Philco 48-1000 User manual

PHILCO

SERVICE

.SERVICE

Phiico

Television

Receiver,

Model

48-1000

MODEL48-1

000

SPECIFICATIONS

Description:

Ten-inch,

direct-view,table-model,

televisionreceiver.

FrequencyRange:

Television

broadcast

channels

1

through

13.

Number

of

Tubes:

Twenty-six.

Antenna:

Provisions

fortwo

antennas,

one

each

forthelowand

high

bands.

Transmission

Line:

300-ohm

balanced

type.

ChannelTuning:

Eight-position

Turret

-

Tuner,

with

snap-intypecoils

forthe

designated

channels

forthe

televisionbroadcast-

ing

area

in

which

the

receiver

isto

be

used.

Intermediate

Frequencies:

Video

carrier—26.6

megacycles.

Audio

carrier—22.1

megacycles.

Operating

Voltage:

110—120

volts,

60

cycles,

a.c.

Power

Consumption:

275

watts.

Power

Supplies:

325

volts

d.c.

at300

ma.,

7300

volts

d.c.

at200

microamperes(approx.).

Audio

Detector:

Ratio-type

FM

detector.

A.F.C.:

Automatic

tuningwithelectronic

control.

A.V.C.J

Automatic

levelcontrol

of

picture

and

sound.

Tone

Control:

Continuouslyvariable,treble

to

bass.

BassCompensation:

Tapon

volumecontrol.

Audio

Output:

2.5

watts.

Speaker:

Six-inch,

permanent-magnet,

namic,

3.2-ohm

voicecoil.

dy-

Picture

Presentation:

Ten-inch

directview,magnetic(par-

tially

permanentmagnet)

focus,

mag-

neticdeflection.

D-C

Restoration:

1N34

crystal

diode.

Deflection

Generation:

Hard-tube

oscillators.

2

COPYRIGHT,

1947,

PHILCO

CORPORATION

MODEL

48-1000

GENERAL

DESCRIPTION

PhilcoTelevisionReceiver,Model48-1000,

is

a

wide-bandsuperheterodynevideoreceiver

combinedwith

anFM

audioreceiver,incorporat-

ingthe

mostmoderncircuitdevices.Outstand-

ing

circuitadvancesinclude

the

PhilcoPrecision

ChannelSelector,whichgives

greater

selectivity

and

higher

gain

inthe

radio

frequency

circuits,

automatictuningwithelectroniccontrol,which

counteracts

any

frequency

drift

ofthe

incoming

signal,

and

automaticcontrol

of

picture

and

sound,whichovercomes

the

fading

of

high-fre-

quency

signals.Theseadvancements,combined

withprecisionconstruction,reduce

the

number

of

operatingcontrols

tofive,

thussimplifying

the

use

ofthe

receiver.

INSTALLATION

AND

OPERATION

CHOOSING

A

LOCATION

FORTHE

RECEIVER

In

selectinglocations

forthe

receiver

and

antenna,

the

owner

ofthe

televisionreceiver

will

decide

the

exactlocation

forthe

installation.

However,

the

television

serviceman

canbeof

assistance

tothe

owner

inthe

selection

ofa

good

location,

andcan

thereby

do

much

to

promote

ownersatisfaction.Certainfactorsshould

be

brought

tothe

owner'sattention

in

choosing

the

receiver

location.These

factors

include:

Room

Lighting

The

roomneed

notbe

dark

to

view

the

televisionprogram;

a

smallamount

of

general

lighting

is

evendesirable.

The

receivershould

be

so

located thatsunlight

or

light

fromlamps

will

not

falldirectlyupon

the

picturescreen,

or

cause

glare

or

reflections

inthe

eyes

ofthe

audi-

ence.

It is

advantageous

to be

ableeasily

to

darken

the

roomsomewhat

for

viewing

of

day-

time

programs.

The

picture

will

appearclearer

if

the

receiver

isnot

placednear

a

window,

so

thatdaylight

will

notbe

directly

in

back

of,or

on

eitherside

ofthe

picturescreen.

SeatingSpace

The

picture

canbe

viewedcomfortably,

by

mostpeople,

from

a

distance

of

between

fiveand

fifteen

feet.

For

thisreason,

it is

well

to

locate

the

receiver

so

that

an

area

of

about

five

feet

by

fifteen

feet

is

available,

or

easilyarranged,direct-

ly

in

front

ofthe

receiver.

In

this

way,

guests

may

be

accomodatedmostconveniently.

Power

Facilities

The

chosenlocationshouldprovide

easy

access

toan

electrical

outlet,

andif

convenient,

a

groundingpoint.

Interference

Sources

Although

thenew

Philco

television

circuits

arenot

easilydisturbed

by

outsideelectrical

disturbances,

itis

advisable,wherepossible,

to

locate

the

receiver

andthe

transmissionline

at

a

distancefromelevators,largeelectricmotors

and

similarsources

of

possibleinterference.

Alternate

Receiver

Location

If

it

appearsthatthere

aretwo

possible

locations

forthe

receiver,considerationshould

be

given

to

providingfacilities

in

case

the

owner

wishes

to

move

the

receiver

ata

later

date.

Usually,thisrequirement

canbemetby

making

the

transmissionline

long

enough

to

reach

the

alternatelocation

and

coiling

the

excessline

at

someconvenient

point

along

the

lead-inroute.

Figure

1

illustratessome

ofthe

items

tobe

con-

sidered

in

choosing

the

location

forthe

receiver.

WINDOW

/DOOR

CLEAR

AREA

FIGURE

1.

RECEIVER

LOCATION.

MODEL48-1000

TELEVISION

ANTENNAS

When

the

location

forthe

receiver

has

been

selected,

the

antennashould

be

installed.

The

antenna

isa

veryimportantpart

ofthe

installa-

tion

andthe

following

factors

enter

into

the

installation

problem.

Very-high-frequency

radiowaves,such

as

those

used

in

television,havesomecharacteristics

different

from

thoseused

in

ordinarybroadcast-

ing.

The

mostimportant

difference

isthe

straight-

line

travel

of

television waves,called

line-of-sight

propagation.

The

televisionbroadcastdoes

not

follow

the

curvature

ofthe

earth'ssurface

so

thatreliablereceptionbeyond

the

horizon

isnot

possible.

The

broadcast

canbe

intercepted

bya

hill

or

otherobstruction,thuspreventingrecep-

tion

bya

receiverlocatedbehindsuch

an

obstruc-

tion.

For

thisreason,

itis

necessary

to

locate

the

antenna

as

high

as

possibleabovesurround-

ing

objects.Anotherpeculiarity

of

television

waves

is

thatthey

reflect

from

solidobjects.

By

thisaction,

a

televisionsignal

can

reach

a

receiv-

ing

aerial

from

morethan

one

direction,

often

resulting

in

reception

ofthe

same

signal

from

the

same broadcastingstation

at

slightly

differ-

ent

times.This

effect

producesmultiplepictures,

or

ghosts,

onthe

televisionscreen.Reception

by

multiplesignalpathsmusttherefore

be

avoided.

