 45
10", 78
(Slide)
Note 5 10
1/2"
Metal Black Black Chrome
and
Black
Viscous Cue
(Lever)
Anti-Skate
(Slide)
169-575 GAR
GT4 142-195 56-641-02
0.4X0.7D
2.5-4.5
27-627
or
76-2132
Off,Manual,
Auto, Repeat
(Slide)
N.A.
33, 45
(Slide) Note
5 11
1/4"
Metal N.A. Black N.A. Viscous
Cue
(Slide)
169-575 GAR
GT4 142-195 56-641-02
0.4X0.7D
2.5-4.5
27-627
or
76-2132
Off,Manual,
Auto, Repeat
(Slide)
N.A.
33, 45
(Slide) Note
5
(Belt
Drive)
N.A. Black N.A.
Anti-Skate
(Rotary)
Start/Reject
(Button)
169-575-01 GAR
GT4 142-189
56-641
0.6D
2.5-4.5
27-627
or
76-2132
Off,Manual,
Auto-Repeat
(Slide)
N.A. 33, 45
(Slide) Note
5 11
1/4"
Metal N.A. Black N.A. Viscous
Cue
(Slide)
169-575-01 GAR
GT4 142-189
56-641
0.6D
2.5-4.5
27-627
or
76-2132
Off,Manual,
Auto-Repeat
(Slide)
N.A. 33, 45
(Slide) Note
5
(Belt
Drive)
N.A. Black N.A.
Anti-Skate
(Rotary)
Start/Reject
(Button)
169-576 GAR
GT25 142-196
56-641-03
0.4X0.7D
1.5-3.0
27-627
or
76-2132
Off,Manual,
Automatic,
Repeat
(Rotary)
7, 12
(Rotary)
33, 45
(Rotary) Note
5
11 1/4"
Metal Gray Black N.A. Viscous
Cue
(Slide)
169-576 GAR
GT25 142-196
56-641-03
0.4X0.7D
1.5-3.0
27-627
or
76-2132
Off,Manual,
Automatic,
Repeat
(Rotary)
7, 12
(Rotary)
33, 45
(Rotary) Note
5
(Belt
Drive)
Gray Black N.A.
Anti-Skate
(Rotary)
Start/Reject
(Rotary)
169-579 TENVA
MT30 142-200 56-641-04
0.6D
2.0-4.0
76-2132 Program
Off,Manual,
1Through 6
(Slide)
Play
(Button)
N.A. 33, 45
(Slide) Note
5
11"
Aluminum
Metal
Black Black N.A. Damped
Cue
(Lever)
Anti-Skate
(Rotary)
BeltDrive
24PoleMotor
169-580 TENVA
MT60 142-195 56-641-02
0.4X0.7D
2.0-4.0
Program
Off,Manual,
1Through 6
(Slide)
Play
(Button)
N.A. 33, 45
(Slide)
Pitch
Control
(Rotary)
Note 5
11"
Aluminum
Metal
Black Black N.A. Damped
Cue
(Lever)
Anti-Skate
(Rotary)
BeltDrive
ElectronicDrive
AndSpeed
Control
24_PpleMotor
StrobeIndicator
169-581 BSR
C198 142-190
56-643
0.7D-3.0S
3.0-5.0
A-6616
or
27-628
Off,On.
Auto
7,10,12
(Slide) 33,45,78
(Slide) Note
5 10
1/2"
Plastic Black Black Black Cue
(Lever)
Anti-Skate
(Rotary)
2PoleMotor
169-585 TENVA
MT30 142-201
56-647
0.7DX3.0S
3.0-5.0
Program
Off,Manual,
1Through 6
(Slide)
Play
(Button)
N.A. 33, 45
(Slide) Note
5
11"
Aluminum
Metal
Black Black N.A. Damped
Cue
(Lever)
Anti-Skate
(Rotary)
BeltDrive
24PoleMotor
169-586 BSR
C218 142-202 56-647
0.7D-3.0S
3.0-5.5
27-628 Off,On,
Auto
7,10,12
(Slide) 33,45
(Slide) Note
5 10
1/2"
Plastic Black Black Black Cue
(Lever)
Anti-Skate
(Rotary)
BeltDrive
4PoleMotor
NOTE 1 — All recordchangershave120VAC60Hzmotors.
NOTE 2 — D = Diamond, S = ManufacturedSapphire.
NOTE 3 — Stylus 56-641, hasa 0.6mil spherical tip. 56-641-01 isan optional 2.5milmfg sapphirestylus for playing 78RPM records.56-641-02
and56-641-03 are Bi-radialElipticalstylus.
NOTE 4 — Adapter27-628 isa disctype and 76-2132 isa stubtype.Adapterusedwillvarywithmodel.
NOTE 5 — Recordchangerswillplay as many as five(flat and unwarpedrecords in 12-inch,10-inch or 7-inch size.Sizescannot be intermixed.)
NOTE 6— Recordchangerswillplay as many assix (flat and unwarpedrecords in 12-inch,10-inch or 7-inch size.Sizescannot be intermixed.)
6

TAPE UNITFEATURES
SEENOTESBELOW
PARTNO.
NOTEF
MFG.
CODE
8-TRACK/
CASSETTE
CHANNELS ALC/FULL
FEATURE
NOTEA
MOTOR
NOTEB
AUTO
STOP
NOTEC USE
NOTED
MISC. FEATURES
NOTEE
PARTNO.
NOTEF
MFG.
CODE
8-TRACK/
CASSETTE PLAY RECORD
ALC/FULL
FEATURE
NOTEA
MOTOR
NOTEB
AUTO
STOP
NOTEC USE
NOTED
MISC. FEATURES
NOTEE
169-50601A AMI/ML
8-Track
2 2 Full DC/M Full C
A2,C1, FF,I,M,
P1, R
169-545 AMI/ML 8-Track
2 2 ALC DC/M Four
R c
A2, C3,I,R
169-546 AMI/ML
8-Track
2 2 ALC DC/M Four
R/FFA
c A2, C3,FF,I,P2,R
96951 TAN
8-Track
2 2 ALC
Full DC/M FourR, FourR/FF C,M
A3, C3,FF,I,P2,
R,RL
96952 TAN Cassette 2 2 ALC DC/E Tape
P/R M
A3, C4,CR,E,F,I,
P2, RL,TC
969-54 TAN
8-Track
2 2 Full DC/M FourB
P/R/FF
M A3, C3,FF,I,M,
P2, R,R L
969-55 TAN 8 Track 2 2 Full DC/M Four
R/FF M
A3, C3,FF,I,M,
P2, RL,RP
969-56 TAN Cassette 2 2 Full DC/E Tape
P/R M
A3, C4,CR,E,F,I,
M,P2,R L,TB,TC,
TE
969-57 TAN Cassette 2 2 Full DC/E Tape
P/R M
A3, C3,E,F,I,M,
P2, RL,T,TB,TC,
TE
96958 AM
I
Cassette 2 2 Full DC/E Tape
All MA
A1, C1,D,E,I,
M,P2,PRL,RL,
TB3, TC,TE3
969-59 VOR Cassette 2 2 Full DC/E Tape
P/R M
A3, C3,CR,D,E,
F,I,M,P2,RL,
T,TB/TE,TC
96960 TAN 8-Track
2 - - DC/M -C
A2, C3
969-61 VOR Cassette 2 2 Full DC/E Tape
P/R M
A3, C3,E,F,I,M,
P2, RL,T,TB,TC,
TE
969-62 AMI Cassette 2 2 Full DC/E Tape
P/R M
A3, C3,CR,D,E,
F,I,M,P2,RL,
TB/TE, TC
969-63 AMI Cassette 2 2 Full DC/E Tape
All MA A1
, C1,D,E,I,M,
P2, PRL,RL,TB3,
TC, TE3
A-7021 TAN 8-Track
2 2 Full DC/M Four
R/FF M
A2, C3,FF,I,M,
P2, RL,PP
A-8051 TAN Cassette 2 2 Full DC/E Tape
P/R M
A2, C4,CR,E,F,I,
M,P2,RL,TB,TC,
TE
NOTES
NOTEA - RECORD
ALC= AutomaticLevelControl
Full= FullFeaturewithRecordLevelControlsandMeters.
