Telefunken M 204 E - Drive Mechanism Principles; Motor Belt Replacement; Tape Path Alignment Procedures; Feed;Take-Up Plates and Head Adjustments

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Feed

Plate,

left

Functional

Principles

of

the

Drive

Mechanism

The

unit

employs

a

round

profile

belt

drive.

The

symmetrical

shaded

pole

motor

drives

the

motor

belt,

which

in

turn

drives

two

intermediate

wheels

and

a

switching

wheel.

The

flywheel

disc

is

driven

from

this

switching

wheel,

via

the

drive

belt.

For

tape

drive

speed

changeover,

a

switching

rocker

throws

the

drive

belt

into

the

other

groove

on

the

switching

wheel

and

on

the

flywheel

disc.

~

Belt

Interrnediate

Wheel

Motor

Switching

Wheel

Tape

Drive

Belt

Flywheel

Disc

Fig.

4

Schematic

depiction

of

the

drive

mechanism

Important:

The

tape

drive

speed

may

be

switched

over

only

when

the

unit

is

switched

on.

Recording

—

Playback

When

the

tape

drive

button

is

pressed,

the

stop

brakes

release

the

feed

and

take-up

plates.

The

friction

wheel

is

pulled

in

between

the

flywheel

disc

and

the

supporting

plate

of

the

right

take-up

plate

assembly,

so

that

it

drives

the

right

brake

plate

via

a

slipping

clutch.

On

the

left

feed

plate

assembly,

an

auxiliary

brake

restrains

the

supporting

plate,

so

that

the

left

slipping

clutch

becomes

effec-

tive.

This

slipping

clutch

consists

of

the

supporting

plate

and

the

felt

ring

below

the

brake

plate.

Fast

Forward

Drive

When

the

fast

forward

drive

button

is

actuated,

the

stop

brakes

release

the

feed

and

take-up

plates.

The

auxiliary

brake

is

applied

to

the

left

supporting

plate.

The

rubber

coating

of

the

right

intermediate

wheel

is

pressed

against

and

thus

drives

the

right

brake

plate.

Excessive

starting

tension

is

not

exerted

on

the

tape,

because

this

is

prevented

by

the

tape

protection

coup-

ling

between

the

brake

plate

and

the

slip

plate.

Rewind

Drive

Once

again,

the

stop

brakes

release

the

feed

and

take-up

plates

when

the

rewind

button

is

actuated.

The

brake

releases

the

left

supporting

plate

and

the

rubber

coating

of

the

intermediate

wheel

is

pressed

against

and

drives

the

left

brake

plate.

The

tape

protection

coupling

on

the

left

plate

serves

the

same

function

as

the

one

on

the

right

plate.

The

tape

tension

is

established

with

the

felt

brake

below

the

right

take-up

plate.

Replacement

of

Componets

and

Mechanical

Adjustments

Replacing

the

Motor

Belt

After

unhooking

the

tension

spring,

fold

up

the

switching

rocker

towards

the

head

carrier

plate.

Twist

the

leaf

spring

from

its

normal

resting

position

towards

the

head

carrier

plate

and

place

the

motor

belt

into

the

upper

groove

of

the

switching

wheel,

over

the

intermediate

wheels

and

into

the

lower

groove

of

the

fan

wheel

(for

60

Hz

operation,

into

the

upper

groove

of

the fan

wheel).

Make

sure

that

the

motor

belt

runs

approximately

parallel

to

the

chassis

into

the

groove.

Replacing

the

Drive

Belt

Take

off

the

right

take-up

plate

and

screw

out

the

three

fixing

screws

1,

2

and

3

(Fig.

5)

of

the

head

carrier

plate.

Pull

off

the

head

carrrier

plate

upwards

from

the

drive

capstan

(the

plastic

prismatic

bearing

of

the

drive

capstan

remains

in

the

head

carrier

plate).