Televisionreceptionrequires

theuseof

special

antennas.

The

mostcommontype

isthe

half-wave

dipole,consisting

oftwo

rods,each

DIPOLE

KIT

HIGH

FREQUENCY

45-1523

LOW

FREQUENCY

45-1525

AERIALFROM

KIT

45-1525

HOLES

SHOWN

IN

PAIRS

FOR

CHANNELNUMBERS

AS

SHOWN

1,2,

3.45,6

.ERIAL

FROM

KIT

45-1523

7

12

813

HOLES

FOR

CHANNEL

127

NUMBERS

AS

SHOWN

138

9

10

TP-2635

FIGURE

3.

DIPOLE

AND

REFLECTORAERIAL.

a

quarter-wavelong,separated

byan

insulating

member.

Seefigure2.

This

type

of

antenna

is

bi-directional

since

it

receivesequallywell

in

eitherdirection

at

right

angles

tothe

line

ofthe

rods,

but

receivesverypoorly

in

eitherdirection

in

linewith

the

rods.Such

an

antenna

canbe

usedwhere

itis

desired

to

receive

from

two

directions,

and

wherereflections,

or

ghosts

do

not

interferewithsuchreception.

Where

inter-

ference

occurs,

itis

necessary

tousea

moredirec-

tionalantenna,such

asa

dipole-with-reflector,

shown

infigure3.

Such

an

antennareceivesbest

only

from

the

directionindicated,

and

therefore

tends

to

suppressreflectionsarriving

atthean-

tenna

from

otherthan

the

direction

in

which

the

antenna

is

aimed.

Moreover,

the

dipole-with-

reflector

will

provide

a

strongerreceivedsignal.

The

length

ofthe

sections

ofthe

dipole

antenna

is

basedupon

free-space

wavelengths.

Thislength

canbe

convertedinto

the

physical

length

byuseofthe

following

formula:

Length

in

feet

of

each

Vi-wave

rod

234

Television

channel

frequency

in

megacycles

TP-2629

FIGURE

2.

SIMPLEDIPOLEAERIAL.

The

followingtableshows

the

length

ofthe

dipole(consisting

oftwo

quarter-waverods)

andthe

reflector

for

eachtelevisionchannel.

MODEL

48-1000

Channel

Number

1

2

3

4

5

6

7

8

9

10

11

12

Frequency

(me.)

44-50

54-60

60-66

66-72

76-82

82-88

174-180

180-186

186-192

192-198

198-204

204-210

Dipole

Length

(in

feet)

10.00

8.20

7.50

6.80

5.90

5.50

2.65

2.56

2.48

2.40

2.33

2.26

Reflector

Length

(in

feet)

10.50

8.60

7.85

7.15

6.20

5.80

2.78

2.69

2.60

2.52

2.44

2.37

FLAT

ROOF

SLOPING

ROOF

PEAKED

ROOF

BOTH

STAGGERED

SPLICE

OF

TRANSMISSION

LINE

FIGURE

5.

TP-2634

RECEIVER-AERIAL

CONNECTIONS.

TP-2631

FIGURE

4.

AERIAL-MASTINSTALLATION.

Antennas

canbe

constructedwhichoperate

with

fair

efficiency

overeither

thelowor

high

band

ofthe

televisionchannels,making

itun-

necessary

to

employ

"cut"

dipolesexcept

in

installationswheresignalstrength

is

abnormally

low,

or

where

interference

or

reflections

areex-

ceptionallytroublesome.

Transmissionlines

forusein

television

re-

ception

are

specifically

designed

to

match

the

antenna.

For

thisreason,

itis

necessary

to

employ

the

type

of

line

specified

forthe

receiver.

For

all

1948

ModelPhilcoTelevisionReceivers,

300-

ohm

parallel-wireline,Part

No.

45-1514,

is re-

quired.Installation

of

thislineshould

be

care-

fully

made,withspecialregard

to

properly

secur-

ingthe

line

at

intervals

ofnot

morethanthree

feet,

to

preventvibration

or

othertypes

of

damage

tothe

line.Connections

tothe

receiver

are

made

by

means

ofa

four-prong

plug

and

jack.

See

figure5.

Televisionantennainstallationsmust

be

madewithspecialemphasisupon

the

following

points.

1.

The

antennamust

be

placed

ina

high

position,clear

ofall

obstructions,

andin

line-of-

sight

ofthe

transmittingstation.

2.

The

antennamust

be

properlyaimed

to

obtainmaximumsignalstrength

and

freedom

from

echoes

and

interference.

3.In

areas

oflow

signalstrength,

itmaybe

necessary

tousean

antenna

of

specific

length

to

obtainbestresults.

MODEL

48-1

000

4.

Installation

oftwo

antennas,

oneforthe

low-frequency

band

andoneforthe

high-fre-

quencyband,

maybe

necessarywhere

signal

strength

or

interferenceconditions

are

unfavor-

able.

The

followingPhilcoantennas,

specifically

designed

foruse

withtelevisionreceivers,

are

available

inkit

form.

The

PhilcoLow-FrequencyAerialKit,Part

No.

45-1525

consists

ofa

dipoledesigned

for

channel

No.3,75

feet

of

300-ohm

transmission

line,

and

window-sillmountinghardware.

The

Philco

High-Frequency

AerialKit,Part

No.

45-1523consists

ofa

dipole

designed

for

channel

No.9,75

feet

of

300-ohmtransmission

line

and

window-sill

mounting

hardware.

The

PhilcoAerialMastKit,Part

No.

45-1465

contains

the

necessaryhardware

to

providemast-

mounting

for

televisionantennas.

The

PhilcoAll-WaveAerialKit,Part

No.

45-1522

contains

a

specialbroad-banddipole

array,

75

feet

of

300-ohm transmissionline

and

hardware

for

mast-mountingwhenusedwith

the

Mast

Kit.

The

All-Wave

Antenna

isnot

designed

for

use

with

a

reflector.

The

PhilcoLow-FrequencyReflectorKit,

Part

No.

45-1526

contains

a

reflector

dipole

de-

signed

for

channel

No.2,

adjustablespacer-

supportbar,

and

otherhardware

for

mast-mount-

ing

whenusedwith

the

Low-FrequencyAerial

Kitandthe

AerialMastKit.

The

Philco

High-FrequencyReflectorKit,

Part

No.

45-1524

contains

a

reflector

dipole

de-

signed

for

channel

No.8,

adjustablespacer-

supportbar,

and

otherhardware

for

mast-mount-

ing

whenusedwith

the

High-FrequencyAerial

Kitandthe

AerialMastKit.

Dipole

and

reflectorlengths

as

supplied

in

the

kits

are

chosen

to

provide

a

maximum

of

flexibilityin

reception

of

different

channels,with

a

minimum

of

cutting.Furtherinformation

and

installationdata

for

theseantennas

are

supplied

witheachkit.