NOTEB - MOTOR
E= ElectronicGovernor
M= MechanicalGovernor
ACMotorsrequireconversionkitifusedon50Hz.
NOTEC - AUTOSTOP
Full= Stopsaftereachprogram,fourthprogramorrunscontinously(in
bothPlayandRecordmodes).Selectedbythreepositionslidecontrol.
FourR = StopsafterfourthprograminRecordonly.
FourR/FF= StopsafterfourthprograminRecordandFastForwardonly.
Four R/FFA = StopsafterfourthprograminRecordandafterall
programsinFastForward.
FourB P/R/FF = StopsafterfourthprograminPlay,RecordandFast
ForwardonlyifAutoStopButtonisdepressed.
TapeP/R= TapetensionsensoratendoftapeinPlayandRecordonly.
TapeAll= StopsatendoftapeinPlay/Record/FastForward/Rewind
modes.
NOTED - USEDIN
C= Console
M= Modular
MA= ModularAccessory
W= WedgeModular
NOTEE - MISC.FEATURES
A1
=
ParallelBladePowerConnector.
A2
= MolexTypePowerConnector.
A3 = HardWirePowerConnector.
B
=
BiasFrequencySwitch.
C1
=
RCATypeAudioConnector.
C2 = SpadeLubAudioConnector.
C3
=
HardWireAudioConnector.
C4 = MolexTypeAudioConnector.
CR
=
Cue/Review.
D =
DolbyNoiseReductionSystem.Dolbyisa trademarkofDolby
Laboratories,I nc.
E
= Eject.
F
=
InterlockedFastForwardButton.
F F
FastForwardButton(Push-PushType).
I
=
InterlockedRecordButton.
M = RecordLevelMeter(Illuminated).
P1
=
PauseButton(PushIn,SlideLefttoLock).
P2
= PauseButton(Push-Push).
PRL
= PeakRecordLight.
Q Automatic2/4ChannelSwitching,withmodeindicator.
R = ReadyLightorAutoStopLight.
RL
=
RecordLight.
RP = RepeatButton.
T
=
TapeRunLight.
TB = TapeBiasSwitch(CrO2/Normal).
TB3
=
TapeBiasSwitch(CrO2/FeCr/Fe3O2) •
TC
=
TapeCounter.
TE = TapeEqualizationSwitch(Cr02/Normal).
TE3
=
TapeEqualizationSwitch(High,Mid,Low).
NOTEF - PARTNUMBERS
169- Basenumbersidentifyunitswithelectronicswhile969-andA-
basenumbersidentifyunitswithoutelectronics(mechanismonly).
FeatureslistedinNotes"A","C"and"E"for969-andA-basenumbers
includefeatureswhichmayvarywithmodelapplication.
7

INTRODUCTION
Thisservicemanualcontainsdetailedserviceinformationforcommonamongthethree,
allsectionsofModels MC7031, MC7041and MC7051.
OnthefollowingpagesareFeatureChartsandSpecifications
Illustrationsofthethreemodelscoveredinthisservicemanualofthethreemodels,
appearbelow.Aswillbenotedfromtheillustrations,stylingis
8

PRODUCTFEATURES
XORLETTERDENOTESFEATUREINCLUDEDANDNUMBERDENOTESQUANTITY:D = ROTARYDETENTACTION(CENTER
DETENTONBALANCECONTROL),F = ROTARYFLYWHEEL,K = KEYBOARDTYPE,P = PUSHBUTTONTYPE,
R= ROTARYTYPE,S = SLIDETYPE,T = TOGGLETYPE
FEATURES MODELNUMBER MC7031 MC7041 MC7051 FEATURES MODELNUMBER MC7031 MC7041 MC7051 FEATURES FEATURES
PRODUCTTYPE AM/FM AM/FM AM/FM PRODUCTTYPE AM/FM AM/FM AM/FM
POWEROUTPUT TUNER/AMPLIFIERCONNECTORS
(Min. R.M.S. perChannel) 15W 25W 40W TAPEINPUT X X 2
T.H.D.NOMORETHAN
0.1%
0.08% 0.05% TAPEOUTPUT X X 2
BANDWIDTHOF 20Hz- 20Hz- 20Hz- PHONOIN- CERAMIC X X -
INTOAN8 OHMLOAD 20kHz 20kHz 20kHz PHONOIN- MAGNETIC X X 2
TUNER/AMPLIFIERCONTROLS AUXILIARYINPUT X X X
VOLUME D D D SPEAKEROUTPUT-
BALANCE D D D PUSHTYPE(Pair) 2 2 2
TREBLE D D D HEADPHONE(STEREO) X X X
BASS D D D EXTERNALANTENNA
TUNING F F F FM-300OHMBALANCED X X X
TUNER/AMPLIFIERSWITCHES FM- 75OHMUNBALANCED X X X
POWER T T T AM X X X
LOUDNESS P T T ACOUTLETS- UNSWITCHED X X X
HIFILTER P T T SWITCHED - - X
LOFILTER P T T PHONOGROUNDTERMINAL X X X
SPEAKER MICROPHONEINPUT - - X
OFF, A,B orA+B R R R
MONO/STEREO P T T
FMMUTE P T T TUNER/AMPLIFIERFEATURES
FMAFC P T -FMSTEREOINDICATORLIGHT X X X
FMDE-EMPHASIS(onback) S S S FUNCTIONINDICATORLIGHTS X X X
TAPEMONITOR P T T TUNINGMETER(ILLUMINATED)
TAPEDUBBING - - T CENTERREADINGFM X X X
BANDSWITCH- POSITIONS 4 4 6 SIGNALSTRENGTHMETER
AM R R R FM/AM(ILLUMINATED) X X X
FM R R R SPEAKERPROTECTIONFUSES X X -
PHONO R R 2R SPEAKERPROTECTIONCIRCUIT --X
AUXILIARYINPUT R R R
MICROPHONE --R
9

GENERALINFORMATION
THEORY
FromtimetotimeZenithincludestheuseofnewcomponents
andcircuitapplicationsinproductdesign.Theoryandexpla-
nationofsuchcomponentsandcircuitsisincludedinvarious
manuals.Refertoinsidefrontcoverforfurtherinformation.
