Dyna FM-3 - Troubleshooting and Service Information; Troubleshooting Common Issues

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the

AC

outlet.

Connect

the

violet

lead

to

lug

#2

of

the

fuse

holder

(S).

2 ( )

Twist

together

the

black-white

and

the

violet-white

power

transformer

leads.

Connect

both

leads

to

lug

#1

of

the

five

lug

terminal

strip

(S-2).

When

using

the

240

volt

connection, a

one-half

ampere

slo-blo fuse

should

be

used

instead

of

the

one

ampere

fuse

recommended

for 120 volt

operation.

IN

CASE

OF DIFFICULTY

In

the

event

that

your

first

attempt

at

listening

to

your

Dynatuner

is unsuccessful, a

systematic

approach

to lo-

cating

the

difficulty will

save

you

much

time

and

trouble.

Because

90%

of

the

difficulties which

are

encountered

can

be

attributed

to

either

incorrect

wiring

or

to a

poor

solder

connection,

it

is

strongly

recommended

that

you

first

ask

someone

else

to

check

the

wiring

against

the

pictorial

diagrams,

as

frequently

one

person

will

make

the

same

error

twice.

In

the

course

of

trouble

shooting,

inspect

very

carefully

for

"bridges"

of

solder

from

one

point

to

another.

Also

recheck

for

correctness

of

component

positions

on

the

etched

circuit

boards.

Many

defects

of

this

type,

as

weIJ

as

faulty

components,

can

be

ascertained

by

voltage

measurements,

and

a

complete

voltage

chart

is

provided.

Any

deviation

of

20%

or

more

from

this

chart

(except

for

voltages

marked

~)

indicates

a

possible

error

or

com-

ponent

failure.

Examination

of

components

in

the

area

of

incorrect

voltage

(with

reference

to

the

schematic

dia-

gram)

should

help

to

uncover

the

difficulty.

For

purposes

of

simplification,

the

initial

trouble-shoot-

ing

suggestions

will be confined

to

the

basic

tuner

circuit

for

the

Multiplex

Integrator

does

not

usually

affect

mon~

reception.

The

volume

control

knob

should

be

pulled

"QtJT"

for

this

part.

Normal

radio

servicing

techniques

of signal

injection

and

signal

tracing

are

appropriate

for localizing troubles.

For

brst

alignment,

however,

the

procedure

specified

in

these

instructions

should

be

followed.

If

servicing

is

done

by

a qualified

technician,

he

can

expedite

alignment

by

setting

the

J.F.

transformers

for

peak

eye

deflection using

a

very low level 10.7

me

signal.

The

strength

of

this signal

should

be

just

strong

enough

to

actuate

the

tuning

eye,

but

not

so

strong

that

it

closes

it

to

its

normal

minimum

gap. As

the

alignment

proceeds,

it

will be

necessary

to

reduce

the

level of

this

test

signal

so

that

the

tuning

eye

accurately

indicates

the

alignment

peaks.

Discriminator

alignment

must

follow

the

technique

described

in

these

instructions.

Conventional

"sweep"

techniques

should

not

be used.

Drift,

or

shifting

of

the

tuned

signal

frequency,

should

be

cause

to

suspect

poor

mounting

or

soldering

of

C7

or

C8,

or

a

defective

6AT8A

tube.

If

the

dial

lamp

and

tubes

do

not

light

when

the

set

is

plugged

in

and

turned

on,

check

to

see

if

the

fuse is all

right.

Sometimes

a

fuse

may

appear

to

be

intact,

but

the

circuit

will

be

open

at

one

end.

A

continuity

test

at

the

prongs

of

the

line

cord

with

a

meter

will

show

if

the

fuse,

power

switch,

and

the

power

transformer

primary

winding

are

all

properly

connected

and

functioning.

If

the

one

ampere

fuse blows

when

the

set

is

turned

on,

remove

all

the

tubes,

install

another

one

ampere

slo-blo

fuse

and

try

again.

If

the

same

size

replacement

fuse

blows

20

when

all

of

the

tubes

ar(' removed,

the

trouble

lies

either

in

the

line

cord,

the

power

transformer,

or

in

heater

con-

nections

in

the

tuner.

Check

particularly

those wires con-

nected

to

the

5

lug

terminal

strip.