PREPARING

THE

RECEIVER

FORUSE

Wheneverpossible,

the

receivershould

be

unpacked

and

prepared

foruseinthe

dealer's

shop,

so

that

operation

maybe

checked

under

knownconditions

of

antenna,interference,power,

and

similarfactors.

The

receiver

is

shippedwith

all

tubes

in

place,except

the

picture-tubeassembly.Unpack

the

receivercarefully,

and

inspect

the

chassis

and

cabinet

tobe

surethat

no

damage

has

been

in-

curred

in

shipment.Remove

the

protectivecover

from

back

ofthe

receiver

and

check

for

loose

tubes,

and

damagedparts.Unpack

the

picture

tube

and

inspect

for

damage.

To

install

the

pic-

ture

tube,

first

remove

the

receiverchassis

from

the

cabinet.Carefullyinstall

the

picture-tube

assembly

inthe

cabinet

as

shown

infigure6,and

tighten

the

threeboltssecurely.

TP-2946

FIGURE

6.

PICTURE-TUBEASSEMBLY

INSTALLATION.

Insert

the

coils

inthe

PhilcoPrecisionChan-

nel

Selector,

as

shown

infigure7.

Note

the

posi-

tion

ofthe

selector

and

insert

the

coils

in

numer-

ical

channelsequence,correspondingwith

the

eightpositions

ofthe

channelselectorswitch.

Replace

the

chassis

inthe

cabinet,

andse-

curely

tighten

the

mountingbolts.Connect

the

deflection-assembly

plug,

the

picture-tubeplug,

andthe

high-voltagecable.

Insert

a

test

lead

intheAFC

testjack(J200)

inthe

frontcorner

ofthe

chassis

for

connection

MODEL

48-1000

FIGURE

7.

TP-2756

TUNER-TURRET

COIL

INSERTION.

to

a

20,000-ohms-per-volt

voltmeter

and

replace

the

coverover

the

rear

ofthe

cabinet.Thistest

lead

will

be

used

for

adjusting

the

oscillatorcoil.

Plug

the

antennatransmission

line

into

the

antenna

jack

onthe

rear

ofthe

chassis

and

con-

nect

the

receiver

toa

source

of

115-volt,

60-cycle

alternatingcurrent.

CONTROLS

AND

ADJUSTMENTS

Fivecontrolknobs,locateddirectlybelow

the

viewingscreen

ofthe

receiver,provide

all

the

controls

for

normaloperation

ofthe

receiver.

These

five

controls

arethe

onlyones which

will

be

operated

bythe

user

after

the

receiver

has

beenplaced

in

service.

All

otheradjustments

must

be

made

bya

qualifiedtelevisionserviceman.

Thefive

operatingcontrolsshown

infigure8 and

identified

onthe

schematicdiagram,are,

from

left

to

right:

1.

CHANNELSELECTOR.

This

knob

ro-

tates

the

Philco

PrecisionChannelSelector,con-

necting

the

correctcoils

into

the

circuits

ofthe

selector,

and

connecting

the

correct

antenna

for

the

selectedchannel.

Turn

thisknob

tothe

chan-

nelofa

stationwhich

is

broadcasting.

2.

OFF-ON-TONE

CONTROL.

This

knob

controls

SlOO

and

R214,turning

onthesetinthe

first

position

of

clockwiserotation,

and

adjusting

the

bass

and

treble

response

inthe

remainder

of

the

rotation.

Turn

thisknobuntil

thesetis

switched

on.

3.

VOLUME

CONTROL.

This

knoboper-

atesR213,adjusting

the

amplification

ofthe

audio

signal.

Ithasno

effect

upon

the

videosignal.

Adjust

for

desired

volume.

4.

BACKGROUND

CONTROL.

This

knob

operatesR433,regulating

the

average

d-c

bias

of

the

picturetube,

and

affects

only

the

videooutput.

Turn

thiscontrolclockwiseuntil

the

picture-tube

screen

is

faintlyilluminated.

5.

CONTRAST

CONTROL.

Thisknob

ad-

justs

R431,controlling

the

amplification

ofthe

videosignal,thuscontrolling

the

extent

of

gray

range

inthe

picture.

Turn

thiscontrolclockwise

until

a

satisfactory

picture

is

obtained.

In

addition

tothe

operatingcontrols,

the

serviceman

will

use

twelveknurledknobs,

or

screwdriver-operated

controls

for

adjusting

the

various

circuitswhich

affect

the

overallperform-

ance

ofthe

receiver.

Sixof

thesecontrols

are

located

onthe

front

ofthe

receiverbehind

the

droppanel

as

shown

infigure8.

Fourcontrols

are

located

onthe

rear

ofthe

receiverchassis.

One

control

is

locatednext

tothe

channelselector

onthe

front

ofthe

receiver,

andone

control

is

located

ontopofthe

chassis.

The

drop-panel

controls

have

the

following

functions:

FOCUS

VERT.

HOR.

HEIGHT

HOLD

L<».

^".'

FIGURE

8.

DROP-PANEL

ADJUSTMENTS.

TP-2V45

MODEL

48-1000

6.

FOCUS

—

adjusts

R546,controlling

the

amount

of

current

flowinginthe

focusing

coil,

L502.

Adjustthiscontrol

to

obtainsharp

fine

sweep

lines

inthe

picture.

7.

VERTICAL

HOLD—adjusts

R517,

regu-

lating

the

free-running

frequency

ofthe

vertical-

sweep

generator.Adjustthis control

to

stop

any

vertical

shifting

ofthe

picture.

8.

HORIZONTAL

HOLD

—

adjustsR532,

regulating

the

free-running

frequency

ofthe

horizontal-sweep

generator.

Adjustthis

control

to

stop

any

horizontalmovement

ofthe

picture.

9.

HEIGHT—adjusts

R513,

controlling

the

amount

of

amplification

ofthe

verticalsweep,

and

thereforegoverning

the

verticaldimension

of

the

picture

onthe

screen.Adjust

the

control

until

the

picture

is

largeenoughvertically

to

just

fillthe

picture frame.

10.

VERTICAL

LINEARITY—adjusts

R522,

controlling

the

linearity

ofthe

verticalsweep

by

changing

the

operatingcharacteristics

ofthe

ver-

tical-sweep

outputtube.Adjustthiscontrol

to

obtain

a

symmetricaltestpattern

inthe

vertical

plane.

11.

HORIZONTALLINEARITY

—

adjusts

R540,

controlling

the

action

ofthe

horizontal-

sweepcontroltube whichgoverns

the

linearity

of

the

horizontalsweep.Adjustthiscontrol

to

obtain

a

symmetricaltestpattern

inthe

horizontal

plane.

HOR.

CENT.

VERT

CENT.

WIDTH

BEAM

BENDER

TP-2948

FIGURE

9.

ADJUSTMENTS

ON

REAR

OF

RECEIVER

CHASSIS.

The

controls

onthe

rear

ofthe

chassis

as

shown

infigure9,

are:

12.

