Zenith 28T925 User manual

PHOTO

FACT*

Folder

ZENITH

MODELS

28T925,

28T96O,

28T961,

28T962,

28T963

VERT.

CENT.

CHANNEL

SELECTOR

FINE

TUNING

VERT.HOLD

FOCUS

HORIZ.

CENT.

DIAL

LIGHT

5W,

HORiZ.

DRIVE

CONTRAST

CONTROL

VOL.CONT.

ON-OFF

SW,

BRIGHTNESS

HORIZ.

PHASE

HORIZ.

HOLD

VERT.LIN,

HEIGHT

WIDTH

ZENITHMODEL

28T960

.TRADE

NAMEZenith,Models

28T925,

28T960,

28T961,

28T962,

28T963.

Chassis

28F20,

28F20Z,

28F21,

28F22.

MANUFACTURER

ZenithRadio

Corp.,

6001

Dickens

Ave.,

Chicago,

Illinois

TYPE

SET

Television

Receiver

TUBESTwenty-eight

POWER

SUPPLY

117

Volts,

Cycle

TUNINGRANGEChannels

through

RATING

3.11

Amps

@ 117

Volts

AGO

Adjustment

AlignmentInstructions

BlockDiagram

Horizontal

Frequency

Adjustment

HorizontalPhaseAdjustment

Parts

List

and

Description

Photographs

Capacitor

Identification

Chassis-Top

View

INDEX

Photographs(continued)

6,7

14,15,16,17

5,8

PowerSupplyChassis

Tuner

Resistor

Identification

Trans.,

Inductor

and

Alignment

Identification

Schematic

Tube

PlacementChart

Voltage

and

ResistanceMeasurements

11,18

4,9

HOWARD

SAMS

CO.,INC.

Indianapolis

Indiana

"The

listing

ofany

available

replacement

part

herein

does

not

constitute

inany

case

recommendation,

warranty

guaranty

Howard

Sams

Co.,

Inc.,

tothe

quality

and

suitability

such

replacement

part.

The

numbers

these

parts

have

been

compiled

from

information

furnished

Howard

Sams

Co.,

Inc.,

bythe

manufacturers

ofthe

particular

type

replacement

part

listed."

"Reproduction

use,withoutexpresspermission,

editorial

pictorial

con-

tent,

inany

manner,

prohibited.

patent

liability

assumed

with

respect

the

useofthe

information

containedherein.

1949

Howard

Sams

Co.,

Inc.,

Indianapolis

Indiana,

S.of

America.

under

In-

ternational

Union.

All

rightsreservedunderInter-American

Union

(1910)

Howard

Sams

Co.,Inc."

Printed

inU.S.of

America

DATE

6/49

4912-15

SET#64

FOLDER

±1

B7~ra

ib.

rh;

PHOTOFACT

STANDARD

NOTATION

SCHEMATIC

Howard

Soms

Co.,

Inc.

1949

PAGE

THE

COOPERATION

OFTHE

MANUFACTURER

THIS

RECEIVER

MAKES

POSSIBLE

BRING

YOU

THIS

SERVICE

ANTENNA

ADJ.

CHASSIS

TOP

VIEW

C9618Z

'Z96L9Z

'196JL8S

'O9618S

S13QOW

H1IN3Z

CHASSIS

BOTTOM

VIEW-TRANS.,

INDUC

PAGE

JCTOR

AND

ALIGNMENT

IDENTIFICATION

PAGE

IVO-AOA

wonoa

SISSVHO

39Vd

CAPACITOR

IDENTIFICATION

PAGE

ALIGNMENTINSTRUCTIONS

VIDEO

ALIGNMENT

Connect

-1.5

volt

bias

battery

AGO

line.Remove

theAGO

tube

(V8)

and

connect

the

negative

side

ofthe

bias

battery

testjack

"0"andthe

.positive

side

chassis.

Connect

the

synchronizedsweep

voltage

from

the

signalgenerator

tothe

oscilloscope horizontalamplifierInput

for

horizontaldeflection.