If

the

tubes

light,

but

not

the

dial

lamp,

the

lamp

may

be defective,

or

the

wires

which

lead

to

it

via

the

etched

circuit

board

may

be

open.

If

the

tubes

light

and

the

tuning

eye

tube

shows a

lighted

filament,

but

the

pye does

not

have

a

blue-gwen

glow

on

the

front

screen

(which

is visible

through

the

plastic

insert

in

the

front

panel)

check

the

wiring

around

the

tuning

eye

socket.

If

this

is all right,

the

fault

may

be

in

the power

supply,

and

the

rectifier

tube

V9

and

the

associated

wiring

should

be chpcked.

If

the

eye

glows,

the

power

supply

wiring

can

be

assumed

to be correct.

If

the

tuning

eye

does

not

defled

when

the

tuning

knob

is

turned,

the

difficulty is

probably

on

PC-7.

Check

the

6AT8A

tube

and

also wiggle

the

antenna

coil L1

to

make

sure

its

solder

connections

are

firm.

Frequently

difficulties in

the

I.F.

strip

(PC-8)

can

be

localized

by

touching

the

#1

pin

of

each

J.F.

tube

in

the

sequence

V6, V5, V4, V3. A noise

should

be

heard

each

time

the

# 1

pin

is

touched,

and

the

tuning

eye

should

deflect.

If

you

find a # 1

pin

which

does

not

produce

a

noise,

then

look for

the

difficulty

between

that

point

and

the

previously

tested

# 1

pin.

If

there

is

apparent

distortion

in

the

signal,

make

sure

that

this is

not

a

momentary

effect

because

of

poor

trans-

mission.

See

if

the

same

distortion

is

apparent

on

another

station.

If

it

persists,

compare

the

same

system

with phono-

graph

or

tape

as

a

different

program

source

to

see

if

the

effect

can

be localized to

the

tuner.

If

it

is definitely in

the

tuner,

it

may

be

caused

by

improper

discriminator

alignment,

and

this

portion

of

the

alignment

procedure

should

be

repeated.

Audio

distortion

is

also

an

effect of

"multipath

dispersion"-

reflections of

the

signal

by

build-

ings,

hilly

terrain,

etc., which

cause

effects

similar

to tele-

vision

"ghosts",

often

accompanied

by

reduced

separation

on

stereo

broadcasts.

Multipath

effects

can

be

reduced

only

by

improving

the

antenna

system-relocation,

reorienta-

tion,

or

replacement

with

a

more

directional

antenna.

If

the

tuner

operates

and

can

be

aligned,

but

has

hum

in

the

signal,

there

are

several

tests

to be

made.

If

the

hum

is

part

of

the

signal

and

disappears

when

the

volume

is

turned

down,

try

several

stations,

as

it

is possible

that

the

one

used

as

a

test

signal is

broadcasting

some

hum.

If

hum

occurs

on

all

stations,

the

6AT8A

may

he

faulty

and

should

b.e

checked

(preferably

by

substitution).

If

the

hum

per-

SISts, even when

the

volume

control

is

turned

down,

unplug

the

tuner

from

the

associated

equipment

and

see if

the

hum

disappears.

If

it

does

not,

the

fault

lies

in

the

associated

equipment.

If

it

does

disappear,

then

the

hum

may

be

caused

by

a

defective

ground

contact

in

one

of

the

audio

cables,

or

it

may

be

associated

with

V7

or

V72.

Check

the

12AX7s

by

substitution.

If

the

eye

deflects

as

the

tuning

dial

is

turned

this

is

an

~ndication

that

the

R.F.

stages

and

the

I.F.

stage~

are

work-

mg,

and

the

difficulty lies

either

in

the

discriminator

trans-

former

or

the

subsequent

audio

stages.

Working

backwards

from

the

audio

outputs,

touch

the

following

points

with

a

screwdriver

to

see

if

you

get a

pop

or

hum

through

the

speaker

when

the

tuner

volume

control

is

turned

up:

The

center

conductor

of

each

output

socket,

pin

#2

and

pin

#7

of V72,

eyelet

71,

pin

#2

and

pin

#7

of V7.

If

a noise is

not

heard

through

the

speaker

when

one

of

these

points

is

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