CIRCUITBOARDCOMPONENTIDENTIFICATION
InordertoassisttheServiceTechnician,mostcircuitboards
aremarkedtoidentifythelocationofcomponents,testpoints,
etc., usingtheschematicreferencesymbolsandnumbers.
Wehavealsoprepareda drawingofthefoilsideofthecircuit
boardshowingtherelationshipbetweenthecomponentsand
the foil. ThiswillaidtheTechnicianinquicklytracingcircuits,
asnotonlyarethecomponentsshown,butalsothevoltagesat
variouscheckpoints.Componentsareidentifiedbya letter/
numbercombination.A letterprefixtoindicatethetypeof
component:C=Capacitor,L=Coil,R=Resistor,CR=Diode,etc.
Thenumbersareassigned,inblocks,toidentifythecircuitin
whichitisused:
BlockStageExample
1- 99FMTunerR1,C1,L1.
101- 199AMTunerR101,C101,L101.
201- 299IFR201,C201,L201.
301- 399MultiplexR301,C301,L301.
401- 449MainPreamp,RightChannelR401,C401,L401.
451- 499MainPreamp,LeftChannelR451,C451,L451.
501- 599PowerSupplyR501,C501,L501.
901- 949PhonoPreamp,RightChannelR901,C901,L901.
951- 999PhonoPreamp,LeftChannelR951,C951,L951.
1401- 1449PowerAmp,RightChannelR1401,C1401, L1401.
1451- 1499PowerAmp,LeftChannelR1451,C1451, L1451.
c.RemovetheoldICandbecertainthattheholesinthe
circuitboardarefreeofsolder.
d. Applya heatconductivegreasetothemetalheatsink
surfaceagainstwhichthemetalplateoftheICwillbe
placed. Thisgreasecanbeobtainedinquantitiesby
orderingPartNo.205-303.
e.InsertICpinsintocorrectholesinthecircuitboard.
f.Inserta screwthrougheachoftheIC'smountingholes.
Tightenthescrewsuntiltheyaresnug.CAUTION—
Donotovertightenthesescrewsastoomuchforcemay
causeinternaldamagetotheIC.
g. Solderallleads,beingcertainthatsolderdoesnotbridge
tootherpins,causingshortswhichmaydamagetheIC
orexternalcomponents.
4.Donotoperatetheseamplifierswithouttheirproper
speakerload.
5.Donotshortouttheaudiooutputofeitherchannelwhen
theamplifierisoperating.
FMAGCVOLTAGECURVE
VoltagedevelopedattheAGCterminaloftheIFIC(pin15)
variesdependingontheIFvoltagesampledinthechip.Ifa
fixedinputsignallevelwereappliedtoseveralsamplesofa
givenchassismodel,themeasuredAGCvoltageforthat
inputlevelwillvaryamongthesamples.Voltagemeasured
undertheseconditionsisnota completeindicatorofproper
AGCaction.
Twoimportantpointsmustbenoted:
1. Generalshapeofthevoltagecurve(whenthevoltagesare
Whenservicingtheseproducts,theServiceTechnicianmustplottedfora curve).
considerthefollowing:
2. AGCvoltagewillstarttodropastheRFinputlevelin-
1. Oneintegratedcircuitisusedforbothchannelsofthepowercreasestoapproximately1000microvolts.
outputstages.• • • • • • •
2. Shoulda poweroutputstage fail;
a.Checkforshortsbetweentheintegratedcircuitoutputs
(pins5 and11)andotherpins.
b.CheckvoltagesattheICpins.
c.CheckfordefectivecomponentsexternaltotheIC,
includinginthepowersupply.
3.ReplacethepoweroutputICinthefollowingmanner.
a.A replacementpoweroutputICnormallyhasa kinkin
eachpin.Thisisthepointatwhichthepinsaretobe
bentwhenrequiredtofitthecircuitboard.
b.Bendthepinsatrightanglesatthekinkineachpin.
CAUTION— Donotflexleadsasthismaycauseinternal
damagetotheIC.
MINIMUMRATEDPOWEROUTPUTPERCHANNELINTO8 OHMS
(SINEWAVECONTINUOUSAVERAGEPOWER-
OFTENCALLEDRMSPOWER)
MODELS NUMBEROF
CHANNELS WATTSPER CHANNEL POWER
BANDWIDTH
TOTALHARMONIC
DISTORTION(THD)
NOMORETHAN
MC7031 2 15 20Hz-20KHz
0.1%
MC7041 2 25 20Hz-20KHz 0.08%
MC7051 2 40 20Hz-20KHz 0.05%
10

AM/FM/MULTIPLEXALIGNMENT
GENERAL
Thesereceivershavebeenalignedatthefactoryandnormally
willnotrequirefurtheradjustment.Asa result,itisnot
recommendedthatanyattemptbemadetoalterthestages.
Ifanycomponentsarereplacedorifanyonetamperswith
theadjustments,realignmentmaybenecessary.
AMALIGNMENT
ItisrecommendedthatAMIF'sbealignedbythesweep
methodshowninthealignmentprocedureonthefollowing
pages. Ifyoursignalgeneratordoesnothavesweepcapabilities
fortheAMIF,usethealternatealignmentprocedureshown.
FMALIGNMENT
Becauseofthewidebandpassrequiredina FMMultiplex
tuner,itisdesirabletouseanFMsignalgeneratorhavinga
deviationof250kHzaswellasanoscilloscope,whenaligning
boththeFMIFandRFportionsofthisreceiver.Itisnotonly
necessarytoobtainmaximumamplitudeintheIFamplifier
stages, butalsonecessarytomaintainsymmetry.Itisdesirable
tousemarkersinobtainingIFcurvesymmetry.
Capacitorsmentionedinthealignmentprocedureshouldbeas
smallinsizeaspossibleandthegroundleadofthegenerator
mustbeconnectedtogroundascloseaspossibletothepoint
ofinjection.
MULTIPLEXALIGNMENT
Beforeanyattemptismadetoalign,orservice,FMMultiplex
circuitry,thetechnicianmustbecertainthattheRF,IF,and
Detectoralignmentiscorrect,andthatthereceiverfunctions
normallyonmonauralsignals.
MostMultiplexgeneratorsareexcellenttroubleshootingde-
vicesbecausetheyprovidea compositeMultiplexsignalaswell
asanRFsignal(whichisFMmodulatedbythecomposite
multiplexsignal).Thecompositesignalisveryusefulsinceit
canbeusedinsignaltracingtheMultiplexportionofthe
SCOPE PATTERN "A "
receiver.WedonotrecommendthatMultiplexalignmentbe
madeusingthecompositesignalinjectedattheoutputter-
minaloftheDetectorsincethereisalwaysomephaseshift
occurringintheRF,IForDetectorcircuits.Asa result,
Multiplexalignmentmadebya signalinjectedattheDetector
inputwouldnotbecorrect.ForproperMultiplexalignment,
thecompositesignalmustFMmodulatetheRFcarrierand
thenbefedintotheFMantennaterminals.Withthesignal
injectedinthismanner,theMultiplexalignmentwouldthen
bethebestthatcouldpossiblybeobtained.
