Zenith MC7031, MC7041, MC7051 Service Manual

SERVICE MANUAL

MODELS

HF-46

22.8M-CPC

STEREO RECEIVERS

MC7031, MC7041,

ZENITH

PARTS

11000 SEYMOUR AVENUE. FRANKLIN PARK. ILLINOIS

RADIO CORPORATION

AND SERVICE DIVISION

JUNE,

PRINTED

1980

IN

U.S.A.

MC7051

MODEL MC7051

ILLUSTRATED

60131

$4.00

923-972

To the Service Technician

PRODUCT

CAUTION: Service work should familiar lines. injury

No

with

To

do

to the

SAFETY

modification

all

of

the otherwise increases user.

of any

be

performed only

following safety checks

SERVICING GUIDELINES

the

SAFETY CHECKS

SUBJECT: Fire & Shock Hazard

1.

Be

sure that to avoid possibility is especially important ported

2 Always replace

and barriers after working

3. Check cord. and replace

4

All

fuses

of

the agrams Zenith types

5 After re-assembly

age test such set

is

all

components

of

adjacent components shorts. This

on

those chassis which

to and

from

the

repair shop.

all

protective devices such

on a

for

frayed insulation

Also check across-the-line components

if

necessary.

and

certain resistors

flameproof type (shaded

and

parts lists) must

to

prevent potential fire hazard.

of the set

on the

as the

safe

exposed metallic parts

knobs, antenna terminals,

to

operate without danger

circuit should

after

risk

of

are

positioned

receiver.

on

wires including

and

on the

be

replaced with exact

always perform

be

you

and

servicing guide-

potential

in

capacitors which

schematic

of the

etc. to be

of

electrical shock.

attempted.

are

thoroughly

hazards

such

are

as

insulators

the AC

for

damage

an AC

cabinet

sure

FOR ALL

and

a way

trans-

are di-

leak-

the

AUDIO AMPLIFIERS

Do

not use a

an

AC sitivity watt resistor, (63-10401-76) paralleled type capacitor (22-4384) between a known good earth ground (water pipe, conduit, lic parts, the combination itor. Reverse age measurements age measured must responds limit constitutes a potential shock hazard corrected immediately.

line isolation transformer during this test.

voltmeter having 5000 ohms

in the

following manner: Connect

one at a

to 0.5

good earth ground such

as the

pipe,

conduit,

time. Measure

1500 ohm

the AC

milliamp

water

etc.

AND

RADIO RECEIVERS

per

volt

or

more

a 1500 ohm 10

by a .15 mfd, AC

etc.) and the

the AC

resistor

plug

on the set and

for

each exposed metallic part. Volt-

not

exceed

0.75

AC. Any

AC VOLTMETER

exposed metal-

voltage across

and .15 mfd.

repeat

volts

RMS.

value exceeding this

and

place this probe on each exposed metallic part.

Use

sen-

capac-

AC

volt-

This cor-

must

be

TABLE

OF

Safety Servicing Guidelines and Technical Applications Index Inside Front Cover Index Product Features Pages

Record Changer Features Page Tape Unit Features Page Introduction Page Product Features Page

General Information Page Alignment Procedures Pages Disassembly Pages Theory Parts Lists Pages 24-36 Integrated Circuit Block Diagrams Pages Schematic, Related Drawings and Exploded Views Pages 43-60

CONTENTS

to

Schematics and Related Drawings Page

and

Application Pages 20-22

1

2-5

6 7 8 9

10 11-15 16-19

38-41

TECHNICAL APPLICATIONS INDEX Various introduced into Such information has been included

HF

HF HF

"HF"

series service manuals contain information relating

our

products.

18:

Theory - Diodes (Including Zener and SCR), Transistors, (PNP, NPN, Darlington, and JFET). Applications - Chassis 29AT24 (JFET FM-RF,

Multiplex, Electronic Touch Switching), Complementary Symmetry, Chassis 11ZT27 (Electronic Filter).

22:

Theory - JFET, IGFET, MOSFET, Applications - Dual Gate MOSFET FM-RF, JFET Biplex Detector, Quasi-Complementary Symmetry.

HF

23:

Applications - Model C9029/Chassis 15WCA10 Four Channel Decoder.

HF

26:

Applications - Chassis 15WDR51 (JFET Meter Circuit, Multiplex

HF

27:

Applications - Model SD2568 Speaker Switching Circuitry.

28:

Applications - Model D9013W Allegro Speaker System.

29:

Theory — Light Emitting Diodes (LED). Applications - Three Light Tuning (Target Tuning), Multiplex HF 29S1: Applications — Snap-off Escutcheon HF

30:

Applications — Snap-off Escutcheon HF 31: Theory

HF 32S2: Applications - Four Channel Sound Reproduction Input

HF

32:

HF33:

Theory

HF 33S1: Applications — "J" Line Allegro Speaker System Repair Procedures. HF

34:

HF

39:

and

General Product Information — Audio Circuitry (including

Procedures.

Inter Changeability, Chassis 12WGR59 Accessibility.

Applications

Line Allegro Speaker Systems and Repair Procedures.

General Product Information — Audio Circuitry (including Output

Applications —

Applications

Applications - Chassis 12WGR59 (Ceramic Filters,

- "H"

and

Applications - Chassis 3WJR52 (Ceramic Filters,

"K"

- "K"

In

addition, service procedures

in the

following service manuals:

and Out

Line Disassembly Procedures, Part Number Identification, Record Changer

Line Allegro Speaker Systems

Front Chassis Removal,

Vs.

and

Repair Procedures. General Product Information.

and

Repair Procedures.

to

solid state device theory, operation

are

also explained,

IC,

Four Channel Decoding).

"E"

Line Models.

"F"

IF IC,

Two on Two

Output, Repairing Push Button Switches, Record Changer

IF IC's for AM and FM

Line Models.

Quadrature Detector, Interstation Muting,

Speaker Matrix, Allegro Speaker Systems),

IC),

"J" Line Disassembly Procedures.

if

required,

Quadrature Detector,

in the

IC.

and

Phono Cartridge Inter

and

appropriate service manuals.

circuit applications

PLL

Multiplex

"G"

Line Disassembly

and

Phono Cartridge

Changeability,

PLL

Multiplex

IC,

as

Audio).

"H"

Audio).

INDEX

*REFER TO MASTER INDEX FOR UPDATED INFORMATION

CHASSIS

OR MODEL ON PAGE CONTAINED IN OR MODEL

1WEA10 (Z1) 1WEA11 (Z1) 1WGR50 1WJR55

3WEA10 (ZD

3WGR50 3WHR50 3WJR50,50Z 3WJR51,51Z 3WGR52 3WHR52 3WJR52,52Z 3WGR54 3WR10X 3WR11X 3WR12X 5WER50 5WFR50 5WER51

5WFR51 5WER52 5WER52Z1 5WER52Z2 5WER52Z3 5WER53 5WFR53 6WGR55 6WHR55 6WGR56 6WHR56 6WGR57 6WHR57 6WGR90 6WGR91 8WJR56 8WJR57

12WGR58

12WGR59

12WHR29

15WJR29

15WEA10

15WFR51

15WER55

15WFR55

15WER56 15WFR57

35WFR50 G1000W H1000W,W1,W2,W3 J1000W1,W2 G2000W G2000W11 H2000W,W3 J2000W1,W2 G3000W G3000W11 H3000W,W3

HF 28S1 is Part No. 923-734 HF30 is Part No. 923-809 HF31S2 is Part No. 923-864 HF33S1 is Part No. 923-921 HF34 is Part No. 923-927 HF 37 is Part No. 923-942 HF 38 is Part No. 923-943 HF 39 is Part No 923-944 HF40 is Part No. 923-945

HF41 is Part No. 923-962

HF45 is Part No. 923-971 HF46 is Part No. 923-972

INFORMATION

-

PRIOR DATA

HF

28S1,

29, 30

HF

28S1,

29, 30 HF 31S1.31S2 HF 33, 33S1 HF 29, 29S2, 30 E9014X (1) HF 31.31S1 HF 32, 32S1 HF 33,

33S1,

34 G9019W HF 33, 33S1 E9026W HF

31,

31S1 HF32S1 HF 33.33S1 HF

31,

32S1 HF40,

47 HF40.47 HF40,

47 HF 28S1,29,29S1,30,30S1 HF 30,

31S1,

31 HF 29, 29S1, 30,30S1 IS4061-2 HF 30.30S1 HF 29S2, 30, 30S1 HF 30, 30S1 HF 30, 30S1 HF 30, 30S1 IS4081-1 HF 29,

29S1,

30 IS4081-2 HF 30, 30S1 HF

31,

31S1 HF 32, 32S1 MC1000-11 HF 31,31S1 MC1000-12 HF 32, 32S1

HF

31,

31S1 MC2000-11

HF 32.32S1 MC2000-12 HF 31S1 HF 31S2 HF 33 HF 33 HF

31,

32S1 MC4000-11

HF

31,

31S1 MC4000-12

HF 32, 32S1 HF 33,

33S1,

34

HF

29S1,

30 MC6060 HF 30, 30S1 MC6060-1 HF 29,29S1,29S2,30,30S1 MC6065 HF 30, 30S1 HF 29, 29S1, 29S2, 30 HF 30, 30S1 HF 30,

30S1,

32S1 HF31./31S1 HF 32 HF33 HF

31,

31S1 HF 31S1 HF 32 HF 33 HF 31,31S1 HF 31S1 HF 32

HF 29 is Part No. 923-740 HF 29S1 is Part No. 923-762 HF 30S1 is Part No. 923-841 HF 31 is Part No. 923-848 HF32 is Part No. 923-874 HF 32S1 is Part No. 923-895

