TANDBERG 62 series, 64 series Service Manual

January 1967

TANDBERG

TAPE.RECORDER

Models 64x

and 62x

Alignment

instruction

for

heads

and

electronics

Preface

The models 64x

and

62x

are improved versions

of has been introduced

to improve the frequency

re-

the earlier models

64-62

and this

alignment instruc-

sponse and the signal

to noise

ratio.

tion is

an appendix to

the

service

manual

for

model

The

oscillator has

been redesigned

and

fully transis-

64:-62.

lt

covers the special

head alignments

and torized. Certain minor

changes have been

introduced

electrical adjustments necessary for

model

64x

and

in the equalization circuits, mainly changes

of com-

62x.

ponent

values. A

microswitch

is

further introduced

in

the

bias

circuit

to

reduce

the

bias

in

1.7/e i.

p.s.

The models

64x and

62x

have the

same operation

tape speed. This switch

is

operated

automatically

by

facilities

as 64-62. A new,

and

separate

bias head

the

speed

selector

mechanism. See fig. 3.

Ti.^d.{*..q

r=r=rErlEr/

TANDBERGS

RADIOFABRIKK

A/S

OSLO

NORWAY

1.0 Alignment
It

is important that

the

contact

between

the

tape and

the

heads

on

the tape

recorder is

good.

To

obtain

this

contact the

tape should be run through the

tape

recorder

5-10 times at normal speed

to have the

tape

polished

before measuring

the

frequency

re-

sponse and

the signal

to noise

ratio.

1.0.1 Demagnetizing
Demagnetize

the heads and adjacent

parts

before

aligning

the heads.

1.0.2. The mounling

plate

lor the heads

The

height of the mounting

plate

for the

heads

(15.4)

is

aligned by the adjustment screw

at the

rear

of

the

playback

head. Move

the operating lever

slowly

to

normal forward

drive

with

a

tight

tape

inserted.

Align

the

height of

the

mounting

plate

for the heads

until

the

tape

runs

equidistant

from the

flanges of the tape

guide

(79,2).

1.0.3

The adjustable tape

guide

Set the

operating lever in

normal forward

drive

with

tape

inserted

and depress the

push-button

lll. Align

the

adjustable tape

guide

(79.3)

until

the

tape

runs

equidistant

from the

flanges

of

the adjustable tape

guide.

Repeat

1.0.2.

2.O Adjustment of

the

oscillator and bias head

circuits.

2.0.1 Insert

one

10 ohm resistor

in series with each

bias head half to

ground

and

connect

a V.T.V.M.

across each

resistor.

2.O.2

R 609 and R 612 is turned up

to

1 o'clock

posi-

tion while R607 and R610 are

set

to approx. 11

o'clock. Rel. fig.

3.

2.0.3 Set

the

tape

recorder

to stereo recording and

the

speed selector

to

7tlu i.p.s.

2.0.4 Use a

calibrated

long wave

receiver, frequency

meter or

frequency

counter for the indication

and

adjust the oscillator

frequency

by

C 610 until f/osc.

=

85.5

kc/s.

2.0.5 Set the

tape recorder

for mono recording

CH

1

and

the

speed selector to 7tlz

i.p,s.

2.0.6

Adjust

the oscillator

frequency with

L601

F/osc.

will

then

be

85.5 kc/s.

2.0.7

Set

the

tape

recorder for mono recording CH 2.

2.0.8 Readjust L

601

to

compromise

if necessary. The

osc.

frequency

deviation between mono recording

CH 1, CH 2 and stereo

should

be less

than 2 kc/s.

The deviation should be indicated

with

frequency

meter, long wave

receiver or

frequency

counter.

2.0.9

Adjust

C 602

and

604

to max. reading on the

V.T.V.M.

(between

100 mV and 400 mV).

3.0

Head

alignment

and track

control

with

Tandberg

Test Tapes,

Model

64x

3.1.

The

playback

head

3.1.1 Connect

one

V.T.V.M.

to each

CATHODE

FOLLOWER

output.

3.1.2 Height

alignment:

Play back

the test tape

No. 1.

This is

a full track

pre-recorded

tape with

1000

c/s recorded

atTt/zi.p.s.

tape speed.

The record level of the

exact

area

corresponding

to track 3 is

reduced

30 dB.

Adjust

the height of the

playback

head

until

minimum output

is

botained on a

V.T.V.M. from

track

3

(ch.

2).

3.1.3

Azimuth alignment:

Play back the test tape No.