RFsignalsshouldbeinjectedata pointintheFMbandwhere
nosignalispresent.Ifatallpossible,thisshouldbeata
frequencynearthemiddleoftheFMband.TunetheFM
receivertothispointandadjusttheRFfrequencyadjustment
onthegeneratortothissamefrequency.TheAGCvoltage
developedinthereceivershouldbemaximum.TheAGC
voltagesubstantiallylessthanthismayindicatetheRF
frequencyistunedtoanimage.
GENERALTROUBLE-SHOOTINGPROCEDURE
Shoulda problemariseinaligningtheFMMultiplexportion
ofthereceiver,thetechnicianmustdeterminewhetherthe
difficultyliesintheRF,IF,andDetectorportionsofthe
receiver,orwhetherthedifficultyliesintheMultiplexportion.
Thecompositeoutputofthemultiplexgeneratorcanbe
injectedattheoutputoftheDetectortohelpdeterminethe
areaofdifficulty.Toreducepossibleextraneoussignals
comingthrougha Detector,shorttheDetectorprimarywitha
jumperlead.Thewaveformsandtheirmagnitudemayvary
slightlyfromchassistochassis,however,theyarequite
indicativeofwhatwillbeseenwhensignaltracingthe
Multiplexcircuitry.
Ifallthewaveformsaresimilarinformandmagnitudeto
thoseindicated,itcanbeassumedthattheMultiplexportion
ofthereceiverisfunctioningproperlyandtheproblemlies
aheadofthisintheFMreceiver.Ifanyofthewaveformsare
missingata latterpointbutareapparentata previouspoint,
circuitrybetweenthetwotestpointsshouldbechecked.
SCOPE PATTERN "B"
PROBE "A" - RF INPUT PROBE "B"- DE-EMPHASIS PROBE "C"- DETECTOR PROBE
11

RF, IF,MPXANDAUDIOALIGNMENTPROCEDURE
FORMODELS MC7031, MC7041
STEP CONNECT GENERATOR
TO DUMMY
ANTENNA
CONNECT
VTVM/
SCOPETO
INPUT
SIGNAL
FREQ.
SETDIAL
TO ADJUST PURPOSE
AUDIOOUTPUTIDLECURRENTADJUSTMENT
CAUTION: BeCertainThatTheOutputStagesHaveBeenAdjustedForProperIdleCurrentUnderNoSignalInputConditionsBeforePerform-
ingOtherAdjustmentsOrAlignment.
1 VTVM
AcrossR 1422
NoSignal
Input R1412 AdjustControlsFor4mVAcross
CorrespondingResistors.This
WouldBeApproximately15mA.
2 AcrossR1472
NoSignal
Input
R1462
AMALIGNMENT- PREFERREDMETHOD- WITHAMSWEEPGENERATOR
NOTE: ForAMIFAlignmentUseAMSweepSignalGeneratorOf10KHzDeviation,60HzModulationForFullBandpassDisplay.Bandswitch
InAM.AlsoConnectModulationFrequencyToScopeHorizontal.(IfAMSweepNotAvailable,SeeSteps17Through31.)
3 ShortTestPoint"L"(AMGangAntennaSection)ToChassisGround.
4 TestPoint"K"
AMIFInput
Generator
Output
Probe"A"
Scope
Detector
Output
AcrossR123,
Term.#104
+455KHz Gang
Closed -AdjustGeneratorToCenter
FrequencyOfCeramic Filter.
5
TestPoint"K"
AMIFInput
Generator
Output
Probe"A"
Scope
Detector
Output
AcrossR123,
Term.#104
TuneGeneratorToCenterTotalBandpass
Waveform.DoNotChangeGeneratorFrequency
ForRemainderOfAMIFAlignment.
AdjustGeneratorToCenter
FrequencyOfCeramic Filter.
6
TestPoint"K"
AMIFInput
Generator
Output
Probe"A"
Scope
Detector
Output
AcrossR123,
Term.#104
Center Freq.
OfCeramic
FilterInT102
Gang
Closed
L104, L105
(T102) AdjustForMaximumGainAnd
Symmetry.
7
TestPoint"K"
AMIFInput
Generator
Output
Probe"A"
Scope
Detector
Output
AcrossR123,
Term.#104
Center Freq.
OfCeramic
FilterInT102
Gang
Closed
T103 AdjustForMaximum.
8
TestPoint"K"
AMIFInput
Generator
Output
Probe"A"
Scope
Detector
Output
AcrossR123,
Term.#104
Center Freq.
OfCeramic
FilterInT102
Gang
Closed
T104
AdjustForMaximum.
9
TestPoint"K"
AMIFInput
Generator
Output
Probe"A"
Scope
Detector
Output
AcrossR123,
Term.#104
RepeatSteps6,7 & 8 ForMinimumChange.
AdjustForMaximum.
1 0 RemoveShortBetweenTestPoint"|_"AndChassisGround.
1 1 OneTurnLoosely
CoupledToAM
Wavemagnet
Antenna
None Scope 1400KHz 1400KHz C1K SetOscillatorToDialScale.
12
OneTurnLoosely
CoupledToAM
Wavemagnet
Antenna
None
Detector
Output
AcrossR 1 23,
Term. #104
600KHz 600KHz T101
SetOscillatorToDialScale.
13
OneTurnLoosely
CoupledToAM
Wavemagnet
Antenna
None
Detector
Output
AcrossR 1 23,
Term. #104
RepeatSteps11& 12ForMinimumChange.
SetOscillatorToDialScale.
14
OneTurnLoosely
CoupledToAM
Wavemagnet
Antenna
None
Detector
Output
AcrossR 1 23,
Term. #104 1400KHz 1400KHz
C1 G AlignAntennaStage.
15
OneTurnLoosely
CoupledToAM
Wavemagnet
Antenna
None
Detector
Output
AcrossR 1 23,
Term. #104 600KHz 600KHz L111IfNecessary
AlignAntennaStage.
16
OneTurnLoosely
CoupledToAM
Wavemagnet
Antenna
None
Detector
Output
AcrossR 1 23,
Term. #104
RepeatSteps14& 15ForMinimumChange.
AlignAntennaStage.
AMALIGNMENT- ALTERNATEMETHOD- IFAMSWEEPGENERATORISNOTAVAILABLE
NOTE: ForAMIFAlignmentUseA SignalWith400HertzModulation.BandswitchinAM.
17 ShortTestPoint"L"(AMGangAntennaSection)ToChassisGround.
18 TestPoint"K"
AMIFInput
Generator
Output
Probe"A"
VTVM
Detector
Output
AcrossR123,
Term. #104
+455KHz Gang
Closed -
19
TestPoint"K"
AMIFInput
Generator
Output
Probe"A"
VTVM
Detector
Output
AcrossR123,
Term. #104
RockGeneratorWhileAdjustingL104
(T102Primary)ForMaximum. AdjustForMaximum.
20
TestPoint"K"
AMIFInput
Generator
Output
Probe"A"
VTVM
Detector
Output
AcrossR123,
Term. #104 RockGeneratorWhileAdjustingL105
(T102Secondary)ForMaximum.
AdjustForMaximum.
21
TestPoint"K"
AMIFInput
Generator
Output
Probe"A"
VTVM
Detector
Output
AcrossR123,
Term. #104
RepeatSteps19& 20ForMinimumChange.
AdjustForMaximum.
