Ampex 351 - Page 52

103 pages

Save Page as PDF

To Next Page

To Next Page

To Previous Page

To Previous Page

Loading...

6-4

TAPE

DRIVE

SYSTEM

The

tape

drive

system

is

composed

of

the

drive

motor,

the

extended

shaft

of

which

forms

the

capstan,

the

capstan

idler

arm

and

idler,

and

the

tape

guides

at

the

tape

entrance

and

exit

within

the

head

assembly.

The

purpose

of

the

tape

drive

system

is

to

transport

the

tape

across

the

heads

at

a

uni



form

speed

during

the

record

and

reproduce

processes.

By

means

of

a

hysteresis

synchron-

89-0131

89-0144

Issue

A

ous

capstan

drive

motor

(B501)

and

a

capstan

idler,

the

magnetic

tape

is

driven

at

a

constant

speed

after

power

has

been

applied

to

the

equipment

and

the

PLAY

button

is

pressed.

(The

drive

motor

has

two

sets

of

windings

to

provide

two

tape

speeds,

either

of

which

can

be

selected

at

TAPE

SPEED

toggle

switch

S503).

After

the

POWER

switch

at

the

electronic

assembly

has

been

placed

in

the

ON

position

and

the

tape

is

threaded

actuating

the

safety

switch,

the

drive

motor

operates

continuously,

its

capstan

awaiting

the

PLAY

command

(the

RECORD

function

is

selected

at

the

amplifier).

When

the

PLAY

button

is

pressed,

the

capstan

solenoid

(K501

)

and

the

brake

solenoids

(K505

and

K506

—

releasing

brake

pressure)

are

ener



gized.

The

capstan

solenoid

pulls

the

rubber

tired

capstan

idler

wheel,

which

is

mounted

on

a

swivel

type

arm,

against

the

tape,

causing

the

tape

to

make

firm

positive

contact

with

the

capstan.

The

tape

is

then

driven

at

a

constant

speed

across

the

head

assembly.

of

view

of

the

tape

take-up

turntable,

the

cap



stan

and

idler

action

is

feeding

the

tape

to

it.

The

tape

is

held

under

tension

here,

because

the

take-up

rate

exceeds

the

feed

rate

(a

tape

loop

will

be

thrown

on

the

right

side

of

the

capstan

whenever

any

malfunction

causes

the

feed

rate

to

exceed

the

take-up

rate).

If

a

tape

loop

is

thrown,

or

the

tape

breaks,

the

take-up

tension

arm

will

actuate

the

safety

switch

S501

and

stop

the

equipment.

The

take



up

tension

arm

is

not

a

part

of

the

tape

tension

system.

Its

function

is

to

takeup

tape

slack,

especially

when

starting,

and

to

operate

the

safety

switch.

The

reel

idler

assembly

smooths

out

tran



sients

in

the

supply

reel

system.

For

example,

when

starting

the

tape

in

the

reproduce

mode,

the

momentary

strain

transmitted

through

the

tape

to

the

tape

supply

turntable

when

the

capstan

idler

forces

the

tape

against

the

cap



stan

is

considerable.

Under

some

circum



stances,

this

impulse

tends

to

stretch

or

break

the

tape.

A

momentary

decrease

in

holdback

tension

might

be

sufficient

to

start

a

transient

oscillation

in

the

tape

tension

system

which

would

be

reflected

as

a

periodic

variation

in

the

distance

of

the

tape

from

the

heads.

This

varia



tion

might

be

of

sufficient

magnitude

to

appear

as

an

undesirable

fluctuation

in

the

signal

level

at

the

start

of

recording

or

reproduction.

The

reel

idler

arm

absorbs

most

of

the

starting

strain,

and

prevents

or

minimizes

this

type

of

oscillation.

The

reel

idler

pulley

and

flywheel

provide

additional

stability

in

the

tape

tension

system,

by

smoothing

out

such

transients

as

motor

torque

fluctuations

and

irregularities

due

to

faulty

tape

wrap

on

the

supply

reel.

This

is

accomplished

because

the

high

inertia

of

the

reel

idler

pulley

and

flywheel

effectively

isolate

the

reel

assembly

from

the

heads.

BRAKE

OPERATION

Smooth

brake

operation

is

extremely

im



portant

in

maintaining

proper

tape

tension

when

stopping

the

tape.

Because

the

holdback

tension,

supplied

by

the

trailing

turntable

motor

torque,

is

lost

after

the

STOP

button

is

pressed,

maintenance

of

tape

tension

then

be



comes

a

function

of

brake

operation.

The

braking

force

acting

on

the

turntable

from

which

the

tape

is

being

pulled

(trailing

turn



table)

in

any

of

the

modes

of

operation

must

exceed

the

braking

force

acting

on

the

turn



table

taking

up

the

tape

(the

leading

turntable)

to

prevent

tape

loops

forming.

One

end

of

the

brake

band

is

fixed

to

the

cross

head

by

a

roll

pin

and

two

socket

head

cap

screws

which

is

attached

to

the

anchor

mounted

on

the

brake

housing.

The

other

end

is

linked

to

the

brake

lever

by

a

drivelock

pin

and

is

free

to

move.

When

the

brake

solenoid

is

de-energized,

the

brake

tension

spring

acting

on

the

brake

lever

draws

the

brake

band

against

the

brake

drum.

If

the

brake

drum

of

the

supply

motor,

as

viewed

from

the

brake

housing

end,

is

rotating

clockwise

when

the

brake

band

is

applied,

the

frictional

force

will

cause

the

band

to

wrap

Related product manuals

Preview: Ampex 351 Series

Ampex 351 Series