HF42 is Part No. 923-966

CHASSIS INFORMATION PRIOR DATA

J3000W1

E9012W (1) G9012W1 E9014W (1)

G9014W E9018WO)

E9029W

IS4020 IS4021 IS4030

IS4031 IS4040 IS4041 IS4060 IS4061-1

IS4070 IS4071-1 IS4071-2 IS4080

IS4081-3 MC1000

MC2000

MC3000 MC3000-11 MC3000-12 MC4000

MC6010 MC6020

MC7030 MC7031 MC7040 MC7041 MC7050 MC7051 8 to 60 MC9020 MC9025 MC9030 MC9035 MC9040 MC9050 MC9070 MC9070-1

HF 35 is Part No. 923-933

HF43 is Part No. 923-967 HF 47 is Part No

ON PAGE

8 to 60

927973 HF 48 is Part No. 923-974

—

-

—

-

_

_ _

-

- -

-

- -

-

- -

-

HF 33 HF HF HF HF HF 31S1 HF HF 31.31S1 HF 30S1 HF 29S1

HF35 HF41 HF35 HF41 HF35 HF41 HF36 HF42 HF43 HF36 HF42 HF43 HF36 HF42 HF43 HF44 HF39 HF39

HF 39

HF39

HF 39

HF37

HF45

HF 37

HF37S1 HF45

HF 38

RC 28

RC33

RC 29

RC 34 RC30 RC37

TR 41 TR 41S1

HF29S2 is Part No. 923-784 HF 31S1 is Part No. 923-857 HF 33 is Part No. 923-901 HF 36 is Part No. 923-934

HF44 is Part No. 923-970

CONTAINED IN

29S1,

30

31,

31S1

29S1,

30

29S1,

30

29S1,

30

-

1

PRODUCT

FEATURES

CABINET

MODEL

IS4021

IS4031 Walnut

IS4041

IS4061-1

IS4061-2

IS4071-1

IS4071-2

IS4081-1

IS4081-2

IS4081-3

IS4090

L900P

LR902P

LR902P1

LR912AE

LR915P

COLOR

Walnut

Pecan

Antique Oak

Pecan

STYLE

NOTE

M, D

C, LL

•

REFER

MODEL TYPE

A

3WR10X AM/FM/FM

3WR11X AM/FM/FM

3WR11X

3WR11X AM/FM/FM

3WR11X

TO

CHASSIS SPEAKERS

-

—

AM/FM/FM Stereo/Phono/ Tape

Stereo/Phono/ Tape

AM/FM/FM Stereo/Phono/ Tape

Stereo/Phono/ Tape

AM/FM/FM Stereo/Phono/ Tape

SEE NOTES

PAGE

ONE

INDEX

NUMBER

49-1153-02 49-1094-01

49-1261-02 49-1251-02

PART

Note

FOR

D2

ON

IMPED.

Ohms)

PAGE

MODELS

AND

(In

-

—

16

45

16

45

16

45

8 8

5

IN

THIS MANUAL

RECORD

CHANGER

QTY.

Inches)

-

—

2-6x9 2-31/

2-6x9 2-3 %

2-6x9 2-31/

2-8 2-3

SIZE

2

NUMBER

NOTE

169-573

169-579

169-573-01

169-581

PART

B

•

OTHER FEATURES

TAPE

PROVISION

NOTE

8TK-R/P 969-51

CASS-R/P 969-52

CASS-R/P 969-52 8TK-R/P 969-51

8TK-R/P 969-55

8TK-R/P 969-51

CASS-R/P 969-56

CASS-R/P 969-56 8TK-R/P 969-55

CASS-R/P 969-56 8TK-R/P 969-51

CASS-R/P A-8051 8TK-R/P A-7021

CASS-R/P 969-62

8TK-P 969-60

8TK-R/P 969-51

PROVISION

C

SPEAKER

NOTE A1,

A2,

SPKAB

A1,

A2,

SPKAB

A1,

A2,

SPKAB

A1,

A2,

A3,

A4,

SPKOAB

A1,

A2,

A3,

A4,

SPKOAB

A1,

A2,

A3,

A4,

SPKOAB

A1,

A2,

A3,

A4,

SPKOAB

A1,

A2,

A3,

A4,

SPKOAB

A1,

A2,

A3,

A4,

SPKOAB

A1,

A2,

A3,

A4,

SPKOAB

A1,

A2,

A3,

A4,

SPKOAB

A1,

A2,

SPK

A1,

A2,

SPK

A1,

A2,

SPK

A1,

A2,

SPK

A1,

A2,

SPK

NOTE

D

AUX, DL, H, HIF, TO

AUX, DL, F, H, HIF, LD,

LOF,

MU, AUX, DL, F,

H, HIF, LD, LOF, MU,T, TO

AUX, DL, F, H, HIF, LD, LOF, MU,T, TO

AUX, DL, F, H, HIF, LD, LOF, MU,

AUX, DL, F, H, HIF, LD, LOF, MU,T,TO

AFC, DL,

H, HIF,

T,TO

AFC, DL,

H, HIF,

RS,

T, TO

AFC, DL,

H, HIF,

RS,T,TO A, AFC,

AUX, DL, H, HIF, TO

A, AFC, AUX, DL, H, HIF, TO

MISC.

E

LD, T,

MS,

T, TO

MS,

T, TO

MS,

AUX,

RS,T,

2

PRODUCT

FEATURES

CABINET

MODEL

LR915P1 Pecan

LR915P2

LR916PN Pine

LR916PN1

LR917M Pecan

LR919P

LR919P1 Pecan

LR920AE

MC1000 Walnut

MC1000-11

MC1000-12 Walnut

MC2000 Walnut

MC2000-11 Walnut

MC2000-12 Walnut

MC3000 Walnut

MC3000-11 Walnut

MC3000-12 Walnut

COLOR

Pecan

Pine

Pecan

Antique Oak

Walnut

STYLE

NOTE

C,

LL

C,

LL

C,

LL

C,

LL

C,

LL

C,

LL

C,

LL

C,

LL

M, SP

M,

SP

M,

SP

M,

SP

M,

SP

M,

SP

M,

SP

•

REFER

MODEL

A

3WR11X AM/FM/FM

3WR11X

3WR11X AM/FM/FM

3WR12X AM/FM/FM

3WR12X

TO

CHASSIS

Stereo/Phono/ Tape

AM/FM/FM Stereo/Phono/ Tape

Stereo/Phono/ Tape

AM/FM/FM Stereo/Phono/ Tape

—

— —

—

SEE NOTES

PAGE

ONE

TYPE

—

INDEX

NUMBER

49-1261-02 49-1251-02

49-1261-02

49-1251-02

49-1261-02 49-1251-02

49-1217-01 49-1166-01

49-1277 49-1278

49-1277 49-1278-02

49-1277 49-1278

49-1293 49-1261-02

49-1166-01 49-1293 49-1261-02

49-1166-01 49-1290

49-1288-01

49-1290 49-1288-01

FOR

PART

or

ON

PAGE

MODELS

SPEAKERS

IMPED.

(In

Ohms)

8 8

8 8 8

8 8

8

8 8

5

IN

THIS MANUAL

QTY.