22
TestPoint"K"
AMIFInput
Generator
Output
Probe"A"
VTVM
Detector
Output
AcrossR123,
Term. #104
EqualOutputShouldBeFoundIfGenerator
IsDetunedEqualFrequencyEachSide
Maximum.
AdjustForMaximum.
23
TestPoint"K"
AMIFInput
Generator
Output
Probe"A"
VTVM
Detector
Output
AcrossR123,
Term. #104
Center Freq. Of
CeramicFilter
InT102
Gang
Closed 11 03
AdjustForMaximum.
24
TestPoint"K"
AMIFInput
Generator
Output
Probe"A"
VTVM
Detector
Output
AcrossR123,
Term. #104
Center Freq. Of
CeramicFilter
InT102
Gang
Closed T104
AdjustForMaximum.
25 RemoveShortBetweenTestPoint"L"AndChassisGround.
26 OneTurnLoosely
CoupledToAM
Wavemagnet
Antenna
None VTVM 1400KHz 1400KHz
C1 K SetOscillatorToDialScale.
27 OneTurnLoosely
CoupledToAM
Wavemagnet
Antenna
None Detector
Output
AcrossR123,
Term. #104
600KHz 600KHz T101
SetOscillatorToDialScale.
28
OneTurnLoosely
CoupledToAM
Wavemagnet
Antenna
None Detector
Output
AcrossR123,
Term. #104
RepeatSteps26& 27ForMinimumChange.
SetOscillatorToDialScale.
29
OneTurnLoosely
CoupledToAM
Wavemagnet
Antenna
None Detector
Output
AcrossR123,
Term. #104 1400KHz 1400KHz C1G AlignAntennaStage.
30
OneTurnLoosely
CoupledToAM
Wavemagnet
Antenna
None Detector
Output
AcrossR123,
Term. #104 600KHz 600KHz L111IfNecessary
AlignAntennaStage.
31
OneTurnLoosely
CoupledToAM
Wavemagnet
Antenna
None Detector
Output
AcrossR123,
Term. #104
RepeatSteps29& 30ForMinimumChange.
AlignAntennaStage.
FMALIGNMENT
NOTE: ForFMIFAlignmentUseA SignalOf250KHzDeviation,50HertzModulationForFullBandpassDisplay.BandswitchInFM.MuteOFF.AFC
OFF. PresetR208,R211,R303AndR313ToMidRotationBeforeConnectingGenerator.ConnectGeneratorCableGroundToGangFrame.
32 ShuntC1DToGroundWithA .001MFCapacitor.
33 TestPoint"D"
FMIFInput
AtQ2Base
Generator
Output
Probe"A"
Scope
Detector
Probe"C"
TestPoint
"G"
AtIC201
Pin1
±10.7MHz Gang
Closed -AlignI.F.TransformerForMaxi-
mumOutputAndSymmetryAs
IndicatedInScopePattern"A".
34
TestPoint"D"
FMIFInput
AtQ2Base
Generator
Output
Probe"A"
Scope
Detector
Probe"C"
TestPoint
"G"
AtIC201
Pin1
TuneGeneratorToCenterTotalBandpass
Waveform.DoNotChangeGeneratorFrequency
ForRemainderOfFMIFAlignment.
AlignI.F.TransformerForMaxi-
mumOutputAndSymmetryAs
IndicatedInScopePattern"A".
35
TestPoint"D"
FMIFInput
AtQ2Base
Generator
Output
Probe"A"
Scope
Detector
Probe"C"
TestPoint
"G"
AtIC201
Pin1 Center
Freq.
OfCeramic
FiltersY201,
Y202, Y203.
Gang
Closed T201
AlignI.F.TransformerForMaxi-
mumOutputAndSymmetryAs
IndicatedInScopePattern"A".
12

RF, IF,MPXANDAUDIOALIGNMENTPROCEDURE
FORMODELS MC7031, MC7041- Cont'd.
STEP CONNECT
GENERATOR
TO
DUMMY
ANTENNA
CONNECT
VTVM/
SCOPETO
INPUT
SIGNAL
FREQ. SETDIAL
TO ADJUST PURPOSE
36 TestPoint"A"
FMAntennaPost
(DisconnectAntenna)
300Ohm +98MHz 98MHz R211
(Mute) AdjustForNoSoundOutput
WhenInputIsBelow 1.7/xV
WithMuteSwitchON.
37
TestPoint"A"
FMAntennaPost
(DisconnectAntenna)
300Ohm +98MHz 98MHz
R208
(Meter) AdjustForA ReadingOf6 On
MeterM102With60dbV(1mV)
Input.
NOTE: ForFMDetectorAlignmentUseA SignalOf75KHzDeviation,1 KHzModulation.AlsoConnectGeneratorModulationFrequencyTo
ScopeHorizontal.AdjustGeneratorIFFrequencyToCenterTotalBandpassWaveform.DoNotChangeGeneratorIFFrequencyFor
RemainderOfIFAlignment.(IfYourGeneratorDoesNotProvideOutputForAudioModulationFrequencyUseHorizontalOutput
FromGenerator,OrScopeHorizontalSweep,AndFollowStep38C.)MinimumDistortionCanOnlyBeAchievedByUseOfStep38A
Below.
38 TestPoint"D"
FMIFInput
AtQ2Base
Generator
Output
Probe"A"
A.Distortion
Analyzer
(Thrua 100
UseeDe-
emphasis
Network
Probe"B"
AndScope.
B.Scope
C.Scope
Center
Frequency
OfCeramic
FiltersY201,
Y202, Y203.
Gang
Closed
L205, L206
(T202) A.PreferredMethod:Distortion
AnalyzerAtTestPoint"H"
ShouldReadMinimumDistortion.
B.AlternateMethod:AdjustFor
LinearScopeTrace- NoCurveAt
EndsOfTrace.DisregardMeter
Reading.
C.AlternateMethod:AdjustFor
MaximumLengthAndSymmetry,
SimilarToScopePattern"B".
39
TestPoint"D"
FMIFInput
AtQ2Base
Generator
Output
Probe"A"
TestPoint
"H"
Center
Frequency
OfCeramic
FiltersY201,
Y202, Y203.
Gang
Closed
L205
(T202) AdjustForCenterReadingOn
TuningMeterM101.
40 TestPoint"A"
FMAntennaPost
(DisconnectAntenna)
300Ohm 106MHz 106MHz C1E SetOscillatorToDialScale.
41
TestPoint"A"
FMAntennaPost
(DisconnectAntenna)
300Ohm
90MHz 90MHz L4
SetOscillatorToDialScale.
42
TestPoint"A"
FMAntennaPost
(DisconnectAntenna)
300Ohm
RepeatSteps40& 41ForMinimumChange.
SetOscillatorToDialScale.
43
TestPoint"A"
FMAntennaPost
(DisconnectAntenna)
300Ohm
106MHz 106MHz C1C AlignFMDetectorStageFor
Maximum.
44
TestPoint"A"
FMAntennaPost
(DisconnectAntenna)
300Ohm
90MHz 90MHz L2IfNecessary
AlignFMDetectorStageFor
Maximum.
45
TestPoint"A"
FMAntennaPost
(DisconnectAntenna)
300Ohm
106MHz 106MHz
C1 A AlignFMAntennaStageFor
Maximum.