BEAMBENDER

—

adjusts

R525,con-

trolling

the

amount

of

current

flowinginthe

beam-bender

coilL501.Adjustthiscontrol

to

obtain

the

brightest

possible

picture,

lowering

the

backgroundcontrol

as

necessary

to

determine

the

properposition

ofthe

beam-bendercontrol.

Nextmove

the

beam-bendercoilforward

and

backwardvery

slightly

onthe

picture-tubeneck

and

rotateslightlyuntil

the

brightestpossible

pictureshowsthat

the

coil

is

properlylocated.

13.

WIDTH

—

adjusts

L503A

and

L503B,

regulating

the

amount

of

deflectioncurrent

flow-

inginthe

horizontal-deflectioncoils,therebycon-

trolling

the

horizontaldimension

ofthe

picture.

Adjust

this

control

to

obtain

a

picture

wide

enough

to

just

fillthe

picture

frame.

14.

VERTICAL

CENTERING

—

adjusts

R524,

controlling

the

amount

and

polarity

ofthe

d-c

centeringcurrent

flowinginthe

vertical

de-

flection

coils.Adjustingthiscontrol

will

move

the

entirepicture

upor

down.

15.

HORIZONTAL

CENTERING—adjusts

R544,

controlling

the

amount

and

polarity

ofthe

d-c

centeringcurrent

flowinginthe

horizontal-

deflection

coils.Adjustingthiscontrolwillmove

the

entire

picture

tothe

left

or

right.

16.

A-V-C

AMPLIFIER—this

control

ison

thetopofthe

chassis

and

adjustsR423,regulating

the

amount

of

amplificationapplied

tothe

a-v-c

signal.

This

control

has

beenadjusted

atthe

fac-

tory

and

should

notbe

readjustedunlesscircuit

componentshavebeenaltered.Instructions

for

adjustment

are

includedwith

the

alignmentpro-

cedure.

17.

LOCAL

-

OSCILLATOR

-

COILTRIM-

MER—

This

control

is

located

onthe

front

of

the

chassis

andis

accessible

through

the

front

panel

after

removing

the

channelselectorknob

and

dial.

This

control

adjusts

the

core

ofthe

particularoscillatorcoil

inuseforthe

channel

beingreceived.

With

a

televisionsoundsignal

being

received,

adjustthis

control

to

obtain

a

reading

of0 onthe

20,000-ohms-per-volt

volt-

meter,previouslyconnected

totheAFC

testjack.

Thissettingshouldalsoresult

inthe

clearest

and

loudestsoundsignal.Makethisadjustment

for

eachchannel.

Operation

ofthe

receiver

should

be

checkedagainstanotherreceiver

if

there

isany

indication

of

incorrectoperation.

The

receiver

isnow

ready

tobe

installed

inthe

home.

Extreme

careshould

be

exercised

in

transporting

the

receiverfrom

the

shop

tothe

home,

so

that

the

receiverwill

notbe

damaged,

andso

that

final

adjustments

inthe

home

canbe

minimized.

Leave

theAFC

testleadconnected

inthe

receiver

until

the

homeinstallation

is

completed.

MODEL

48-1000

INSTALLING

THE

RECEIVER

Place

the

receiver

inthe

preparedlocation

and

connect

ittothe

antenna

and

powersource.

Turn

onthe

receiver

and

make

any

necessary

readjustments

ofthe

controls.

The

aiming

ofthe

antennashould

nowbe

checked.

With

the

receiveroperating,

the

antenna

should

be

rotated

byan

assistant,

while

the

service-

man

carefully

observes

the

appearance

ofthe

picture,

andthe

voltagedeveloped

attheAVC

test

jack

(J401).

Useofan

intercommunicating

system

betwen

the

serviceman

andhis

assistant

is

recommended,

andto

avoiderroneousresults,

the

assistantshouldmoveawayfrom

the

aerial

duringeachpositioncheck.

The

antennashould

be

placed

inthe

positionwhichgives

the

best

compromisebetweenmaximumsignal strength

(highestvoltage

attheAVC

test

jack)

andab-

sence

of

echoes

or

interferencepatterns.

In

cases

wherereception

is

desired

from

twoor

more

stations

inthe

samefrequencyband

but

which

are

located

in

different

directionsfrom

the

re

ceiver,

a

compromise

maybe

necessary,aiming

the

antenna

forthe

bestaveragesignal.

If

separ-

atelowand

high-bandantennas

are

used,each

antenna

must

be

aimedseparately.

Seefigure10.

CB3

/£.

\O

TP-2635

FIGURE

10.

AIMING

THE

AERIAL.

The

local-oscillator-coiltrimmershould

now

be

readjusted

for

eachchannelinstalled

inthe

receiver,

andany

other

controls

readjusted

to

t^t

obtain

the

bestpossibleperformance.(Thehold

controlsshould

be

readjusted

onthe

weakest

station

tobe

received.)

The

receiver

isnow

ready

for

usebythe

owner,

andthe

serviceman

should

explain

and

demonstrate

the

operation

ofthefive

operatingcontrols,using

the

owners'

"Users

Instructions",which

is

packedwith

the

receiver.

The

ownershould

be

cautionedagainsttamper-

ing

with

the

othercontrols,

and

againstremoving

the

coverfrom

the

back

ofthe

cabinet.Invite

questionsfrom

the

owner

andbe

sure

that

the

operating

instructions

are

understood

by

those

who

will

operate

the

receiver.

The

followingillustrationsshow

the

results

of

the

morecommonincorrectadjustments

of

controls

andmay

make

it

easier

forthe

customer

to

operate

the

receiver.

TP-3065

FIGURE

11.

BACKGROUND

TOO

HIGH.

TP-IV69

FIGURE

12.

HORIZONTALHOLD

IMPROPERLY

ADJUSTED.

MODEL

48-1000

TP-1974

FIGURE

13.

VERTICAL

HOLD

IMPROPERLYADJUSTED.

TP-1963

FIGURE

14.

FOCUS

CONTROL

IMPROPERLYADJUSTED.

CIRCUIT

DESCRIPTION

The

Model

48-1000

receiverschematic

is

dividedinto

five

majorsections

for

easycircuit

analysis.

Thesesections

arethe

Radio-Frequency

Section,

the

VideoSection,

the

AudioSection,

the

SweepSection,

andthe

Power-SuppliesSec-

tion.

This

division

is

clearlyshown

inthe

block

diagram,

figure 16,

whichalsoindicates

the

inter-

relation

ofthe

sections.

A

completeschematic

diagram

forthe

receiver

is

shown

infigure27.

RADIO-FREQUENCY

SECTION

To

providemaximumsensitivity

and

selec-

tivity,

consistentwith

a

six-megacyclepassband

inther-f

section,

a

separate

setof

coils

is

used

for

each

ofthe

thirteentelevisionchannels.

The

antennacoil

andther-f

amplifiercoil

for

each

channel

are

built

asan

assembly,

asarethe

mixer

coil

and the

local-oscillatorcoil,

so

that

two as-

semblies

comprise

a setof

coils

foranyone

televisionbroadcastchannel.