AND

SIZE

(In

Inches)

2-8 2-3

2-10 2-3%

1-61/

2

1-2

1

-61/

2

1-2

1-61/

2

1-2

1-8 1-8

1-31/* 1-8 1-8

1-31/

2

1-8 1-8

1

-3%

1-10 1-31/

2

1-10 1

-31/

2

1-10 1

-31/

2

•

RECORD

CHANGER

PART

NUMBER

NOTE

169-570

169-581

169-570

169-581

169-586

169-571 8TK-R/P

169-586

B

PROVISION

NOTE

8TK-R/P 969-51

969-51

8TK-R/P 969-51

—

— —

—

OTHER FEATURES

—

PROVISION

C

SPEAKER

NOTE

D

A1,

A2,

SPK

A1,

A2,

SPK

A1,

A2,

SPK

A1,

A2,

SPK

A1,

A2,

SPK

A1,

A2,

SPK

A1,

A2,

SPK

A1,

A2,

SPK

20

Watt Handling Capability

20

Watt Handling Capability

20

Watt Handling Capability

40

Watt Handling Capability

40

Watt Handling Capability

40

Watt Handling Capability

60

Watt Handling Capability

60

Watt Handling Capability

60

Watt Handling Capability

TAPE

—

NOTE

A,

AFC AUX, HIF, TO

A,

AFC, AUX, HIF, TO

A,

AFC, AUX, HIF, TO

A,

AFC, AUX, HIF, TO

A,

AFC, AUX, HIF, TO

A,

AFC, AUX, HIF, TO

A,

AFC, AUX, HIF, TO

A,

AFC,

AUX, HIF, TO

A1

A2

A3

MISC.

E

DL, H,

RS,T,

DL, H,

RS,T,

DL, H,

RS,

T,

DL, H,

RS,T,

DL, H,

RS,T,

DL, H,

RS,T,

DL, H,

RS,T,

DL, H,

RS,T,

3

PRODUCT

FEATURES

CABINET

MODEL

MC4000 Walnut

MC4000-11 Walnut

MC4000-12

MC6020

MC6065 Walnut

MC7031 Walnut

MC7041

MC7051

MC9020 Walnut MC9025 MC9030 Walnut MC9035 MC9040 MC9050

MC9070

MC9070-1 Walnut

SL2597P9

COLOR

Walnut

Walnut Walnut Walnut

Walnut

Pecan

STYLE

NOTE

M, SP

M

M, D M, D M, D M, D M, D M, D

M

C, 2LL

•

REFER

MODEL TYPE

A

TO

CHASSIS

- -

— —

-

- -

-

3WR12X

SEE NOTES

PAGE

ONE

AM/FM/FM Stereo/Tape

AM/FM/FM Stereo

-

- -

-

1 ape

Tape

AM/FM/FM Stereo/Phono/ Tape/Color Combo

ON

INDEX

NUMBER

49-1291 49-1289 49-1288-01

PART

Note

FOR

D2

- -

PAGE

MODELS

SPEAKERS

IMPED.

(In

Ohms)

5.5

7.0

8.0

5.5

7.0

8.0

5.5

7.0

8.0

5

IN

QTY. AND (In

Inches)

1-12

1-5

1

1-12

1-5

1-31/

1-12

1-5

1

SIZE

-31/

-

- - -

-

- - - -

-

- -

- - -

49-1276 49-1234-04 49-1166

16

8

2-10

1-5

2-H

8

THIS MANUAL

RECORD

CHANGER

PART

NUMBER

NOTE

B

- -

2

— —

2

— —

2

Note

B3

Note

B3

Note

B3

Note

B3

Note

B3

169-574 169-579 169-575 169-580 169-576

-

169-585

•

OTHER FEATURES

TAPE

PROVISION

NOTE

8TK-R/P 969-54

CASS-R/P 969-59

TM

PROVISION

C

SPEAKER

NOTE

D

100

Watt

Handling

Capability

100

Watt

Handling

Capability

100

Watt Handling Capability

A1,

A2,

SPKOAB

A1,

A2,

A3,

A4,

SPKOAB

A2,

A3, A4 SPKOAB

A3,

A4, SPKOAB

A3,

A4, SPKOAB

- -

-

- - -

CASS-R/P 969-58

CASS-R/P 969-63

8TK-R/P 969-51

- -

-

- -

-

A2,

A3, A4, SPK

MISC.

NOTE

E

A4

AFC,

AUX,

DL,

F, H,

HIF,

LD,

LOF,

MS,

MU,T,TO

AFC,

AUX,

DL,

F, H,

HIF,

LD,

LOF,

MS,

MU,

T, TO

AFC,

AUX,

DE,

DL, F,

H, HIF, LD,

LOF,

MS, MU,TIO,TM, TS,

TZ

AFC,

AUX, DE,

DL, F, H,

HIF,

LD, LOF,

MS,MU,TIO,

TM,TS,TZ

AUX, DE,DL, F, H, HIF,

LD,

LOF, MS,

MU,

2TIO,

TD,

TM, TS,

TZ

-

H

A, AFC, AUX,

DL,

H, HIF,

T, TO

4

PRODUCT

NOTES

NOTE A - CABINET STYLE: C = Console, D = Dust Cover, M = Modular, LL - Lift Lid, 2LL - Two Lift Lids, SP = Speaker System.

NOTE B - RECORD CHANGERS NOTE B1: Provision for external record changer using a ceramic cartridge. NOTE B2: Provision for external record changer using a magnetic

cartridge. NOTE B3: Provision for external record changer using either a ceramic

or magnetic cartridge. Record Changers having alpha suffixes (i.e. 169-511 A) denote variations

of internal mechanical and/or electrical components (refer to Record Changer Features charts) but otherwise are interchangeable with other alpha suffix and non-suffix versions.

NOTE C - TAPE INPUT AND OUTPUT PROVISIONS:

Factory Installed: 8 TK - Eight Track Cartridge. Cass = Cassette, P = Play, R = Record. TM = Top of Set Model for installation with the designated console or modular models:

Model MC9070 - Cassette Tape Player/Recorder.

Tape Units having alpha suffixes (ie. 169-510A) denote variations of internal mechanical and/or electrical components (refer to Tape Unit

Features chart) but are otherwise interchangeable with other alpha suffix and non-suffix versions. Units having numeric (ie. 169-506O1) or numeric/alpha (ie. 169-506-01A) suffixes may have a one way interchangeability under some conditions (refer to Product Features chart).

NOTE D - SPEAKER PROVISIONS: NOTE D1: Models E9012 series, G1000W, G2000W, W11, G3000W,

W11,

G9012W1, H3000W series, J1000W series, J2000W series and J3000W series are 8 ohm Allegro Speaker Systems. Allegro Models in the E9014 and E9018 series were 16 ohm systems.

G9014W, G9019W, H1000W series, H2000W series,

FEATURES

NOTE D2: "K" and "L" Models may use either MC1000, MC2000, MC3000 or MC4000 8 ohm Allegro Speaker Systems as indicated. (See Speaker Provisions).

A1 = Model MC1000 Allegro 1000 Speaker System may be used. A2 = Model MC2000 Allegro 2000 Speaker System may be used. A3 = Model MC3000 Allegro 3000 Speaker System may be used. A4 = Model MC4000 Allegro 4000 Speaker System may be used. SPK = Switch to select Internal (Main), External (Remote) or Both Speaker Systems. SPKAB = Switch to select A, B or Both Speaker Systems. SPKOAB = Switch to select A, B or Both Speaker Systems or to switch all Speaker Systems off.

NOTE E - MISCELLANEOUS FEATURES:

= Speaker System is Allegro.

A A1 = Speaker System is Allegro 1000.

= Speaker System is Allegro 2000.

A2 A3 = Speaker System is Allegro 3000. A4 = Speaker System is Allegro 4000.

= AFC Defeat Switch.

AFC AUX = Auxiliary input accepts certain optional Record Changers or

DE = Deemphasis Switch. DL F = Flywheel Tuning. H = Headphone Jack (Stereo). HIF = Hi Filter Switch. LD LOF = Lo Filter Switch. MS = Mono/Stereo Switch. MU PL RS T = Tuning Meter. TD = Tape Dubbing Switch. TIO TM = Tape Monitor Switch. TO TS TZ = Zero Center Tuning Meter (FM).

Tape Units listed under Notes B and C.

= Dial Scale Light.

= Loudness Switch.

= FM Mute Switch. = Power Indicator Light (other than Dial Scale Light). = Record Storage.

= Tape Input/Output. = Tape Output.

= Signal Strength Meter (AM and FM).

5

PART

NUMBER

169-570

169-571 GAR

169-573 BSR

169-573-01

169-574

169-574-01

169-575

169-575-01

169-576

169-579 TENVA

169-580

169-581

169-585 TENVA

169-586

NOTE

1 — All

NOTE

2 — D =

NOTE

3 —

NOTE

4 —

NOTE

5 —

NOTE

6—

CODE

6200C

TENVA

record changers have 120VAC 60Hz motors.

Diamond,

Stylus

and 56-641-03

Adapter 27-628

Record changers will play

MFG.