46
TestPoint"A"
FMAntennaPost
(DisconnectAntenna)
300Ohm
90MHz 90MHz L1
AlignFMAntennaStageFor
Maximum.
47
TestPoint"A"
FMAntennaPost
(DisconnectAntenna)
300Ohm
RepeatSteps43Thru46ForMinimumChange.
AlignFMAntennaStageFor
Maximum.
NOTE: ApplySufficientSignalLevel— Approx.100Microvolts— ToObtainFullLimitingAtPointNear98MHz.
48 Frequency
CounterAnd/
orScope
TestPoint
"M"
Unmodulated
RF Carrier R303 (VCO) A.FrequencyCounterShouldRead
19KHz,+100Hz.
B.AlternateMethod:ConnectTest
Point"M"SignalToScopeVertical
AndAnAccurate19KHzSignalTo
ScopeHorizontalInput.AdjustFor
OneSquareSynchronizedWaveform.
49
ScopeAnd/Or
ACVTVM
LeftTape
Output
98MHz
10% Pilot
(L+ R)(L- R)
(LOnly)
R313 AdjustForSeparation.Maximum
LeftOutput.
50 RightTape
Output.
98MHz
10% Pilot
(L+ R)(L- R)
(LOnly)
CheckForSeparation.Minimum
RightOutput.
NOTE: DoNotReadjustControlR303AfterStep48.
CERAMICFILTERS
COLOR
CODE NOMINALCENTER FREQUENCY FREQUENCY
RANGE
Black 10.64MHz 10.61to10.67MHz
Blue 10.67MHz 10.64to10.70MHz
Red 10.70MHz 10.67to10.73MHz
Orange 10.73MHz 10.70to10.76MHz
White 10.76MHz 10.73to10.79MHz
13

RF, IFANDMPXALIGNMENTPROCEDURE
FORMODELMC7051
STEP CONNECT
GENERATOR
TO DUMMY
ANTENNA
CONNECT
VTVM/
SCOPETO
INPUT
SIGNAL
FREQ. SETDIAL
TO ADJUST PURPOSE
VOLTAGEREGULATORADJUSTMENT
CAUTION: RegulatorMustBeAdjustedForCorrectB+Voltage.
1 - - VTVM
Pin505 --R509 AdjustFor+33V.
AUDIOOUTPUTIDLECURRENTADJUSTMENT
CAUTION: OutputStagesMustBeAdjustedForProperIdleCurrentUnderNoSignal
ConditionsBeforePerformingOtherAdjustmentsOrAlignment.
2 VTVM
Across
R1418
NoSignal
Input R1409 AdjustControlsfor8 m V Across
CorrespondingResistors.This
WouldEqualApproximately
16mA.
3 Across
R1468
NoSignal
Input
R1459
AdjustControlsfor8 m V Across
CorrespondingResistors.This
WouldEqualApproximately
16mA.
AMALIGNMENT- PREFERREDMETHOD- WITHAMSWEEPGENERATOR
NOTE: ForAMIFAlignmentUseAMSweepSignalGeneratorOf10KHzDeviation,60HzModulationForFullBandpassDisplay.Bandswitch
InAM.AlsoConnectModulationFrequencyToScopeHorizontal.(IfAMSweepNotAvailable,SeeSteps17Through31.)
4 ShortC1J(AMGangAntennaSection)ToChassisGround.
5 TestPoint"K"
AMIF Input
Generator
Output
Probe"A"
Scope
Detector
Output
AcrossR110
+455KHz Gang
Closed -AdjustGeneratorToCenter
FrequencyOfCeramic Filter.
6
TestPoint"K"
AMIF Input
Generator
Output
Probe"A"
Scope
Detector
Output
AcrossR110 TuneGeneratorToCenterTotalBandpass
Waveform.DoNotChangeGeneratorFrequency
ForRemainderOfAMIFAlignment.
AdjustGeneratorToCenter
FrequencyOfCeramic Filter.
7
TestPoint"K"
AMIF Input
Generator
Output
Probe"A"
Scope
Detector
Output
AcrossR110
Center Freq.
OfCeramic
FilterInT102
Gang
Closed
L103, L104
(T102) AdjustForMaximumGainAnd
Symmetry.
8
TestPoint"K"
AMIF Input
Generator
Output
Probe"A"
Scope
Detector
Output
AcrossR110
Center Freq.
OfCeramic
FilterInT102
Gang
Closed
T101 AdjustForMaximum.
9 RemoveShortBetweenC1JAndChassisGround.
10 OneTurnLoosely
CoupledToAM
Wavemagnet
Antenna
None Scope 1400KHz 1400KHz C1K SetOscillatorToDialScale.
1 1
OneTurnLoosely
CoupledToAM
Wavemagnet
Antenna
None
Detector
Output
AcrossR 1 1 0
600KHz 600KHz L102
SetOscillatorToDialScale.
12
OneTurnLoosely
CoupledToAM
Wavemagnet
Antenna
None
Detector
Output
AcrossR 1 1 0 RepeatSteps
1 0 & 11ForMinimumChange.
SetOscillatorToDialScale.
13
OneTurnLoosely
CoupledToAM
Wavemagnet
Antenna
None
Detector
Output
AcrossR 1 1 0 1400KHz 1400KHz C1J AlignAntennaStage.
14
OneTurnLoosely
CoupledToAM
Wavemagnet
Antenna
None
Detector
Output
AcrossR 1 1 0
600KHz 600KHz L101If
Necessary
AlignAntennaStage.
15
OneTurnLoosely
CoupledToAM
Wavemagnet
Antenna
None
Detector
Output
AcrossR 1 1 0
RepeatSteps13& 14ForMinimumChange.
AlignAntennaStage.
16
OneTurnLoosely
CoupledToAM
Wavemagnet
Antenna
None
Detector
Output
AcrossR 1 1 0
1000KHz 1000KHz R106 AdjustForA ReadingOf4 To5
OnMeterM102WithInputOf
74dBV(5mV).
AMALIGNMENT- ALTERNATEMETHOD- IFAMSWEEPGENERATORISNOTAVAILABLE
NOTE: ForAMIFAlignmentUseA SignalWith400HertzModulation.BandswitchInAM.
17 ShortC1J(AMGangAntennaSection)ToChassisGround.
18 TestPoint"K"
AMIFInput
Generator
Output
Probe"A"
VTVM
Detector
Output
AcrossR 1 1 0
+455KHz Gang
Closed —
19
TestPoint"K"
AMIFInput
Generator
Output
Probe"A"
VTVM
Detector
Output
AcrossR 1 1 0 RockGeneratorWhileAdjustingL103
(T102Primary)ForMaximum. AdjustForMaximum.
20
TestPoint"K"
AMIFInput
Generator
Output
Probe"A"
VTVM
Detector
Output
AcrossR 1 1 0
RockGeneratorWhileAdjustingL104
(T102Secondary)ForMaximum.
AdjustForMaximum.
21
TestPoint"K"
AMIFInput
Generator
Output
Probe"A"
VTVM
Detector
Output
AcrossR 1 1 0
RepeatSteps19& 20ForMinimumChange.
AdjustForMaximum.
22
TestPoint"K"
AMIFInput
Generator
Output
Probe"A"
VTVM
Detector
Output
AcrossR 1 1 0
EqualOutputShouldBeFoundIfGenerator
IsDetunedEqualFrequencyEachSide
Maximum.