Any

eight

of

these

thirteensets

of

coils

maybe

easily

installed

in

the

PhilcoPrecisionChannelSelector,without

soldering

or

wiring.Since

a

maximum

of

only

seventelevisionbroadcastingstations

is

alloted

to

any

one

area,

the

PhilcoPrecisionChannelSelec-

toris

adaptable

foruseinany

portion

ofthe

country.

Provision

is

made

for

separatehigh-band

and

low-bandantennas

forusein

localitieswhere

signalstrength

or

otherconsiderationsmakesuch

an

arrangementnecessary.

When

correctantenna,antennacoil,

r-f

coil,

local-oscillatorcoil

and

mixercoilhavebeen

connected

into

the

circuit

by

setting

the

channel

selectorknob,

the

signal

from

the

antenna

is

transferred

tother-f

amplifiercircuit.

Here

the

signal

is

amplified

and

resistancecoupled

into

the

mixercircuit,where

it

heterodyneswith

the

output

from

the

local

oscillator

.to

produce

the

desiredvideo

and

audiointermediatefrequencies.

The

localoscillatorcomponents

are

especially

TP-2665-G

FIGURE

15.

RADIO-FREQUENCY

SECTION,

SCHEMATIC

DIAGRAM.

10

HIGH'

BANDA.RC

O

c

71

m

O

>

O

79

>

s

V

/LOW

\

BAND

PHILCO

AUTOMATIC

1ST

AUDIO

2ND

AUDIO

DISCRIM

I.F.

AMP.

I.F.

AMP.INATOR

x

nw

i

wwtni

i^

/

MICRO-TUNER

AUDIOSECTION

PHILCO

MULTI-

CHANNELTURRET-

TUNER

VIDEO

DETECTOR

s

6AL5

1ST

VIDEO

If.

AMP.

2ND

VIDEO

I.F

AMR

A.V.C.1

DETECTOR

6AG5

ADJ.

AUDIO

TRAPSIGNAL

7B6

(STABILIZER

A.V.C.

AMP.

MIXER

R.F.

SECTION

VIDEO

SECTION

VERTICAL

OUTPUTTRANS

SWEEP

SECTION

HOR.

SWEEP

GEN-

POWER

SUPPLY

SECTION

BEAMBENDER

COILS

FOCUS

COILS

DEFLECTION

YOKE

2

O

o

oo

-115V

60

CYCLE

SUPPLY

MODEL

48-1000

designed

and

constructed

to

obtain

the

highest

possibledegree

of

stability

andthe

output

ofthe

oscillator

is

inductivelycoupled

tothe

gridcir-

cuit

ofthe

mixer.

In

addition,

to

compensate

for

any

frequency

drift

ofthe

incomingsignal

as

well

asany

small

frequency

driftthat

may

arise

within

the

receiver,electronicautomaticfre-

quency

control

(called

automatic

tuning

with

electronic

control)

is

incorporatedwith

the

oscil-

latorcircuit.

A

controlsignalfrom

the

frequency

discriminator

inthe

audiosectiongoverns

the

action

ofthe

oscillator-controltube,raising

or

lowering

the

frequency

ofthe

localoscillator

as

necessary

to

maintain

atall

times

the

desiredinter-

mediate

frequency.

The

frequenciesexisting

in

the

variouscircuits

ofthe

receiverwhen

there-

ceiver

is

tuned

tothe

different

channels

are

shown

inthe

followingchart.

Channel

No.

1

2

3

4

5

6

7

8

9

10

11

12

13

Band

Width

(me)

44-50

54-60

60-66

66-72

76-82

82-88

174-180

180-186

186-192

192-198

198-204

204-210

210-216

Video-Carrier

Frequency

(me)

45.25

55.25

61.25

67.25

77.25

83.25

175.25

181.25

187.25

193.25

199-25

205.25

211.25

Audio-

Carrier

Frequency

(me)

49.75

59-75

65.75

71.75

81.75

87.75

179.75

185.75

191.75

197.75

203.75

209.75

215.75

Local-Osc.

Frequency

(me)

71.85

81.85

87.85

93.85

103.85

109.85

201.85

207.85

213.85

219-85

225.85

231.85

237.85

Video

I.F.

(me)

26.6

Audio

I.F.

(me)

22.1

Adj.

Audio

I.F.

(me)

none

32.1

28.1*

32.1

28.1*

none

28.1*

*Adjacent

audio

i-f

signalwithin

the

receiverpass

band.

(Rejected

bythe

adjacent-audio

trap,

as

explainedbelow).

THE

VIDEO

SECTION

The

intermediate-frequency

signals

from

the

mixer

stage

are

amplified

inthefirst

stage

ofthe

videosection.Thisstage

is

called

the

input

i-f

amplifier

because

it

amplifiesboth

the

video

i-f

signals

andthe

audio

i-f

signals.

The

audio

i-f

trap

inthe

input

ofthe1st

video

i-f

amplifier

stage

rejects

the

audio

i-f

signal,passingonly

the

compositevideo

i-f

signal (and

the

adjacent-

audio

i-f

signal,

if

present)

tothe1st

video

i-f

amplifier.

The

trap

inthe

input

tothe

second

video

i-f

amplifier

removes

the

adjacent

audio

i-f

signal,

allowingonly

the

compositevideo

i-f

sig-

naltobe

furtheramplified

and

passed

ontothe

videodetector

and

a-v-c rectifier.

Inthe

video

detector,

the

negativeportion

of the

video

i-f

signal

is

rectified

andthe

resultantnegativevideo

signal

is

amplified

inthe

video

amplifier

and

videooutputstages

and

applied

tothe

control

grid

ofthe

picture tube.

The

passband

ofthe

12

MODEL

48-100

videosection

is

approximately

4.1

megacycles

wide.

D-C

reinsertion,

or

restoration

is

accom-

plished

by

rectifying

a

portion

ofthe

videosignal

with

a

1N34

crystaldiode

and

applying

there-

sultant

d.c.

as

bias

tothe

picturetube.

The

positiveportion

ofthe

video

i-f

signal

at

the

detector

is

rectified

and

used

to

provide

a

bias

forthe

a-v-c

amplifier

stage.

A

high-fre-

quency

signal

is

applied

to

thistube

from

the

horizontal-sweep

generator.

The

amplification

of

thissignal

bythe

a-v-camplifier

is

controlled

by

the

bias

from

the

a-v-c

rectifier.

The

output

of

the

a-v-c

amplifier

tube

is

rectified

inthe

diode

section

ofthe

tube

andis

applied

asa

negative

a-v-c

voltage

to

control

the

amplification

ofthe

r-f

amplifier,input

i-f

amplifier,

andthefirst

video

i-f

amplifier.

The

amplifiedcontrol

ofthe

gain

of

thesethreestagesacts

to

nullify

the

effect

of

any

change

in

strength

ofthe

incomingsignal,

practically

eliminating

from

the

output

any

fad-

ing

that

may

occur

inthe

incoming

signal.