GAR

630S

C197

BSR

C197

GAR 630S

GAR

GT4

GAR

GT4

GAR

GT25

MT30

MT60

BSR

C198

MT30

BSR

C218

56-641,

CART-

RIDGE,

STYLUS

NOTE

2

PRESSURE IN GRAMS

142-199

56-643

0.7D-3.0S

3.0-5.0

142-192

56-643

0.7D-3.0S

3.0-5.0

142-197

56-639

0.7D-3.0S

3.5-5.0

142-198

56-642

0.7D-3.0S

3.5-5.0

142-194

56-641

0.6D

3.5-5.0

142-189

56-641

0.6D

3.5-5.0

142-195

56-641-02

0.4X0.7D

2.5-4.5

142-189

56-641

0.6D

2.5-4.5

142-196

56-641-03

0.4X0.7D

1.5-3.0

142-200

56-641-04

0.6D

2.0-4.0

142-195

56-641-02

0.4X0.7D

2.0-4.0

142-190

56-643

0.7D-3.0S

3.0-5.0

142-201

56-647

0.7DX3.0S

3.0-5.0

142-202

56-647

0.7D-3.0S

3.0-5.5

S =

Manufactured Sapphire.

has a 0.6 mil

are

Bi-radial Eliptical stylus.

is a

disc type

45

RPM

ADAPTER

NOTE

A-7545

or

76-2132

A-7545

or

76-2132

S-72648,

A-6616

or

A-8352

S-72648,

A-6616,

or

27-628

A-7545

or

76-2132

A-7545

or

76-2132

27-627

or

76-2132

27-627

or

76-2132

27-627

or

76-2132

76-2132 Program

A-6616

or

27-628

spherical

and

as

many

as

many

RECORD CHANGER FEATURES

SEE NOTES BELOW

4

Off, Manual,

Auto,

Off, Manual,

Auto-Repeat

Off, Manual,

tip.

76-2132

as

five (flat

as six

MODES

(TYPE)

Auto

(Slide)

Auto

(Slide)

Auto

(Slide)

Off, On,

Auto

(Slide)

Auto

(Slide)

Auto

(Slide)

Repeat

(Slide)

Automatic,

Repeat

(Rotary)

1 Through

(Slide)

Play

(Button)

Program

1 Through

(Slide)

Play

(Button)

Off, On.

Auto

Program

1 Through

(Slide)

Play

(Button)

Off, On,

Auto

56-641-01

is a

stub type. Adapter used will vary with model.

and

(flat

and

SIZE

(TYPE)

12",

7", 33 7",

10",

(Slide) 12", 33 7", 33 7", 45 10", 78 (Slide)

7,10,12

(Slide)

7,10,12

(Slide)

12",

7",

7", 45 10",

(Slide)

12",

7",

7", 10",

(Slide)

N.A.

7,

12

7,

12

(Rotary)

N.A.

6

N.A.

6

7,10,12

(Slide)

N.A.

6

7,10,12

(Slide)

is an

optional

unwarped records

6

SPEED (TYPE)

33

45

78

33,45,78

(Slide)

33,45,78

(Slide)

33 33

78 33

33 45 78

33,

45

33,

45

(Slide)

33,

45

33,

45

(Slide)

33,

45

33,

45

(Rotary)

33,

45

(Slide)

33,

45

(Slide)

Pitch

Control

(Rotary)

33,45,78

(Slide)

33,

45

(Slide)

33,45

(Slide)

2.5 mil mfg

in

12-inch, 10-inch

RECORD

STACK

Note

5

Note

5

Note

5

Note

5

Note

5

Note

5

Note

5

Note

5

Note

5

Note

5

Note

5

Note

5

Note

5

Note

5

Note

5

Note

5

Note

5

sapphire stylus

TURN-

TABLE

DIA.

10

1/2"

Metal

10

1/2"

Metal

11"

Metal

11"

Metal

10

1/2"

Metal

10

1/2"

Metal

11

1/4"

Metal

(Belt

Drive)

11

1/4"

Metal

(Belt

Drive)

11

1/4"

Metal

(Belt

Drive)

11"

Aluminum

Metal

11"

Aluminum

Metal

10

1/2"

Plastic

11"

Aluminum

Metal

10

1/2"

Plastic

or

7-inch

TURN-

BASE

TABLE

PLATE COLOR

Black Black Chrome

Black Black

Black Black Chrome

N.A. Black N.A.

Gray

Black Black N.A.

Black Black Black

Black Black N.A.

Black Black Black

for

7-inch

PAD

COLOR

Black N.A.

playing

78 RPM

size. Sizes cannot

PRES-

SURE

ARM

COLOR

and

Black

Chrome

and

Black

Black Cue

and

Black

and

Black

records. 56-641-02

MISC.

(TYPE)

(Lever)

Viscous

(Lever)

Anti-Skate

(Slide)

(Lever)

Viscous

(Lever)

Anti-Skate

(Slide)

Viscous

(Lever)

Anti-Skate

(Slide)

Viscous

(Slide)

Anti-Skate

(Rotary)

Start/Reject

(Button)

Viscous

(Slide)

Anti-Skate

(Rotary)

Start/Reject

(Button)

Viscous

(Slide)

Anti-Skate

(Rotary)

Start/Reject

(Rotary)

Damped

(Lever)

Anti-Skate

(Rotary)

Belt Drive

24 Pole Motor

Damped

(Lever)

Anti-Skate

(Rotary)

Belt Drive

Electronic Drive

And Speed

Control

24_Pple Motor

Strobe Indicator

(Lever)

Anti-Skate

(Rotary)

2 Pole Motor Damped

(Lever)

Anti-Skate

(Rotary)

Belt Drive

24 Pole Motor

(Lever)

Anti-Skate

(Rotary)

Belt Drive

4 Pole Motor

be

intermixed.)

be

intermixed.)

Cue

TAPE

UNIT FEATURES

SEE NOTES BELOW

PART NO.

NOTE F

169-506 01A

169-545

169-546

969 51

969 52

969-54

969-55

969-56 TAN

969-57

969 58

969-59

969 60 TAN 969-61 VOR Cassette

969-62

969-63

A-7021 TAN

A-8051

MFG.

CODE

AMI/ML

TAN

TAN 8 Track

TAN

AM

I

VOR

AMI

TAN

8-TRACK/

CASSETTE

8-Track

Cassette

8-Track

Cassette

8-Track

Cassette

8-Track

Cassette

CHANNELS

PLAY

2

2 2 ALC

2

2 2

2

2 2 Full

2 2

2

2 2 2

2 2

2 2 Full

2

2 2 Full

RECORD

2

- -

2

ALC/FULL

FEATURE

2

2 ALC

2

MOTOR

NOTE B

NOTE A

Full

ALC

Full

Full DC/E

Full

NOTE B

AUTO

STOP

NOTE C

DC/M Full

DC/M

DC/E

DC/M

DC/E

DC/E Tape

DC/E

DC/M

DC/E

DC/M

DC/E

Four

R

Four

R/FFA

Four R,

Four R/FF

Tape

P/R

Four B

P/R/FF

Four

R/FF

Tape

P/R

Tape

P/R

All

Tape

P/R

-

Tape

P/R

Tape

P/R

Tape

All

Four

R/FF

Tape

P/R

USE

NOTE D

C

c

C, M

M

MA

M

C

M

MA

M

MISC.

FEATURES

MISC.

FEATURES

NOTE E

A2, C1 ,

FF, I, M,

P1,

R

A2,

C3, I, R

A2,

C3, FF, I, P2, R

A3,

C3, FF, I, P2,

R, RL

A3,

C4, CR, E, F, I,

P2,

RL, TC

A3,

C3, FF, I, M,

P2,

R, R L

A3,

C3, FF, I, M,

P2,

RL, RP

A3,

C4, CR, E, F, I, M, P2, R L, TB, TC, TE

A3,

C3, E, F, I, M,

P2,

RL, T, TB, TC,

TE A1,

C1, D, E, I, M, P2, PRL, RL,

TB3,

TC, TE3

A3,

C3, CR, D, E, F, I, M, P2, RL, T, TB/TE, TC

A2,

C3 A3,

C3, E, F, I, M, P2,

RL, T, TB, TC, TE

A3,

C3, CR, D, E, F, I, M, P2, RL, TB/TE,

TC

A1 , C1, D, E, I, M, P2,

PRL, RL, TB3,

TC,

TE3 A2,

C3, FF, I, M, P2,

RL, PP A2,

C4, CR, E, F, I, M, P2, RL, TB, TC,

TE

NOTES

NOTE A - RECORD

ALC = Automatic Level Control Full = Full Feature with Record Level Controls and Meters.

NOTE B - MOTOR

E = Electronic Governor M = Mechanical Governor

AC Motors require conversion kit if used on 50Hz.

NOTE C - AUTO STOP

Full = Stops after each program, fourth program or runs continously (in

both Play and Record modes). Selected by three position slide control.

Four R = Stops after fourth program in Record only. Four R/FF = Stops after fourth program in Record and Fast Forward only. Four

R/FFA

programs in Fast Forward.