After

unhooking

the

tension

spring,

take

out

the

switching

rocker,

and

take

the

motor

belt

off

the

switching

wheel.

Insert

the

new

drive

belt,

first

of

all

into

the

upper

groove

of

the

flywheel

disc,

then

into

the

lower

groove

of

the

switching

wheel,

with

the

tape

drive

speed

selector

set

to

19

cm/s.

Reinsert

the

switching

rocker

and

make

sure

that

the

drive

belt

rests

in

the

two

cut-aways.

Remount

the

head

carrier

plate

onto

the

drive

capstan.

Check

that

the

plate

rests

securely

on

its

supports

and

that

the

lever

of

the

pressbutton

assembly

lies

in

front

of

the

slider

(F)

of

the

plate.

Tighten

the

screws

in

the

order

1,

2,

3

as

specified

on

Fig.

5.

If

the

dust

protection

ring

has

become

displaced,

press

it

down

only

to

such

an

extent

that

a

clearance

of

about

0.5mm

still

remains

with

respect

to

the

prismatic

bearing

in

‘the

head

carrier

plate.

The

dust

protection

ring

must

not

touch

the

upper

edge

of

the

rubber

roller.

If

the

dust

protection

ring

scrapes

against

the

bearing

or

against

the

rubber

rolier,

this

would

produce

pitch

fluctuations

and

rumble.

Clean

the

drive

capstan

with

isopropyl

alcohol.

Carry

out

a

functional

check.

Tape

Alignment

The

feed

and

take-up

plates,

the

tape

guides

and

the

record/play-

back

head

as

well

as

the

erase

head,

are

adjusted

to

a

uniform

height

in

the

factory.

As

a

rule,

readjustment

is

necessary

only

after

components

have

been

replaced.

Feed

and

Take-Up

Plates

The

feed

and

take-up

plates

can

be

adjusted

in

height

with

respective

sliders.

They

should

be

adjusted

such

that

the

tape

runs

in

centrally

between

the

flanges

of

the

tape

spools.

Erase

Head

The

height

of

the

erase

head

can

be

adjusted

by

turning

the

screw

(G).

The

adjustment

should

be

made

such

that

the

upper

edge

of

the

core

extends

about

0.1

mm

above

the

upper

edge

of

the

tape.

Record/Playback

Head

The

height

of

the

record/playback

head

can

be

adjusted

with

two

grubscrews

(C).

The

upper

edge

of

the

core

packet

in

the

record/playback

head

should

be

flush

with

the

upper

edge

of

the

tape.

Furthermore,

it

is

important

to

make

sure

that

the

head

face

is

vertical,

i.

e.

that

it

is

aligned

parallel

to

the

drive

capstan.

After

every

mechanical

readjustment,

the

head

must

be

rocked-in

(screw

D)

with

the

help

of

a

test

tape.

Rubber

Roller

Pressure

Lever

(RP-Lever)

Clearance

of

Roller

Holder

When

the

tape

drive

button

(start

button)

is

pressed,

the

long

thrust

rod

for

the

head

carrier

plate

mechanism

is

moved

via

an

actuator

bracket.

It

is

thereby

important

to

make

sure

that

the

lower

sheet

metal

section

of

the

RP-lever

rests

firmly

against

the

second

tape

guide

(with

slight

excess

excursion)

when

the

start

button

is

pressed.

If

this

condition

is

not

satisfied,

then

the

excursion

of

the

thrust

rod

must

be

adjusted

accordingly,

by

inserting

metal

washers

between

the

actuator

bracket

and

the

thrust

rod.

The

spring-loaded

roller

holder

should

have

a

clearance

of

about

1.

mm

with

respect

to

the

right

edge

of

the

RP-lever

in

the

pressed-in

state,

in

order

that

the

rubber

pressure

roller

can

operate

without

hindrance.

On

the

right,

the

clearance

of

the

roller

holder

with

respect

to

the

rapid

stop

lift-off

device

should

be

about

2

mm.

a

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