2. This is a full track

pre-recorded

tape with 10.000

cls al 71lz i.p.s. tape

speed.

Adjust the

azimuth

position

of

the

playback

head until maximum reading

is obtained on both

output

meters.

3.1.4.

Lateral

alignment:

Check

the

lateral

position

of

the

playback

head by

pulling

the

pressure pad

(59.5)

away

from

the erase

head when

the test

tape

No.

2 is

played

back.

The

output level

should not decrease more

than 3 dB.

Adjust the

lateral

position

of

the

playback

head, is

necessary,

by turning the head mounting

plate.

Re-

adjust the

azimuth

position.

3.2

The

record

head.

3.2.1

Adjust

the horizontal

position

of the bias

head

until

the

head is in

center of the record head. Ref.

fig. 1.

3.2.2

Adjust

the height

of

the

bias head until

the

tape

runs freely

in the

groove

in front

of the

bias

head.

3.2.3

Height

alignment:

The

record

head is

set

in a

preliminary position

where

approx.

0.1 mm

(.0025")

of

the

lamination for the

upper track is visible

above the tape. The

position

of

the record

head can

be

inspected

by using the iron

powder

method

(Magna-See).

Record all

four tracks

on the

tape

and dip the tape in the solution. The

pattern

on the tape will

show il the

position

of the

head is

correct.

Readjust

if necessary.

3.2.4

Azimuth

alignment:

Connect

a signal

generator

to the HI-LEVEL inputs

CH1 and

CH2,

and

two

V.T.V.M.

to

the

CATHODE

FOLLOWER

outputs

CH1

and

CH2.

Make a

stereo

recording in

B-test al 7t/z i.p.s. of

a

15.000 c/s

signal.

Adjust

the azimuth of the record

head to

max. reading

on

the

output

meters.

The out-

put

level

should now be approx. 100 mV with the

playback

volume controls

to max.,

readjust

the record

gain

controls until this is obtained and

check

the

azimuth

position

of the record head.

3.2.5

Lateral

alignment:

Check the

lateral

position

of the

record head

by

pulling

the

pressure pad

(59.5)

away

from

the erase

head during the recording.

The output level should

not

decrease

more

than 3

dB.

Adjust the

lateral

position

of the record head, if necessary, by turning

the head mounting

plate.

Recheck the height and

azimuth

position

of

the head. Ref.

para.

3.2.3 and

3.2.4.

3.3

The

bias

head.

3.3.1

Heighl

alignment:

Connect

two

V.T.V.M.

directly across the

recording

heads.

Set

the tape recorder to

stereo

recording at

71 lz

i.p.s.

and turn both

playback

volume controls

down

to

0.

Adjust the height of

the

bias head

by the

height

adjustment screw

(ref.

fig.

1) until max. reading is

obtained

on

both

V.T.V.M.

Check

that

the

tape

runs

freely in the

groove

in front

of

the

bias head and

that

there

is

sufficient

clearance between the bias

head and

the

mounting

plate

for

the record head.

The height

position

of

the

bias head is not

critical,

and

if

the clearance between

the bias head and the

mounting

plate

for the record

head is

insufficient,

raise

the bias head slightly.

3.3.2

Horizontal

alignment:

Connect two V.T.V.M.

to both

CATHODE

FOLLOWER

outputs, and

connect a signal

generator

to the Hl-

LEVEL inputs

CHI and CH2.

Set

the

tape recorder

to

stereo recording al 71lz i.p.s.

and

turn

both

play-

back volume controls

to max.

Record

a 1000

c/s

signal.

Untighten the

fixing

screw

for

horizontal adjustment

(ref.

fig.

'1)

and

move the

bias head from the

extreme

Ieft

position

towards

the recording head

until

max.

reading

is

obtained

on both

V.T.V.M. The output level

should now

be approx..5V,

readjust

the record

gain

controls until this is

obtained and check

the

horizon-

tal

position

of

the

bias head. After

one has assured

that the

horizontal

position

is

correctly

adjusted,

tighten the

adjustment

screw making

sure that

the head is

not being moved.

This is eventually

indicated

by a loss

of the output level.

A fine-adjustment

of

the

bias current is

obtained by

the

pot.meters

R609

(CH1)

and

R612

(CH2).

Adjust

R

609 and R

612 until max. reading

on

the optput

meters

are obtained.

3.4 The

erase head.

3.4.1

Height adjustment:

The erase head is

set

in

a

preliminary position

where

approx.