Four B Forward only if Auto Stop Button is depressed. Tape P/R = Tape tension sensor at end of tape in Play and Record only. Tape All = Stops at end of tape in Play/Record/Fast Forward/Rewind modes.

NOTE D - USED IN

C = Console M = Modular MA = Modular Accessory W = Wedge Modular

= Stops after fourth program in Record and after all

P/R/FF

= Stops after fourth program in Play, Record and Fast

NOTE E - MISC. FEATURES

=

Parallel Blade Power Connector.

A1

=

Molex Type Power Connector.

A2

= Hard Wire Power Connector.

A3 B = Bias Frequency Switch. C1 = RCA Type Audio Connector.

=

Spade Lub Audio Connector.

C2

Hard Wire Audio Connector.

=

C3

=

Molex Type Audio Connector.

C4

=

Cue/Review.

CR

Dolby Noise Reduction System. Dolby is a trademark of Dolby

D

=

Laboratories, I nc.

E

=

Eject. F = Interlocked Fast Forward Button. F

F

Fast Forward Button (Push-Push Type).

=

I

Interlocked Record Button.

=

M

Record Level Meter (Illuminated).

=

Pause Button (Push In, Slide Left to Lock).

P1

=

Pause Button (Push-Push).

P2

=

Peak Record Light.

PRL

Automatic 2/4 Channel Switching, with mode indicator.

Q

=

Ready Light or Auto Stop Light.

R RL = Record Light. RP = Repeat Button. T = Tape Run Light.

= Tape Bias Switch (C

TB TB3 = Tape Bias Switch (CrO2/FeCr/Fe3O2) TC = Tape Counter. TE = Tape Equalization Switch (Cr02/Normal).

Tape Equalization Switch (High, Mid, Low).

=

TE3

/Normal).

rO2

•

NOTE F - PART NUMBERS

169-

Base numbers identify units with electronics while 969- and Abase numbers identify units without electronics (mechanism only). Features listed in Notes "A", "C" and "E" for 969- and A- base numbers include features which may vary with model application.

7

INTRODUCTION

This service manual contains detailed service information for common among the three, all sections of Models

Illustrations of the three models covered in this service manual of the three models,

appear below. As will be noted from the illustrations, styling is

MC7031,

MC7041 and

MC7051.

On the following pages are Feature Charts and Specifications

8

PRODUCT FEATURES

X OR LETTER DENOTES FEATURE INCLUDED AND NUMBER DENOTES QUANTITY: D = ROTARY DETENT ACTION (CENTER

FEATURES

POWER OUTPUT

(Min. T.H.D. NO MORE THAN BANDWIDTH OF 20 Hz - INTO AN 8 OHM LOAD TUNER/AMPLIFIER CONTROLS

VOLUME

BALANCE

TREBLE

BASS D

TUNING

TUNER/AMPLIFIER SWITCHES

POWER

LOUDNESS

HI FILTER P

LO FILTER P

SPEAKER

MONO/STEREO P

FM MUTE P

FM AFC

FM DE-EMPHASIS (on back)

TAPE MONITOR P TAPE DUBBING BANDSWITCH - POSITIONS

DETENT ON BALANCE CONTROL), F = ROTARY FLYWHEEL, K = KEYBOARD TYPE, P = PUSH BUTTON TYPE,

MODEL NUMBER

PRODUCT TYPE

R = ROTARY TYPE, S = SLIDE TYPE, T = TOGGLE TYPE

MC7031

AM/FM AM/FM

MC7041

MC7051

AM/FM PRODUCT TYPE

FEATURES

MODEL NUMBER MC7031

AM/FM AM/FM

TUNER/AMPLIFIER CONNECTORS

R.M.S.

per Channel) 15W 25W

OFF,

A, B or A+B R

AM R

FM

PHONO

AUXILIARY INPUT

MICROPHONE

0.1%

20 kHz

D

F F

T P

P S

- -

4

R R R R

- -

0.08%

20 Hz -

20 kHz 20 kHz PHONO IN - MAGNETIC

D D D D D D HEADPHONE (STEREO) D D EXTERNAL ANTENNA

T T T AC OUTLETS - UNSWITCHED T T T

R R T T T T S S T T

4 6

R R FM/AM (ILLUMINATED)

R R

R

40W

0.05%

20 Hz - PHONO IN - CERAMIC

F FM -300OHM BALANCED

T

T PHONO GROUND TERMINAL

T

-

T

2R

R R

TAPE INPUT TAPE OUTPUT

AUXILIARY INPUT SPEAKER OUTPUT -

PUSH TYPE (Pair) 2 2

FM - 75 OHM UNBALANCED

SWITCHED

MICROPHONE INPUT

TUNER/AMPLIFIER FEATURES

FM STEREO INDICATOR LIGHT FUNCTION INDICATOR LIGHTS

TUNING METER (ILLUMINATED)

CENTER READING FM

SIGNAL STRENGTH METER

SPEAKER PROTECTION FUSES X X SPEAKER PROTECTION CIRCUIT

X X 2 X X 2 X X X X X

X X

X X X X X

AM X X X

X

- -

X

- -

X X X

-

MC7041

X

X X

-

MC7051 AM/FM

-

2

X

2

X

-

X

9

GENERAL INFORMATION

THEORY

From time to time Zenith includes the use of new components and circuit applications in product design. Theory and explanation of such components and circuits is included in various manuals. Refer to inside front cover for further information.

CIRCUIT BOARD COMPONENT IDENTIFICATION

In order to assist the Service Technician, most circuit boards are marked to identify the location of components, test points, etc.,

using the schematic reference symbols and numbers. We have also prepared a drawing of the foil side of the circuit board showing the relationship between the components and the

foil.

This will aid the Technician in quickly tracing circuits, as not only are the components shown, but also the voltages at various check points. Components are identified by a letter/ number combination. A letter prefix to indicate the type of component: C=Capacitor, L=Coil, R=Resistor, CR=Diode, etc. The numbers are assigned, in blocks, to identify the circuit in which it is used:

Block Stage Example

1 - 99 FM Tuner R1, C1, L1.

101-

199 AM Tuner R101, C101, L101. 201 - 299 IF R201, C201, L201. 301-

399 Multiplex R301, C301, L301. 401 - 449 Main Preamp, Right Channel R401, C401, L401.

451 - 499 Main Preamp, Left Channel R451, C451, L451.

501-

599 Power Supply R501, C501, L501.

901-

949 Phono Preamp, Right Channel R901, C901, L901.

951-

999 Phono Preamp, Left Channel R951, C951, L951. 1401 - 1449 Power Amp, Right Channel R1401,C1401, 1451 - 1499 Power Amp, Left Channel R1451,C1451,

L1401. L1451.

c. Remove the old IC and be certain that the holes in the

circuit board are free of solder.

d.

Apply a heat conductive grease to the metal heat sink

surface against which the metal plate of the IC will be placed.

This grease can be obtained in quantities by

ordering Part No. 205-303.

e. Insert IC pins into correct holes in the circuit board.

f. Insert a screw through each of the IC's mounting holes.

Tighten the screws until they are snug. CAUTION — Do not overtighten these screws as too much force may cause internal damage to the IC.

g.

Solder all leads, being certain that solder does not bridge

to other pins, causing shorts which may damage the IC or external components.

4. Do not operate these amplifiers without their proper speaker load.

5. Do not short out the audio output of either channel when the amplifier is operating.

FM AGC VOLTAGE CURVE

Voltage developed at the AGC terminal of the IF IC (pin 15) varies depending on the IF voltage sampled in the chip. If a fixed input signal level were applied to several samples of a given chassis model, the measured AGC voltage for that

input level will vary among the samples. Voltage measured

under these conditions is not a complete indicator of proper AGC action.

Two important points must be noted:

1. When servicing these products, the Service Technician must plotted for a curve). consider the following:

1.

One integrated circuit is used for both channels of the power creases to approximately 1000 microvolts.

output stages. • • • • • • •

2.

Should a power output stage

a. Check for shorts between the integrated circuit outputs

(pins 5 and 11) and other pins. b. Check voltages at the IC pins. c. Check for defective components external to the IC,

including in the power supply.

3. Replace the power output IC in the following manner. a. A replacement power output IC normally has a kink in

each pin. This is the point at which the pins are to be bent when required to fit the circuit board.

b. Bend the pins at right angles at the kink in each pin.

CAUTION — Do not flex leads as this may cause internal damage to the IC.

fail;

MINIMUM RATED POWER OUTPUT PER CHANNEL INTO 8 OHMS

MODELS

MC7031 MC7041 2 25 MC7051 2

(SINE WAVE CONTINUOUS AVERAGE POWER -

OFTEN CALLED RMS POWER)

NUMBER OF

CHANNELS

WATTS PER

CHANNEL

2 15

40

General shape of the voltage curve (when the voltages are

2.