AdjustForMaximum.
23
TestPoint"K"
AMIFInput
Generator
Output
Probe"A"
VTVM
Detector
Output
AcrossR 1 1 0
Center Freq.
OfCeramic
FilterInT102
Gang
Closed T101
AdjustForMaximum.
24 RemoveShortBetweenC1JAndChassisGround.
25 OneTurnLoosely
CoupledToAM
Wavemagnet
Antenna
None VTVM 1400KHz 1400KHz C1K SetOscillatorToDialScale.
26 OneTurnLoosely
CoupledToAM
Wavemagnet
Antenna
None
Detector
Output
AcrossR110
600KHz 600KHz L102
SetOscillatorToDialScale.
27
OneTurnLoosely
CoupledToAM
Wavemagnet
Antenna
None
Detector
Output
AcrossR110 RepeatSteps26& 27ForMinimumChange.
SetOscillatorToDialScale.
28
OneTurnLoosely
CoupledToAM
Wavemagnet
Antenna
None
Detector
Output
AcrossR110 1400KHz 1400KHz C1J AlignAntennaStage.
29
OneTurnLoosely
CoupledToAM
Wavemagnet
Antenna
None
Detector
Output
AcrossR110
600KHz 600KHz L101If
Necessary
AlignAntennaStage.
30
OneTurnLoosely
CoupledToAM
Wavemagnet
Antenna
None
Detector
Output
AcrossR110
RepeatSteps29& 30ForMinimumChange.
AlignAntennaStage.
31
OneTurnLoosely
CoupledToAM
Wavemagnet
Antenna
None
Detector
Output
AcrossR110
1000KHz 1000KHz R106 AdjustForA ReadingOf4 To5
OnMeterM102WithInputOf
74dBV(5mV).
14

RF, IFANDMPXALIGNMENTPROCEDURE
FORMODELMC7051- Cont'd.
STEP CONNECT GENERATOR
TO DUMMY
ANTENNA
CONNECT
VTVM/
SCOPETO
INPUT
SIGNAL
FREQ.
SETDIAL
TO ADJUST PURPOSE
FMALIGNMENT
Note: ForFMIFAlignmentUseA SignalOf250KHzDeviation,50HertzModulationForFullBandpassDisplay.BandswitchInFM.PresetR208,
R211 AndR303ToMidRotationBeforeConnectingGenerator.ConnectGeneratorCableGroundToGangFrame.
32 ShuntC1BToGroundWithA .001MFCapacitor.
33 TestPoint"D"
FMIFInput
AtHighSide
OfC1F
Generator
Output
Probe"A"
Scope
Detector
Probe"C"
TestPoint
AtIC201
Pin1.
10.7MHz Gang
Closed AlignI.F.TransformerFor
MaximumOutputAndSymmetry
AsIndicatedInScopePattern"A".
34
TestPoint"D"
FMIFInput
AtHighSide
OfC1F
Generator
Output
Probe"A"
Scope
Detector
Probe"C"
TestPoint
AtIC201
Pin1.
TuneGeneratorToCenterTotalBandpass
Waveform.DoNotChangeGeneratorFrequency
ForRemainderOfFMIFAlignment.
AlignI.F.TransformerFor
MaximumOutputAndSymmetry
AsIndicatedInScopePattern"A".
35
TestPoint"D"
FMIFInput
AtHighSide
OfC1F
Generator
Output
Probe"A"
Scope
Detector
Probe"C"
TestPoint
AtIC201
Pin1. Center
Freq.
OfCeramic
FiltersY201,
Y202, Y203
Gang
Closed T1
AlignI.F.TransformerFor
MaximumOutputAndSymmetry
AsIndicatedInScopePattern"A".
36 TestPoint"A"
FMAntennaPost
(DisconnectAntenna)
300Ohm Scope
TestPoint
"H"
98MHz 98MHz R216 AdjustForNoSoundOutput
WhenInputIsBelow 1.7/iV With
MuteSwitchON.
37
TestPoint"A"
FMAntennaPost
(DisconnectAntenna)
300Ohm Scope
TestPoint
"H"
98MHz 98MHz
R215 AdjustForA ReadingOf4 To5
OneMeterM102WithInputOf
60dBV(1mV).
NOTE: ForFMDetectorAlignmentUseA SignalOf75KHzDeviation,1 KHzModulation.AlsoConnectGeneratorModulationFrequencyTo
ScopeHorizontal.AdjustGeneratorIFFrequencyToCenterTotalBandpassWaveform.DoNotChangeGeneratorIFFrequencyFor
RemainderOfIFAlignment.(IfYourGeneratorDoesNotProvideOutputForAudioModulationFrequencyUseHorizontalOutputFrom
Generator,OrScopeHorizontalSweep,AndFollowStep38C).MinimumDistortionCanOnlyBeAchievedByUseOfStep38ABelow.
38
TestPoint"D"
FMIFInput
AtHighSide
OfC1F
Generator
Output
Probe"A"
A.Distortion
Analyzer
(ThruA 100
UseeDe-
emphasis
Network)
Probe"B"
AndScope.
B.Scope
C.Scope
Center
Frequency
OfCeramic
FiltersY201,
Y202, Y203.
Gang
Closed
L204, L205
(T201) A.PreferredMethod:Distortion
AnalyzerAtTestPoint"H"
ShouldReadMinimumDistortion.
B.AlternateMethod:AdjustFor
LinearScopeTrace-NoCurveAtEnds
OfTrace.DisregardMeterReading.
C.AlternateMethod:AdjustFor
MaximumLengthAndSymmetry,
SimilarToScopePattern"A".
39
TestPoint"D"
FMIFInput
AtHighSide
OfC1F
Generator
Output
Probe"A"
TestPoint
"H"
Center
Frequency
OfCeramic
FiltersY201,
Y202, Y203.
Gang
Closed
L205 AdjustForCenterReadingOn
TuningMeterM101.
40 TestPoint"A" 300Ohm 106MHz 1 06MHz C1H SetOscillatorToDialScale.
41 FMAntennaPost
(DisconnectAntenna)
300Ohm
90MHz 90MHz L7
SetOscillatorToDialScale.
42
FMAntennaPost
(DisconnectAntenna)
300Ohm
RepeatSteps40& 41ForMinimumChange.
SetOscillatorToDialScale.
43
FMAntennaPost
(DisconnectAntenna)
300Ohm
106MHz 1 06MHz
C1D, C1F AlignFMDetectorStageFor
Maximum.
44
FMAntennaPost
(DisconnectAntenna)
300Ohm
90MHz 90MHz L3, L4
AlignFMDetectorStageFor
Maximum.
45
FMAntennaPost
(DisconnectAntenna)
300Ohm
106MHz 106MHz C1B AlignFMAntennaStageFor
Maximum.
46
FMAntennaPost
(DisconnectAntenna)
300Ohm
90MHz 90MHz L2IfNecessary
AlignFMAntennaStageFor
Maximum.
47
FMAntennaPost
(DisconnectAntenna)
300Ohm
RepeatSteps43Thru46ForMinimumChange.
48 AudioOsc. — TestPoint
"F"
200KHz T301 AlignForMinimum.