0.25 mm

(.01")

of

the

ferrite core for the

upper track

of

the

erase head is visible

above the

tape. Insert

the test tape No.

9 and

record

a 1000

c/s

signal from the

generator

on

ch. 2 at maximum re-

cording level. Dip

the

tape in

the Magna-See

solution

and

check that the re-recorded

track lies

in

center

of

the

erased track. Make

sure that the

erase head

does

not

erase any

part

of

the adjacent tracks.

3.4.2 Azimuth

alignment:

Align the

azimuth

position

of the

erase head by the

azimuth adjustment

screw. The

erase head

should

be

parallel

with the

mounting

plate

for the

heads

(15.4).

The

azimuth

position

of the erase head is not

critical.

3.4.3 Lateral

alignmenl:

Turn the

head mounting

plate

for the

erase head, until

the front

of

the

head is

parallel

to the

pressure pad.

3.5 Model

62x.

10

000- 5000 - 1C00 - 100-

50-250 c/s

recorded

at71/t

i.p.s. tape

speed. The tape

conforms

with the N.A.B.

standards. The

output tolerance is

-+

2

dB

for

all

frequencies.

The

difference in

level

between the

two

channels

should be less than 3 dB.

4.2

Adjustment

of the

playback

amplifiers:

Play

back

the test

tape No. 4 with

the output

volume

controls

to maximum. This is

a full track

prerecorded

tape

with 400 c/s

at71/z i.p.s. tape speed.

Ad.just the

potentiometers

R233

(CH

1)

and

R234

(CH

2)

until

the

reading

on the

output meters

are 1.3V.

5.0 Adjustment of

the record

current

(A-B

test) and

the

electronic

beam indicators.

Make

sure

that

all adjustments

under

paras

1.0,

2.0

and 3.0 are made before

proceeding

with these ad-

justments.
Connect a

signai

generator

to

both Hl-LEVEL

inputs

and two V.T.V.M.

to both

CATHODE

FOLLOWER

out-

puts.
Record

a 4O0

cls signal in

stereo A-test, with both

playback

volume

controls to max. at 7tlz i.p.s. Adjust

the record levels

by the record

gain

controls

until

the output

levels

are

1.5 V. Depress

the

push-buttons

lV and V

(stereo

B-test) and

adjust

the

record current

by

R115

(CHl)

and

R116

(CH2)

until the readings

on

the output meters

are 1.5 V.

Adjust

R 137

(CHl)

and R 138

(CH2)

until the elec-

tronic

beam indicators

are

closing.

Release the

push-

buttons lV

and V

(stereo

A-test)

and

check

that the

readings

still are 1.5 V on

the output

meters.

6.0 Head alignment

without Tandberg

Test Tapes.

6.1 The

playback

head.

6.1.1 Height

alignnnent:

The

height

of the

playback

head is

aligned by the

height adjustment

screws. The upper edge

of

the tape

shall

run flush with

the

upper

part

of the airgap

for

channel

1.

6.1.2 Azimuth

alignmenl:

Play

back a standard

azimuth

alignment tape with a

V.T.V.M.

connected to

each cathode follower

output.

Adjust the

position

of

the

playback

head by the

azimuth

adjustment

screw,

until

maximum

reading is

obtained on the output

meters.

6.1.3 Lateral

alignment:

Pull

the

pressure

pad

(59.5)

away from the

erase head

when

the

standard azimuth alignment

tape is

being

played

back. The

output

level

should not

decrease

more

than 3 dB. Adjust

the

lateral

position

of

the

playback

head, if

necessary,

by turning

the head

mounting

plate.

All

the

alignments

specified

in chapters

3.1, 3.2, 3.3,

6.2

The

record

bead.

and

3'4 are valid for

model 62x with

the exception-o1

iorro*'in"l

instructions

given

under

para3.z.

paragraph

3.1.2 which

is

superseeded by 6.1.1

and

paragraph

3.2.3 is

superseeded by 6.6.2.

6.3

The

bias head.

4.0

control

and adiustment

ol

playback

amplifiers,

Follow

the instructions

given

under

para

3'3'

with

Tandberg

test tapes.

6.4 The erase

head.

4.1

Control of

the

playback

amplifier:

6.4.1 Height

alignment:

Play

back the test

tape No.

3.

This

is

a full track

pre-

The

height

of the erase

head is

aligned by

the height

recorded

tape with the

following frequencies:250-

adjustment

screws. Approx.0.25

mm

(.01

")

of the