AGC voltage will start to drop as the RF input level in-

POWER

BANDWIDTH

20 Hz-20 KHz 20 Hz-20 KHz 0.08% 20 Hz-20 KHz 0.05%

TOTAL HARMONIC

DISTORTION (THD)

NO MORE THAN

0.1%

10

AM/FM/MULTIPLEX ALIGNMENT

GENERAL

These receivers have been aligned at the factory and normally will not require further adjustment. As a result, it is not recommended that any attempt be made to alter the stages. If any components are replaced or if anyone tampers with the adjustments, realignment may be necessary.

AM ALIGNMENT

It is recommended that AM IF's be aligned by the sweep method shown in the alignment procedure on the following pages.

If your signal generator does not have sweep capabilities

for the AM IF, use the alternate alignment procedure shown.

FM ALIGNMENT

Because of the wide band pass required in a FM Multiplex

tuner, it is desirable to use an FM signal generator having a

deviation of 250kHz as well as an oscilloscope, when aligning

both the FM IF and RF portions of this receiver. It is not only

necessary to obtain maximum amplitude in the IF amplifier

stages,

but also necessary to maintain symmetry. It is desirable

to use markers in obtaining IF curve symmetry.

Capacitors mentioned in the alignment procedure should be as small in size as possible and the ground lead of the generator must be connected to ground as close as possible to the point of injection.

MULTIPLEX ALIGNMENT

Before any attempt is made to align, or service, FM Multiplex circuitry, the technician must be certain that the RF, IF, and Detector alignment is correct, and that the receiver functions normally on monaural signals.

Most Multiplex generators are excellent troubleshooting devices because they provide a composite Multiplex signal as well as an RF signal (which is FM modulated by the composite

multiplex signal). The composite signal is very useful since it can be used in signal tracing the Multiplex portion of the

receiver. We do not recommend that Multiplex alignment be made using the composite signal injected at the output terminal of the Detector since there is alway some phase shift occurring in the RF, IF or Detector circuits. As a result, Multiplex alignment made by a signal injected at the Detector input would not be correct. For proper Multiplex alignment, the composite signal must FM modulate the RF carrier and then be fed into the FM antenna terminals. With the signal injected in this manner, the Multiplex alignment would then be the best that could possibly be obtained.

RF signals should be injected at a point in the FM band where no signal is present. If at all possible, this should be at a frequency near the middle of the FM band. Tune the FM receiver to this point and adjust the RF frequency adjustment on the generator to this same frequency. The AGC voltage developed in the receiver should be maximum. The AGC voltage substantially less than this may indicate the RF frequency is tuned to an image.

GENERAL TROUBLE-SHOOTING PROCEDURE

Should a problem arise in aligning the FM Multiplex portion of the receiver, the technician must determine whether the difficulty lies in the RF, IF, and Detector portions of the receiver, or whether the difficulty lies in the Multiplex portion. The composite output of the multiplex generator can be injected at the output of the Detector to help determine the area of difficulty. To reduce possible extraneous signals coming through a Detector, short the Detector primary with a jumper lead. The wave forms and their magnitude may vary slightly from chassis to chassis, however, they are quite indicative of what will be seen when signal tracing the Multiplex circuitry.

If all the waveforms are similar in form and magnitude to those indicated, it can be assumed that the Multiplex portion of the receiver is functioning properly and the problem lies ahead of this in the FM receiver. If any of the waveforms are missing at a latter point but are apparent at a previous point, circuitry between the two test points should be checked.

SCOPE PATTERN "A "

PROBE "A" - RF INPUT

SCOPE PATTERN "B"

PROBE "B"- DE-EMPHASIS

11

PROBE "C"- DETECTOR PROBE

RF,

IF, MPX AND AUDIO ALIGNMENT PROCEDURE

FOR MODELS

MC7031,

MC7041

STEP

CONNECT

GENERATOR

TO

DUMMY

ANTENNA

CONNECT

VTVM/

SCOPE TO

INPUT

SIGNAL

FREQ.

SET DIAL

TO

ADJUST

PURPOSE

AUDIO OUTPUT IDLE CURRENT ADJUSTMENT

CAUTION:

Be Certain That The Output Stages Have Been Adjusted For Proper Idle Current Under No Signal Input Conditions Before Perform-

ing Other Adjustments Or Alignment.

1

2

VTVM

Across R 1422

Across R1472

No Signal

I nput

R1412

R1462

Adjust Controls For 4mV Across Corresponding Resistors. This Would Be Approximately 15mA.

AM ALIGNMENT - PREFERRED METHOD - WITH AM SWEEP GENERATOR

NOTE:

For AM IF Alignment Use AM Sweep Signal Generator Of 10 KHz Deviation, 60 Hz Modulation For Full Bandpass Display. Bandswitch

In AM. Also Connect Modulation Frequency To Scope Horizontal. (If AM Sweep Not Available, See Steps 17 Through 31.)

Short Test Point "L" (AM Gang Antenna Section) To Chassis Ground.

3

Generator

Test Point "K"

4

5

6

7 8

9

1

0

1

1 12 13

14 15

16

AM ALIGNMENT - ALTERNATE METHOD - IF AM SWEEP GENERATOR IS NOT AVAILABLE

NOTE:

17

18

19

20

21

22

23 24

25 26 27 28 29 30 31

FM ALIGNMENT

NOTE:

32

33

34

35

Test Point "K"

AM IF Input

Remove Short Between Test Point "|_" And Chassis Ground.

One Turn Loosely

Coupled To AM

Wavemagnet

Antenna

For AM IF Alignment Use A Signal With 400 Hertz Modulation. Bandswitch in AM.

Short Test Point "L" (AM Gang Antenna Section) To Chassis Ground.

Test Point "K"

AM IF Input

Remove Short Between Test Point "L" And Chassis Ground.

One Turn Loosely

Coupled To AM

Wavemagnet

Antenna

For FM IF Alignment Use A Signal Of 250 KHz Deviation, 50 Hertz Modulation For Full Bandpass Display. Bandswitch In FM. Mute OFF. AFC

OFF.

Preset R208, R211, R303 And R313 To Mid Rotation Before Connecting Generator. Connect Generator Cable Ground To Gang Frame.

Shunt C1D To Ground With A .001 MF Capacitor.

Test Point "D"

FM IF Input

At Q2 Base

Generator

Output

Probe "A"

None

Generator

Output

Probe "A"

None

Generator

Output

Probe "A"

Scope

Detector

Output

Across R1 23,

Term.#104

Scope

Detector

Output

Across R 1 23,

Term.

#104

Term.

#104

Term.

#104

Term.

#104

Term.

#104

VTVM

Detector

Output

Across R123,

Term.

#104

Term.

#104

Term.

#104

Term.

#104

Term.

#104

Term.

#104

Term.

#104

VTVM

Detector

Output

Across R123,

Term.

#104

Term.

#104

Term.

#104

Term.

#104

Term.

#104

Scope

Detector

Probe "C"

Probe "C" Test Point

Test Point

"G"

At IC201

Pin 1

+ 455 KHz

Tune Generator To Center Total Bandpass Waveform. Do Not Change Generator Frequency

For Remainder Of AM IF Alignment.

Center

Freq.

Center

Freq.

Center

Freq.

Of Ceramic

Filter In T102

Repeat Steps 6, 7 & 8 For Minimum Change.

1400 KHz

600 KHz 600 KHz T101

Repeat Steps 11 & 12 For Minimum Change.

1400 KHz

600 KHz 600 KHz

Repeat Steps 14 & 15 ForMinimum Change.

+ 455 KHz Gang

Rock Generator While Adjusting L104 (T102 Primary) For Maximum.

Rock Generator While Adjusting L105

(T102 Secondary) For Maximum.

Repeat Steps 19 & 20 For Minimum Change.

Equal Output Should Be Found If Generator

Is Detuned Equal Frequency Each Side

Maximum.

Center

Freq.

Center

Ceramic Filter

1400 KHz 1400 KHz

Repeat Steps 26 & 27 For Minimum Change.

1400 KHz 1400 KHz

Repeat Steps 29 & 30 For Minimum Change.

± 10.7 MHz

Tune Generator To Center Total Bandpass

Waveform. Do Not Change Generator Frequency

For Remainder Of FM IF Alignment.

Center

Of Ceramic Filters Y201, Y202,

Of

Freq.

Of

In T102

600 KHz

600 KHz 600 KHz

Freq.

Y203.

Gang

Closed

Gang

Closed

1400 KHz C1 K

1400 KHz

Closed

Gang

Closed

600 KHz T101

Gang

Closed

Gang

Closed

-

L104,

L105

(T102)

T103 T104

C1

G

L111 If Necessary

1 1 03

T104

C1

K

C1G

L111 If Necessary

-

T201

Adjust Generator To Center

Adjust Generator To Center Frequency Of Ceramic

Frequency Of Ceramic

Adjust For Maximum Gain And Symmetry.