49 TestPoint"H"
— TestPoint
"F"
200KHz
T302
AlignForMinimum.
NOTE: ApplySufficientSignalLevel— Approx. 1 00Microvolts— ToObtainFullLimitingAtPointNear98MHz.
50 Frequency
CounterAnd/
OrScope
TestPoint
"M"
Unmodulated
RFCarrier R308 A.FrequencyCounterShould
Read19KHz,+ 100Hz.
B.AlternateMethod:ConnectTest
Point"M"SignalToScopeVertical
AndAnAccurate19KHzSignal
ToScopeHorizontalInput.Adjust
ForOneSquareSynchronized
Waveform.
51
ScopeAnd/Or
ACVTVM
LeftTape
Output
98MHz
10%Pilot
(L+R)(L-R)
(LOnly)
R318 AdjustForSeparation.
MaximumLeftOutput.
52 RightTape
Output.
98MHz
10%Pilot
(L+R)(L-R)
(LOnly)
— CheckForSeparation.Minimum
RightOutput.
NOTE: DoNotReadjustControlR308AfterStep50.
CERAMICFILTERS
COLOR
CODE NOMINALCENTER FREQUENCY FREQUENCY
RANGE
Black 10.64MHz 10.61to10.67MHz
Blue 10.67MHz 10.64to10.70MHz
Red 10.70MHz 10.67to10.73MHz
Orange 10.73MHz 10.70to10.76MHz
White 10.76MHz 10.73to10.79MHz
15

DISASSEMBLYPROCEDURES
FIGURE 1 - MODEL MC7041 - FRONT VIEW
CHASSISACCESS
Accesstomostareasofthechassiscanbeachievedbyremoval
ofthecabinettopandthebottomcover(SeeFigures1 and2).
Numbersinparenthesis( ) correspondtothenumbersshown
onexplodedviewsandotherillustrations.
CABINETTOPREMOVAL
1. Removetwoscrews(83onMC7031and82onMC7041)
andtheircupwashers(58)locatedoneachsideofthe
cabinet(1).
2. Liftcabinet(1)upwardfromchassis.
CHASSISBOTTOMCOVERREMOVAL
1. Removeninescrews(82onMC7031and81onMC7041)
frombottomcover(2).
NOTE: Itisnotnecessarytoremovethefourscrews
(81onMC7031and80onMC7041)holdingthe
fourfeet(59onMC7031and87onMC7041).
2. Whenremovingbottomcover(2)notethatthefrontedge
ofbottomcovermustbeinsertedunderlipoffrontframe
whenitisreinstalled.
FRONTPANEL(ESCUTCHEONREMOVAL)
Certaincomponentsalongthefrontedgeofthechassiscanbe
reachedonlyafterthefrontpanel(3)hasbeenremoved:
1. Loosenthealienscrew(recessedintuningknobassembly)
holdingtuningknobassembly(6)totuningshaft(18on
MC7031and20onMC7041).
2. Removetuningknobassemblyfromshaft.
3.Removeremainingknobsbypullingoutward.
4.Removefivescrewsfromthefrontpanel(3).
a.Threescrews(74onMC7031and77onMC7041)
arelocatedonthebottom.
b.Twoscrews(72onMC7031and86onMC7041)
arelocatedonthetop.
5.Removefrontpanel(3)bypullingoutwards.
FIGURE 2 - MODEL MC7041 - BACK VIEW
16

DIALLIGHTREPLACEMENT
Fourwedgebasetypelamps(DS501throughDS504)are
usedinthesemodels.Theymaybereplacedinthefollowing
manner.
1. Removecabinettop(1)asexplainedabove.
2. Lampsaremountedingrommets(60onMC7031and21
onMC7041).
3.Removegrommetandlamp.
4.Lampissolderedtoleadswithingrommet.
5.Carefullypulllampoutofgrommet.
6.Unsolderlampleadsandremovelamp.
7.Soldernewlamptoleads.
8.Presslampintogrommet,beingcertainthatitisfully
seated.
9. Pressgrommetfirmlyintolightreflector(23onMC7031
and22onMC7041),usinga twistingmotionuntilitis
secure.
10. Becertainthatleadsaredressedawayfromthedialcord.
17
FIGURE 3 - MODEL MC7041 - CHASSIS VIEW
FIGURE 4 - MODEL MC7051 - FRONT VIEW

REMOVEFIVESCREWS(76)
REMOVEONESCREW(76)
ANDWASHER(29)
REMOVENINESCREWS(76)
REMOVETWOSCREWS(79)ANDCUPWASHERS(49)ONEACHSIDE
FIGURE 5 - MODEL MC7051 - BACK VIEW
MODELMC7051
CHASSISACCESS
Accesstomostareasofthechassiscanbeachievedbyremoval
ofthecabinettopandthebottomcover(SeeFigures4 and5).
CABINETTOPREMOVAL
1. Removetwoscrews(79)andtheircupwashers(49)
locatedoneachsideofthecabinet(1).
2. Liftcabinet(1)upwardfromchassis.
CHASSISBOTTOMCOVERREMOVAL
1. Removefourteenscrews(76)frombottomcover(2).
2. Removeonescrew(76)andmetalwasher(29)located
nearcenterofbottomcover(1).
NOTE: Itisnotnecessarytoremovethefourscrews(77)
holdingthefourfeet(48).
FRONTPANEL(ESCUTCHEON)REMOVAL
Certaincomponentsalongthefrontedgeofthechassiscanbe
reachedonlyafterthefrontpanel(3)hasbeenremoved:
1. Removecabinet(1)asabove.
2. Loosenthealienscrew(recessedintuningknobassembly)
holdingtuningknobassembly(15)totuningshaft(24).
3.Removetuningknobassembly(15)fromshaft(24).
4.Removeremainingknobsbypullingoutward.
5.Removefivescrewsfromthefrontpanel(3).
a.Threescrews(82)arelocatedonthebottom.
b.Twoscrews(74)arelocatedonthetop.
6.Removefrontpanel(3)bypullingoutwards.
CONTROLCIRCUITBOARDREMOVAL
Mostcustomeroperatingcontrolsaremountedononecircuit
boardassembly(98)locateddirectlybehindthefrontpanel(3).
Proceedasfollows:
1. Removethecabinettop(1),bottomcover(2)andfront
panel(3)asexplainedabove.
2. Removemaskingstrips(27,28)fromtheeighttoggletype
controllevers.
3.Releaseinterconnectingwiresandcablesfromthreewire
retainingclips(40,41)ontopofchassisandfromone
clip(34)onbottomofchassis(adjacenttocircuitboard).
4.Removefourscrewsfromfrontchassisframe(5).
5.Slidecontrolchassisassemblytorearanddownwarduntil
itclearsfrontchassisframe(5).
6.Reinstallcontrolchassisassembly,reversingtheabove
procedure.
NOTE: Whenreinstallingthecontrolchassisassembly,slide
theendnearestthetuningcontrolinwardfirst.
DIALLIGHTREPLACEMENT
Fivewedgebasetypelamps(DSX501throughDSX505)
areusedinthismodel.Theymaybereplacedasfollows:
(SeeFigure6):
1. Removecabinettop(1)asexplainedabove.
2. Twistlampsocket(101)counterclockwiseandremove
lampsocket(101)withlamp.
18