Remove

the

oscillatortube

(V3)

during

the

video

alignment.

disable

the

high

voltageremove

the

horizontaloscillatortube

(V22)

from

its

socket.

DUMMY

ANTENNA

500MMF

Direct

SWEEP

GENERATOR

COUPLING

High

side

(Grid)

6AH6

(V6)

..ow

side

chassis

High

side

[Grid)

6AU6

(V5)

jOW

side

chassis

-Ilgh

side

topin1

(Grid)

6AU6

(V4)

Low

side

chassis

Ilgh

side

toan

ungroundedtube

shield

slippedover

the

convertertube.

Low

side

chassis

SWEEP

GENERATOR

FREQUENCY

24MC

(10MC

Sweep)

MARKER

GENERATOR

FREQUENCY

.-6MC

25.9MS

25.

SMC

22.2MC

25.

IMC

27.

SMC

21.

SMC

21.

SMC

22.

SMC

25.

IMC

25.

SMC

27.

SMC

CHANNEL

Any

CONNECT

SCOPE

Vert.

Amp.

thru

100KS2

test

Jack

"S"

Low

side

chassis.

ADJUST

Al,

A7,A8

A9,A10

REMARKS

Adjust

AlandA2to

obtainpattern

perFig1

withpeaksbeing

equalamplitude

andthe

21.6MC

marker

properlyplaced

onthe

pat-

tern.Adjust

A3to

place

25.9MC

marker

atthe

high

freq.

peak.

Check

position

21.

SMC

marker.

necessaryrepeatadjustment

Al,

A2andA3.

Reduce

sweepgeneratoroutput

until

amplitude

approximatelysame

thatobtained

step

Adjust

for

pattern

and

placement

25.

SMC

marker

asper

Fig

Adjust

for

pattern

and

placement

22.2MC

marker

asper

Fig

3.The

25.

IMC

shouldfallapproximately

shown

Fig

Use

maximummarker

amplitude

and

adjusttrap

ASso

27.

SMC

marker

disappears

"notch"

asper

Fig

Adjusttraps

A7and

for

minimum

indication

21.

SMC

marker

asper

Fig

Adjust

A9andA10

alternately

for

reasonably

flat

topped

pattern

per

Fig4.

Checkmarkers

tosee

that

theyaopear

proper

points

the

pattern.

The

SMC

marker

located

50%

onthe

high

freq.

slope

side

ofthe

overall

video

pattern

(Fig

SOUND

ALIGNMENT

The

sound

transformers

used

thisreceiver

have

specially

designed

slug's

and

require

special

alignment

tool.

(Zenith

Part

No.

68-7).

Bothslugs

eachtransformer

are

accessiblefrom

the

hole

inthetopofthe

trans-

former.

The

alignmentwrench

partiallyinserted

align

thetop

winding

and

fullyinserted

adjust

the

slug

forthe

bottom

winding.

DUMMY

ANTENNA

500MMF

500MHF

SWEEP

GENERATOR

COUPLING

Ugh

side

topin1

(Grid)

6AU6

(V13)

.,ow

side

chassis.

-ligh

side

topin1

(Grid)

6AU6

(Via;

Low

ide

chassis.

•liEh

side

topin1

(Grid)

6AUS

(Vli;

Low

side

chassis.

Ilgh

side

toan

ungrounded

tube

shield

placedover

the

mixertube

(V3).

Low

side

chassis

SWEEP

GENERATOR

FREQUENCY

24MC

(IMC

Sweep)

MARKER

GENERATOR

FREQUENCY

21.

SMC

CHANNEL

Any

•

CONNECT

SCOPE

Vert,

&mp.

Polnt^N

Low

side

chassis.

Vert.

Amp.

Point-op

Low

side

chassis

ADJUST

All,

A13,

A14

A15,

A16

A17

REMARKS

Adjust

AllandA12for

maximum

amplitude

and

symmetry

asper

Fig

with

21.

SMC

marker

center.

The

peak

peakdiscriminatorwidth

approximately

450KC.

Adjust

for

maximumamplitude

and

symmetry

asperFig6.

10.

FIG.

PAGE

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