Adjust For Maximum.

Set Oscillator To Dial Scale.

Align Antenna Stage.

-

Adjust For Maximum.

Set Oscillator To Dial Scale.

Align Antenna Stage.

Align I.F. Transformer For Maxi-

Align I.F. Transformer For Maximum Output And Symmetry As

mum Output And Symmetry As

mum Output And Symmetry As Indicated In Scope Pattern "A".

Indicated In Scope Pattern "A".

Filter.

12

RF,

IF, MPX AND AUDIO ALIGNMENT PROCEDURE

FOR MODELS

MC7031,

MC7041 - Cont'd.

STEP

36

37

NOTE:

38

CONNECT

GENERATOR

TO

Test Point "A"

FM Antenna Post

(Disconnect Antenna)

For FM Detector Alignment Use A Signal Of 75 KHz Deviation, 1 KHz Modulation. Also Connect Generator Modulation Frequency To

Scope Horizontal. Adjust Generator IF Frequency To Center Total Bandpass Waveform. Do Not Change Generator IF Frequency For Remainder Of IF Alignment. (If Your Generator Does Not Provide Output For Audio Modulation Frequency Use Horizontal Output From Generator, Or Scope Horizontal Sweep, And Follow Step 38C.) Minimum Distortion Can Only Be Achieved By Use Of Step 38A Below.

Test Point "D"

FM IF Input

At Q2 Base

DUMMY

ANTENNA

300 Ohm

Generator

Output

Probe "A"

CONNECT

VTVM/

SCOPE TO

A. Distortion

Analyzer

(Thru a 100

Usee Deemphasis Network

Probe "B"

And Scope.

B. Scope

C. Scope

INPUT

SIGNAL

FREQ.

+ 98 MHz

Center

Frequency

Of Ceramic

Filters Y201,

Y202,

Y203.

Y202,

Y203.

SET DIAL

TO

98 MHz

Gang

Closed

ADJUST

R211

(Mute)

R208

(Meter)

L205,

L206

(T202)

PURPOSE

Adjust For No Sound Output When Input Is Below With Mute Switch ON.

Adjust For A Reading Of 6 On Meter M102 With 60 dbV (1mV) Input.

A. Preferred Method: Distortion Analyzer At Test Point "H"

Should Read Minimum Distortion.

B. Alternate Method: Adjust For Linear Scope Trace - No Curve At Ends Of Trace. Disregard Meter Reading.

C. Alternate Method: Adjust For Maximum Length And Symmetry,

Similar To Scope Pattern "B".

1.7/xV

39

40 Test Point "A" 41

42 43 44

45 46 47

NOTE:

48

49

50

NOTE:

Test Point "A"

FM Antenna Post

(Disconnect Antenna)

Apply Sufficient Signal Level — Approx. 100 Microvolts — To Obtain Full Limiting At Point Near 98 MHz.

Do Not Readjust Control R303 After Step 48.

300 Ohm

Test Point

"H"

Frequency

Counter And/

or Scope

Test Point

"M"

Scope And/Or

AC VTVM

Left Tape

Output

Right Tape

Output.

106 MHz

90 MHz

Repeat Steps 40 & 41 For Minimum Change.

106 MHz 106 MHz C1C

90 MHz 90 MHz L2 If Necessary

106 MHz

90 MHz

Repeat Steps 43 Thru 46 For Minimum Change.

Unmodulated

R F Carrier

98 MHz

10%

Pilot

10%

Pilot

(L + R) (L - R)

(L Only)

106 MHz C1E Set Oscillator To Dial Scale.

90 MHz L4

106 MHz

90 MHz

L205

(T202)

C1

R303

(VCO)

R313

L1

A

Adjust For Center Reading On

Tuning Meter M101.

Set Oscillator To Dial Scale.

Align FM Detector Stage For

Maximum.

Align FM Antenna Stage For

Align FM Antenna Stage For Maximum.

Maximum.

A. Frequency Counter Should Read

19 KHz, +100 Hz.

B. Alternate Method: Connect Test Point "M" Signal To Scope Vertical And An Accurate 19 KHz Signal To Scope Horizontal Input. Adjust For One Square Synchronized Waveform.

Adjust For Separation. Maximum

Left Output.

Check For Separation. Minimum Right Output.

COLOR

CODE

Black

Blue

Red

Orange

White

CERAMIC FILTERS

NOMINAL CENTER

FREQUENCY

RANGE

10.64 MHz 10.61 to 10.67 MHz

10.67 MHz

10.70 MHz

10.73 MHz

10.76 MHz

10.64 to 10.70 MHz

10.67 to 10.73 MHz

10.70 to 10.76 MHz

10.73 to 10.79 MHz

13

RF,

IF AND MPX ALIGNMENT PROCEDURE

FOR MODEL MC7051

STEP

VOLTAGE REGULATOR ADJUSTMENT

CAUTION:

1

AUDIO OUTPUT IDLE CURRENT ADJUSTMENT

CAUTION : Output Stages Must Be Adjusted For Proper Idle Current Under No Signal

2

3

AM ALIGNMENT - PREFERRED METHOD - WITH AM SWEEP GENERATOR

NOTE:

4 Short C1J (AM Gang Antenna Section) To Chassis Ground. 5 Test Point "K"

6

7

8

9

10 One Turn Loosely

1

1 12 13

14 15

16

AM ALIGNMENT - ALTERNATE METHOD - IF AM SWEEP GENERATOR IS NOT AVAILABLE

NOTE:

17 Short C1J (AM Gang Antenna Section) To Chassis Ground.

18

19

20

21

22

23

24 Remove Short Between C1J And Chassis Ground. 25

26 27

28

29 30

31

CONNECT

GENERATOR

TO

Regulator Must Be Adjusted For Correct B+ Voltage.

- -

Conditions Before Performing Other Adjustments Or Alignment.

For AM IF Alignment Use AM Sweep Signal Generator Of 10 KHz Deviation, 60 Hz Modulation For Full Bandpass Display. Bandswitch

In AM. Also Connect Modulation Frequency To Scope Horizontal. (If AM Sweep Not Available, See Steps 17 Through 31.)

Test Point "K"

AM I F Input

Remove Short Between C1J And Chassis Ground.

One Turn Loosely

Coupled To AM

Wavemagnet

Antenna

For AM IF Alignment Use A Signal With 400 Hertz Modulation. Bandswitch In AM.

Test Point "K"

AM IF Input

One Turn Loosely

Coupled To AM

Wavemagnet

Antenna

DUMMY

ANTENNA

Generator

Output

Probe "A"

None Scope

None

Generator

Output

Probe "A"

None

CONNECT

VTVM/

SCOPE TO

VTVM

Pin 505

VTVM

Across R1418

Across

R1468

Scope

Detector

Output

Across R1 10

Detector

Output

Across R

Across R110

VTVM

Detector

Output

VTVM

Detector

Output

1 1

0

INPUT

SIGNAL

FREQ.

-

No Signal

Input

+ 455 KHz

Tune Generator To Center Total Bandpass Waveform. Do Not Change Generator Frequency For Remainder Of AM IF Alignment.

Center

Freq.

Center

Freq.

Of Ceramic

Filter In T102

1400KHz

600KHz

Repeat Steps 1 0 & 11 For Minimum Change.

0

1400KHz 1400KHz C1J

600KHz

Repeat Steps 13 & 14 For Minimum Change.

1000 KHz

+ 455 KHz

Rock Generator While Adjusting L103

(T102 Primary) For Maximum.

Rock Generator While Adjusting L104 (T102 Secondary) For Maximum.

Repeat Steps 19 & 20 For Minimum Change. Equal Output Should Be Found If Generator

Is Detuned Equal Frequency Each Side Maximum.

Center

Freq.

Of Ceramic

Filter In T102

1400 KHz 600 KHz

Repeat Steps 26 & 27 For Minimum Change.

1400 KHz

600 KHz

Repeat Steps 29 & 30 For Minimum Change.

1000 KHz

SET DIAL

TO

-

Gang

Closed

Gang

Closed

1400KHz

600KHz

1000 KHz

Gang

Closed

Gang

Closed

1400 KHz

600 KHz L102

1400 KHz

600 KHz

1000 KHz

ADJUST

R509

R1409

R1459

L103,

(T102)

T101

C1 K

L102

L101 If

Necessary

R106

T101

C1K

C1J

L101 If

Necessary

R106

-

L104

PURPOSE

Adjust For +33V.

Adjust Controls for 8 m V Across

Adjust Controls for 8 m V Across Corresponding Resistors. This

Corresponding Resistors. This Would Equal Approximately

Would Equal Approximately 16 mA.