For

thisreasonthiscircuit

is

called

the

automatic

levelcontrol

of

picture

and

sound.

THE

AUDIO

SECTION

The

audiosection

isan

improved

FM

receiver,

consisting

oftwo

stages

of

audio

i-f

amplification,

a

discriminator,

one

stage

of

audio

amplification,

andan

audiooutputstagedriving

a

six-inchpermanent-magnetspeaker.

FIGURE

17.

VIDEOSEC-

TION.

SCHEMATIC

DIA-

GRAM.

TP-2665-H

Incorporated

intheFM

discriminatorcircuit

isa filter

circuitconnected

tothe

centerpoint

of

the

discriminatoroutput.

As

long

asthe

fre-

quency-modulated

i-f

signal

is

centeredabout

the

correct

frequency,

thed-c

outputvoltage

will

be

zero.

Ifthe

centerfrequencydriftsabove

or

below

the

correctvalue,

the

outputvoltage

will

be

a

positive

or

negative

d-c

potentialrespectively.

Itis

thispotentialwhich

is

used

to

control

the

action

ofthe

automatic

tuning

with

electronic

control,causing

the

intermediate

frequency

to

return

tothe

correctvalue.

THE

SWEEP

SECTION

The

synchronizingsignalscontained

inthe

compositevideo

signal

are

coupledfrom

the

screen

grid

ofthe

video amplifier

tothe

sync

separator.

The

syncseparator

plate,

screen

and

gridvoltages

are

chosen

so

that

the

video portion

of

the

signal

is not

amplified

in

thisstage,

and

the

outputcontainsonly

the

synchronizing

sig-

nals.

This

output

is

divided,being

fedto

both

the

horizontal

and

vertical-syncamplifiers.

In

each

of

theseamplifiers,

the

timeconstants

ofthe

FIGURE

18.

AUDIOSECTION,SCHEMATICDIAGRAM.

TP-2665-l

13

MODEL

48-1000

FIGURE

19.

SWEEPSECTION,SCHEMATIC

DIAGRAM.

TP-2665-J

circuits

havebeenchosen

to

accept

the

correcr

sync

pulses

and

reject

the

others(vertical

sync

pulseshaveapproximately

35

times

the

duration

of

horizontalsync).

In

thismanner,

the

hori-

zontal-sweep

generator

is

controlled

bythe

short-

time

horizontalsyncpulses,while

the

vertical-

sweepgenerator

is

controlled

bythe

longer

ver-

tical

sync

pulses.

The

sweeps

are

generated

by

hard-tube

blockingoscillators,amplified,

and

transformer

coupled

tothe

deflection

coils

ofthe

picturetube.

Because

the

horizontalsweepoccurs

262Va

times

as

fast

asthe

verticalsweep,

the

horizontal-sweep

output

is

connected

to an

additionalstagecalled

the

horizontal-controlstage.Thisstagecontri-

butes

greatly

tothe

linearity

and

reliability

of

SYNC

PULSE

OUTPUTCURRENT

(NOTE

UNIFORM

AMPLITUDE)

VIDEO

SIGNAL

SYNC

PULSEINPUTVOLTAGE

(AMPLITUDE

AND

VARIATIONS

EXAGGERATED

TO

ILLUSTRATE

CLIPPER

ACTION)

SIGNALVOLTAGEINCREASEBEYOND

•—THIS

VALUE

PRODUCES

NO

FURTHER

INCREASE

IN

OUTPUTSIGNAL

SIGNALVOLTAGEDECREASEBEYONDTHIS

VALUEPRODUCES

NO

FURTHER

DECREASE

IN

OUTPUTSIGNAL

the

horizontalsweep,acting

asan

automatic

damper

or

booster

as

required

forthe

instan-

taneousconditionsexisting

atany

portion

ofthe

sweepvoltage.

THE

POWER-SUPPLIES

SECTION

The

high-voltage

(7,300-volt)

supply

forthe

picturetube

is

provided

by

utilizingpart

ofthe

horizontal-sweep

output.

The

horizontalreturn

sweep

or

kick-back

is

very

fast,

and

therefore

generates

a

veryhighinducedvoltage.

The

hori-

zontal-sweep

output

transformer

ofthe

Model

48-1000

hastwo

specialwindingsadded

tothe

core.

Oneof

thesewindingsacts

asan

auto-

transformer,

coupling

the

kick-backvoltage

to

the

plate

ofthe

high-voltagerectifiertube.

The

otherwindingsupplies

thefilament

voltage

to

thistube.

By

thisarrangement,

the

necessaryhigh

voltage

is

securedfrom

the

horizontal-sweepkick-

back,

andatthe

same time

the

high-voltage

sup-

plyis

mademuchsafer,

in

that

the

current-

capacity

ofthe

circuit

is

limited

toa

fraction

of

a

milliampere.

The

plate-voltagesupplies

forthe

remainder

of

the

televisionreceiver

are

obtained

from

a

pair

of

5U4Grectifiersconnected

for

full-wave,

high-

current

rectification,withconventional

filtering.

TP-2665-K

TP-748

FIGURE

20.

SYNCSEPARATIONPRINCIPLE.FIGURE

21.

POWER-SUPPLY

SECTION,

SCHEMATIC

DIAGRAM.

14

MODEL

48-1000

Safety

devicesincorporated

in

Model48-1000

includeautomaticopening

ofthe

primarycircuit

when

the

backcover

ofthe

cabinet

is

removed,

and

when

the

picture-tubedeflection-coil

plug

is

disconnected

atthe

chassis.Thesedevicesprotect

the

servicemanagainstaccidentalshock,

and

pro-

tect

the

receiveragainstdamage

in

caseoperation

is

attemptedwith

the

loaddisconnected

from

the

sweepcircuits.

-

^

THE

PHILCOMETHOD

OF

TROUBLE-SHOOTING

TELEVISION

RECEIVERS

The

Philco

Method

of

Trouble-Shootingtele-

visionreceivers

is

based

ona

logical

and

thor-

oughtrouble-shootingprocedure.

Haphazard

testingwastestime

and

oftencauses

the

service-

man

to

overlook

the

lessobviouscircuittroubles.

The

followingprocedure

is

suggested

asan

effi-

cient

method

for

testingtelevisionreceivers.

The

basis

ofthe

Philcoprocedure

isthe

Philco

Test-Point Method.

The

televisionreceiver

is

considered

as

beingdividedinto

five

functional

sections:Section

1,the

powersupply;Section

2,

the

audio

or

soundchannel;Section

3,the

radio-

frequency

stages;

Section

4,the

videochannel;

Section

5,the

sweepcircuits.

The

overall

schem-

atic

andthe

sectionalbaselayouts

are

symbolized

accordingly

and

testpoints

are

assigned

to

each

section.

Eachsection

hasoneor

more

major

test

pointsindicated

bya

numeralwithin

a

star.

By

makingtests

at

these

major

points,

the

trouble

can

be

localized

toa

particularsection.

A

nor-

mal

indication

ata

major

testpointclears

a

large

block

of

circuitsfromsuspicionwithoutfurther

testingwithinthatblock.

In

addition

tothema-

jor

testpoints,eachsection

haskey

testpoints

indicated

bya

letterwithin

a

blackdisc.

Ifan

abnormalindication

is

obtained

ata

major

test

point,

the

defective

stage

is

isolated

by

testing

at

the

key

testpointsassociatedwith

the

major

test

point.

The

defectivepartthen

canbe

located

by

voltage

and

resistancemeasurements

ofthe

com-

ponentswithin

the

isolatedstage.Supplement-

ingthe

Test-PointMethod

isthe

PhilcoVisual-

Analysis

Method.Practically

allthe

troubles

which

occur

ina

television receivercauseabnor-

mal

indicationseither

onthe

picturetube,from

the

loudspeaker,

or

both.

By

visuallyanalyzing

the

receiverperformance,

the

trouble

in

many

in-

stances

maybe

localized

toa

particularsection

of

the

receiverwithoutgoingthrough

the

complete

Test-PointMethod.

The

followingexamples

of

such

analysis

areofaidin

applyingthismethod.

Many

ofthe

servicecomplaints

canbe

corrected

inthe

user'shome.

Ifthe

user'scomplaintindi-

catesthat

the

receivercannot

be

turned

on

with-

TROUBLE

INDICATION

Picture

tube

has

only

a

bright

horizontal

barof

light.

No

video,

but

audio

is

good,

and

raster

appears

on

picture

tube.

Audio

good,

but

picture

tube

un-

lighted.

Set

completely

dead.

(No

video

or

audio.)

Picture

is

"S"

shaped

on

side.

ANALYSIS

OF

TROUBLE

INDICATION

Defective

vertical-sweep

circuits.

Trouble

in

video

section.

Defective

high-voltage

power

sup-

ply,

or

horizontal

sweep.

Bend-

ing-coil

current

or

position

incor-

rect.

Defective

power

supply.

Defectiver-f,

mixer,

or

input

i-f

stage.

Hum

in

horizontal-deflection

coils.

REFERENCE

Refer

to

Section

5 of

trouble-

shooting

charts.

Refer

to

Section

4 of

trouble-

shooting

charts.

Refer

to

Sections

1 andS of

trouble-shooting

charts.

Check

power-supply

filters.Refer

to

Section

1 of

trouble-shooting

charts.

15

MODEL

48-1000

out

riskingfurtherdamage,inspect

thesetfor

odor

of

overheatedparts,signs

of

charredparts

and

insulation,shortedleads

and

brokenconnec-

tions.

Ifthe

complaintindicatesthat

the

receiver

can

be

turned

on

withoutcausingdamage,turn

onthe

receiver

andsetthe

channelselector

tothe

channel

ofa

stationthat

isonthe

air.

The

user's

complaintshouldserve

asa

guide

asto

when

to

look

forthe

trouble.Either

the

picture

orthe

sound,

or

both,

maybe

unsatisfactory.

If

both

are

poor,

useanAM

signalgeneratorconnected

tothe

antenna

jack

to

test

for

audiooutput

from

the

speaker

and

modulationbars

onthe

picture

tube.

If

both

are

satisfactory,check

the

antenna

system.

If

neithersound

nor

picture

is

satisfactory,

the

troublelies

ina

sectioncommon

to

both.Pro-

ceed

withisolating

the

troubleaccording

tothe

charts

for

Section

1,

PowerSupplies

and

Section

3,

R.F.

If

the

picture

is

satisfactory

butthe

sound

is

not,checkSection

2,

Audio,

as

given

inthe

chart

for

thatsection.

If

the

sound

is

satisfactory,

butthe

picture

is

unsatisfactory,

check

the

adjustment

ofthe

con-

trols

onthe

front

panel,behind

the

droppanel

andonthe

rear

ofthe

chassis.

If

none

of

these

controls

corrects

the

trouble,

usethe

testpro-

cedure

inthe

charts

for

Section

4,

Video

and

Sec-

tion

5,

Sweep.

TEST

EQUIPMENT

The

followingtestequipment

and

parts

are

required

to

perform

the

trouble-shootingtests

by

the

test-pointmethod:

VTVM

(or

20,000-ohms-per-volt

voltmeter)

with

10,000-volt

multiplier

OSCILLOSCOPE

SIGNALGENERATORS

Generator

A.

Audio-signalgenerator.

Generator

B.FM

signalgenerator.Center

frequency

range

20

me

to30

me.

Sweeprange

— 250kc.

Generator

C.AM

signal generator.Carrier

frequency

range

60

me

to72

me.

Generator

D.AM

signalgenerator.Carrier

frequency

range

20

me

to30

me.

PARTS

.1-mf

600-volt

papercondenser.

150,000-ohm

2-wattresistor.

15,000-ohm

2-wattresistor.

SECTION

1-

TROUBLE

SHOOTING

VTVM

or

20,000-ohms-per-voltvoltmeterused

for

steps

1

through

6.Usea

20,000-ohms-per-volt

voltmeter

and

multiplier

for

step

7.

STEP

1

2

3

4

TEST

POINT

^*y

+240-volt

bus.

/A

115-volt

a-c

trans-

^^

former

input.

|Sv

Transformer

out-

^^

put.

(Remove

5U4G

rec-

tifiers)

/S|

Rectifier

output.

"

(Replace

5U4G

rec-

tifiers)

NORMAL

INDICATION

+

245

voltsd.c.

110—120

volts

a.c.

750

volts

a.c.

+360

voltsd.c.

ABNORMAL

INDICATION

High

voltage

Low

voltage

No

voltage

Low

voltage

No

voltage

No

voltage

Low

voltage

High

voltage

Low

voltage

No

voltage

POSSIBLE

CAUSE

OF

ABNORMAL

INDICATION

If

normalindication

is

obtained,

proceed

to

step

8.

Incorrect

powersource.

•Switch

SI

00.

Plug

PI

00.

Jack

J100.

Power

cableW100.

J500.

P500.

T100

defective.

T100

defective.

Shorted

filament

circuit.

Open

LI

00,

R544,

R100.

Defective

5U4G.

Open

C102.

Short-

ed

C102,

C101B,

C101A,

C221B.

Shorted

C102.

Open

R524.

16

MODEL

48-1000

SECTION

1 -

TROUBLE

SHOOTING

-

Continued

STEP

5

6

TEST

POINT

4S\e

supply

>*s»

Filter

resistorout-

W

Put

NORMAL

INDICATION

—12

voltsd.c.

+

245

voltsd.c.

ABNORMAL

INDICATION

High

voltage

No

voltage

Low

or

high

voltage

POSSIBLECAUSE

OF

ABNORMALINDICATION

Open

R524,R525,

L501.

Shorted

C103.

Trouble

notin

thissection.

** *

DANGERHIGHVOLTAGE

* * *

7

>*sy

High-voltage

\£/

anodesupply

7300

voltsd.c.