16 mA.

Adjust Generator To Center

Adjust Generator To Center Frequency Of Ceramic

Frequency Of Ceramic

Adjust For Maximum Gain And Symmetry.

Adjust For Maximum.

Set Oscillator To Dial Scale.

Align Antenna Stage.

Adjust For A Reading Of 4 To 5 On Meter M102 With Input Of 74dBV(5mV).

—

Adjust For Maximum.

Set Oscillator To Dial Scale.

Align Antenna Stage.

Adjust For A Reading Of 4 To 5 On Meter M102 With Input Of 74dBV(5mV).

14

Filter.

RF,

IF AND MPX ALIGNMENT PROCEDURE

FOR MODEL MC7051 - Cont'd.

STEP

FM ALIGNMENT

Note: R21 1 And R303 To Mid Rotation Before Connecting Generator. Connect Generator Cable Ground To Gang Frame.

32

33

34

35

36

37

NOTE:

38

39

40 Test Point "A" 41 42

43 44 45

46 47 48 Audio Osc.

49

NOTE : Apply Sufficient Signal Level — Approx. 1 00 Microvolts — To Obtain Full Limiting At Point Near 98 MHz.

50

51

52

NOTE:

CONNECT

GENERATOR

TO

For FM IF Alignment Use A Signal Of 250 KHz Deviation, 50 Hertz Modulation For Full Bandpass Display. Bandswitch In FM. Preset R208,

Shunt C1B To Ground With A .001 MF Capacitor.

Test Point "D"

FM IF Input

At High Side

Of C1F

Test Point "A"

FM Antenna Post

(Disconnect Antenna)

For FM Detector Alignment Use A Signal Of 75 KHz Deviation, 1 KHz Modulation. Also Connect Generator Modulation Frequency To

Scope Horizontal. Adjust Generator IF Frequency To Center Total Bandpass Waveform. Do Not Change Generator IF Frequency For

Remainder Of IF Alignment. (If Your Generator Does Not Provide Output For Audio Modulation Frequency Use Horizontal Output From

Generator, Or Scope Horizontal Sweep, And Follow Step 38C). Minimum Distortion Can Only Be Achieved By Use Of Step 38A Below.

Test Point "D"

FM IF Input

At High Side

Of C1F

FM Antenna Post

(Disconnect Antenna)

Test Point "H"

Do Not Readjust Control R308 After Step 50.

DUMMY

ANTENNA

Generator

Output

Probe "A"

300 Ohm Scope

Generator

Output

Probe "A"

300 Ohm

—

CONNECT

VTVM/

SCOPE TO

Scope

Detector

Probe "C"

Test Point

At IC201

Pin 1.

Test Point

"H"

A. Distortion

Analyzer

(Thru A 100

Usee De-

emphasis

Network)

Probe "B"

And Scope.

B.Scope

C.Scope

Test Point

"H"

Test Point

"F"

Frequency

Counter And/

Or Scope

Test Point

"M"

Scope And/Or

AC VTVM

Left Tape

Output

Right Tape

Output.

INPUT

SIGNAL

FREQ.

10.7 MHz Gang

Tune Generator To Center Total Bandpass Waveform. Do Not Change Generator Frequency

For Remainder Of FM IF Alignment.

Center

Freq.

Of Ceramic

Filters Y201,

Y202,

Y203

98 MHz

Center

Frequency

Of Ceramic

Filters Y201,

Y202,

Y203.

Y202,

Y203.

106 MHz

90 MHz 90 MHz

Repeat Steps 40 & 41 For Minimum Change.

106 MHz

90 MHz 90 MHz

106 MHz 106 MHz

90 MHz

Repeat Steps 43 Thru 46 For Minimum Change.

200 KHz

Unmodulated

RF Carrier

98 MHz

1 0% Pilot

(L+R) (L-R)

(L Only)

SET DIAL

TO

Closed

Gang

Closed

98 MHz R216

98 MHz

Gang

Closed

1

06 MHz

1

06 MHz

90 MHz

ADJUST

R215

L204,

(T201)

C1D,

L3,

L2 If Necessary

T301 T302

R308

R318

T1

L205

C1H

L7

C1F L4

C1B

—

PURPOSE

Align I.F. Transformer For

Align I.F. Transformer For Maximum Output And Symmetry

Maximum Output And Symmetry

Maximum Output And Symmetry As Indicated In Scope Pattern "A".

As Indicated In Scope Pattern "A".

Adjust For No Sound Output

When Input Is Below

Mute Switch ON. Adjust For A Reading Of 4 To 5

One Meter M1 02 With Input Of 60dBV (1mV).

A. Preferred Method: Distortion Analyzer At Test Point "H"

Should Read Minimum Distortion.

B. Alternate Method: Adjust For

Linear Scope Trace-No Curve At Ends

Of Trace. Disregard Meter Reading. C. Alternate Method: Adjust For

Maximum Length And Symmetry,

Similar To Scope Pattern "A".

Adjust For Center Reading On

Tuning Meter M101.

Set Oscillator To Dial Scale.

Align FM Detector Stage For

Align FM Detector Stage For Maximum.

Maximum.

Align FM Antenna Stage For

Align FM Antenna Stage For Maximum.

Maximum.

Align For Minimum.

A. Frequency Counter Should Read 19 KHz, + 100 Hz.

B. Alternate Method: Connect Test Point "M" Signal To Scope Vertical And An Accurate 19 KHz Signal To Scope Horizontal Input. Adjust For One Square Synchronized

Waveform.

Adjust For Separation. Maximum Left Output.

Check For Separation. Minimum Right Output.

1.7/iV

With

CERAMIC FILTERS

COLOR

CODE

Black

NOMINAL CENTER

FREQUENCY

10.64 MHz 10.61 to 10.67 MHz

Blue 10.67 MHz

Red

10.70 MHz

Orange 10.73 MHz

White

10.76 MHz

FREQUENCY

RANGE

10.64 to 10.70 MHz

10.67 to 10.73 MHz

10.70 to 10.76 MHz

10.73 to 10.79 MHz

15

DISASSEMBLY PROCEDURES

FIGURE 1 - MODEL MC7041 - FRONT VIEW

CHASSIS ACCESS

Access to most areas of the chassis can be achieved by removal of the cabinet top and the bottom cover (See Figures 1 and 2). Numbers in parenthesis ( ) correspond to the numbers shown on exploded views and other illustrations.

2.

When removing bottom cover (2) note that the front edge

of bottom cover must be inserted under lip of front frame when it is reinstalled.

FRONT PANEL (ESCUTCHEON REMOVAL)

Certain components along the front edge of the chassis can be reached only after the front panel (3) has been removed:

CABINET TOP REMOVAL

1.

Remove two screws (83 on MC7031 and 82 on MC7041)

and their cup washers (58) located on each side of the cabinet (1).

2.

Lift cabinet (1) upward from chassis.

CHASSIS BOTTOM COVER REMOVAL

1.

Remove nine screws (82 on MC7031 and 81 on MC7041)

from bottom cover (2).

NOTE:

It is not necessary to remove the four screws

(81 on MC7031 and 80 on MC7041) holding the

four feet (59 on MC7031 and 87 on MC7041).

1.

Loosen the alien screw (recessed in tuning knob assembly)

holding tuning knob assembly (6) to tuning shaft (18 on MC7031 and 20 on MC7041).

2.

Remove tuning knob assembly from shaft.

3. Remove remaining knobs by pulling outward.

4. Remove five screws from the front panel (3).

a. Three screws (74 on MC7031 and 77 on MC7041)

are located on the bottom.

b. Two screws (72 on MC7031 and 86 on MC7041)

are located on the top.

5. Remove front panel (3) by pulling outwards.

FIGURE 2 - MODEL MC7041 - BACK VIEW

16

FIGURE 3 - MODEL MC7041 - CHASSIS VIEW

DIAL LIGHT REPLACEMENT

Four wedge base type lamps (DS501 through DS504) are

used in these models. They may be replaced in the following

manner.

1.

Remove cabinet top (1) as explained above.

2.

Lamps are mounted in grommets (60 on MC7031 and 21

on MC7041).

3. Remove grommet and lamp.

4. Lamp is soldered to leads within grommet.

5. Carefully pull lamp out of grommet.

6. Unsolder lamp leads and remove lamp.

7. Solder new lamp to leads.

8. Press lamp into grommet, being certain that it is fully seated.

9.

Press grommet firmly into light reflector (23 on MC7031

and 22 on MC7041), using a twisting motion until it is secure.

10.

Be certain that leads are dressed away from the dial cord.

FIGURE 4 - MODEL MC7051 - FRONT VIEW

17

Zenith MC7031, MC7041, MC7051 Service Manual

Specifications and Main Features

Frequently Asked Questions

User Manual