No

voltage

Low

voltage

Defective

1B3GT.

Shorted

C100.

Horizontal-sweep

circuit.

Picture-tube

assembly.

Open

C100.

Defective

or

incorrect-

ly

adjusted

sweep.

FIGURE

22.

BOTTOMVIEW.SHOWINGSECTION

1

TEST

POINTS.

TP-2645-l

17

MODEL

48-1000

SECTION

2-TROUBLE

SHOOTING

Set

the

VOLUMEcontrol

to

maximum

andthe

TONE

control

fully

clockwise.

Generator

A —

Audio-signalgenerator.

Generator

B — FM

signalgenerator,

setto

22.1

me.

STEP

1

2

3

4

5

6

7

TEST

POINT

>*^

Input

to1st

audioi.f.

Vu

Z200.

(Generator

B)

Jfc

Grid

of7B5

audio

out-

^"^

put.

(Generator

A)

/S)

Grid(pin

6)7B41st

^^

audio.

(Generator

A)

AAFC

test

jack

J200.

^^

(Generator

A)

/Sv

Grid(pin

6)7W72nd

*~

audioi.f.(Generator

B)

A

Grid(pin

6)of1st

audio

^

i.f.(Generator

B)

^Ay

Input

to1st

audioi.f.

\2/

Z200.

(Generator

B)

NORMAL

INDICATION

Loud,

clearaudio

out-

pu'i.

Loud,

clearaudioout-

put.

Loud,

clearaudioout-

put.

Clearaudio

output

not

as

loud

asin

step

3.

Loud,

clear

audio

out-

put.

Loud,

clearaudioout-

put

Loud,

clearaudioout-

pui.

POSSIBLE

CAUSE

OF

ABNORMAL

INDICATION

Trouble

in

thissection.

Defective

speaker,

T200,C222,

7B5

tube.

Open

C221A.

Open

C223,

R218.

Defective

7B4

tube.

Shorted

C214,

C215,

C213.

OpenC216,

R212,

C217.

•

Defective

R213.

Defective

6AL5

discriminatortube,

7W7

tube,

Z202.

Open

L204,

R208,R207,R206,C208,

C206.

Shorted

C210,

C208.

Defective

7W7

tube,Z201.

Open

R204,R203,C204,

R202,

L203.

Shorted

C205,C204.

DefectiveZ200.

VERT.

HOLD

FIGURE

23.

BOTTOMVIEW.

SHOWING

SECTION

2

TEST

POINTS.

TP-2665-C

18

MODEL

48-1000

SECTION

3-TROUBLE

SHOOTING

Set

the

ChannelSelector

to

channel

No.3.

(Usechannel

No.3

coils

in

turret.)

Generator

C — AM

signalgenerator,

setto

audio-channel

frequency.

Voltmeter

—

(VTVM

or

20,000-ohms-per-volt

meter.)

Use

1000-ohm

resistor

in

serieswithnega-

tive

lead

of

20,000-ohms-per-voltmeter.

STEP

1

TEST

POINT

j*y

Loose

couple

to

V-4

antenna

at

J300.

(Generator

C)

NORMAL

INDICATION

Loud,

clear

audio

output.

ABNORMAL

INDICATION

Weak

orno

out-

put.

POSSIBLECAUSE

OF

ABNORMALINDICATION

Trouble

in

thissection;proceed

to

step

2.

FIGURE

24.

BOTTOMVIEW.

SHOWING

SECTION

3

TEST

POINTS.

TP-2665-D

19

MODEL48-1000

SECTION

3-TROUBLE

SHOOTING-Continued

STEP

2

3

4

5

TEST

POINT

/!%

Connect

voltmeter

to

pins

6 and 7 of

localoscillator.

/Sk

Couple

to

mixer

^"^

grid(pin

1).

(Gen-

erator

C)

/&

Couple

tor-f

grid

(pin

1).

(Generator

C)

*^y~

Loosecouple

to

WU

antenna

at

J300.

(Generator

C)

NORMAL

INDICATION

2.6

voltsnega-

tive

bias.

Loud,

clear

audioouput.

Loud,

clear

audio

output.

Loud,

clear

audiooutput.

ABNORMAL

INDICATION

No

bias.

Weak

orno

out-

put.

Weak

orno

out-

put.

Weak

orno

audiooutput.

POSSIBLE

CAUSE

OF

ABNORMAL

INDICATION

Defective

6J6

tube,

Z300.

Open

L302,

R305,

R304,

C303.

Shorted

C303,

C304,

C302.

Local

oscillator

off

frequency.

Defective

BAGS

input

i-f

amplifier

tube,6AG5mixertube,

Z400.

Open

R403,

R315,

R314,

R405,

R404,

R406,

R200.

Shorted

C404,

C318,

C203,

R406,

C309,

C317.

Defective

GAGS

r-f

amplifiertube,

Z300.

Open

R312,C309,R310,R311.

Shorted

C316,

C320.

Defective

Z301.

SECTION

4-TROUBLE

SHOOTING

Set

the

BACKGROUND

control

so

raster

is

faintly

visible

on

picturetube.

Setthe

CONTRAST

control

fully

clockwise.

Generator

A

—

Audio-signalgenerator.

Usea

.1-mf

condenser

in

series

with

signal

lead.

Generator

D — AM

signalgenerator

setto

26.6

me.

STEP

1

2

3

4

5

6

TEST

POINT

>*-y

Couple

to

plate

of

mixer

W

(pin

5).

(Generator

D)

M

Plate

of7C5

videoout-

put

(pin

2).

(Generator

A)

(D

Grid

of7C5

(pin

6).

(Generator

A)

A

Grid

of

6AG5

video

^^

amplifier

(pin

1).

(Generator

A)

(D

Plate—

Cathode

of

6AL5

(pin

1).

(Generator

D)

/j&

Grid

of2nd

video

i.f.

^

(pin

1).

(Generator

D)

NORMAL

INDICATION

Strong

alternatewhite

and

black

vertical

bars

on

picturetube.

Alternatewhite

and

blackvertical

bars.

Same

as

step

2

only

stronger.

Same

as

step

3

except

stronger

and

stable.

Same

as

step

2.

Same

as

step

2.

POSSIBLE

CAUSE

OF

ABNORMAL

INDICATION

Trouble

iri

thissection;proceed

to

step

2.

Defective

picturetube.

Open

C425,

L409.

Defective

7C5

tube.Open

R437,

R436,

R432,

R431,

R435.

Shorted

R435,

C422D,

C422C.

Defective

6AG5

videoamplifiertube.

Open

L408,

R428,

R429,

R425,

L411,

R426,

R427,

C423.

Shorted

C422B,

C422A.

Defective

6AL5

tube.

Open

L407,

C418,

R420,

L410.

Defective

6AG5

2nd

video

i-f

tube,

Z403.

OpenR413,R412,

L406,

R411.

ShortedC412,C411,

C428.

20

Philco 48-1000 User manual

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