TANDBERG 12 Bedienungsanleitung

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Service manual

MNDBERG

Tape recorder

modell 12

Preface

Thisservicemanualcovers

the Tandbergtaperecor-

der

models

l2-4 and12-2.fhe model

seriesl2 isa

fully transistorised,three speedstereo,

record

arrd

playback

unitwith two heads.lt is equipped

with

separaterecordand

playbackpreamplif

iers

and

sepa-

rate power amplifiers

for eachchannel.The power

output

amplifiersarerated

for l0 watts

each.

Themodel 12 -2 is the two-track

versionwhile the

model I

2-4 is the four-trackversion.The models

12-2 and )2-4 haveexaclly

the samemechanical

systemand

operatingcontrols.

We hopethot

everyoneconcerned

with our products

will find thisservicemanual

useful. April

1967

T'r

Contents

Technicol specificqlion, Tondberg tope recorder models

l2-4 ond l2-2 .

The function of the conlrols

The inpuf ond outpuf lerminols

The mechonism, detoiled descripiion ond odiusiment

instruciion

The operoling lever . .

4.I.1 The moior switch

1.1.2 lhe eccentric segment

4.1.3 The pressure wheel ossembly

4.1.4 The tope broke

4.1.5 The trip bor

4.2 The

turnfoble

ossemblies

^ 4.2.1 lhe supplyturnfobleossembly

r 4.2.2 lhe lope iight lension .

4.2.3 The

toke-upturntoble

ossembly

A.2.4 Horizontsl

ond veriicql olignmentsof the furntobles

1.3 Clulch olignments

4.3.1 Generol

4.3.2 Fost rewind

4.3.3 Fost

wind

4.3.4 Normql forword drive . .

4.3.5 Neutrol

4.3.6 Free

4.4 fhe motor pulley

4.4.1 Threoding of the rubber drive belt

4.5 The speed lronsfer wheel

4.6 Thelifting

mechonism..... .'.... '.. 19

5.2.1 The funclion selecior swilch

5.2.2 lhe speoker selector swilch .

5.2.3 Monourol recording on CHI or CH2 , .

5.2.4 Mixing during monourol recording

5.2.5 Stereo recording

5.2.5Monourol

ploybock,chonnel

I or 2 .. '....,.

5.2.7 Stereoploybock 33

5.2.8 Stereo

omplifier 33

5.2.9 Add o irock . 33

S.2,l0Sound

on sound 34

5.3 Heod

olignment

ond frock

conlrol

with Tondbergtest

tope 34

5.3.I The

Models

l2-4 and12-2 .......... 34

5.3.2 Themodel l2-2 35

1.0 3t

5.5

5.6

2.O

3.0

4.O

1.1

't0

'15

't5

't8

)

4.9 The momenlqry stort-stop feoture

4.10 The pressure pqd . . .

4.l l The oulomotic end sfop switch .

4.12 The revolulion counler .

4.13 Assembling the fop cover

5.0 The electroniccircuits,

detoiled descriplion ond odiusfmenl

instruction

5.1.1 lnpuls

5,'I.2 The record pre-omplif

ier

5.1.3 The FM multiplex-filter

5.1.4 The equolizing omplifier in record posiiion . '... ' 25

5.1.5 The equolizing omplifier in ploybock position . .. . 26

5.1.6 The equolizing omplifier in omplifier posilion . .. . 27

5.1,7 lhe power oulput omplifier 28

5.1.8 The ploybock pre-omplifier 29

5.1.9 The record level indicotor circuit .. 29

5,l.l0The oscillotor, bios ond erose circuit 29

5.l,ll The power supply 30

5.4 Heod olignment without Tqndberg test topes

5.4.1 Demognetizing

5.4.2 The odlustoble tope guides

5.4.3 The record/ploybock heod

5.4.4 The erose heod

Trock conlrol, model l2-4 without Tqndberg test lqPes . -

5.5,1 The record/ploybock heod

5.5.2 The erose heqd

Trock conlrol, model l2-2 without Tondberg lesi topes ..

5.6.1 The erose heod

5.6.2 The record/ploybock heod . .

Electrical

qdiustments for Tondberg tope recorder models

12-4 ond 12-2 . .

5.7.1 Adiustment of ihe Power outPuf omplifier

5.7.2 Adiusfment of the outpui level

5.7.3 The quiescent currenl .

5.7.4 Adiustment of the FM MX-filter

5.7.5 Control of lhe frequency response in omp' position

5.7.6 The boss conlrol

5.7.7 The ireble control

5.7.8 ,Adiusfmentof the record currenf ond the eleclronic

beqm indicotor circuits .

The electronicbeqm indicolors

The record current.

Adivstment of the osc, frequency ond the bios ..

Dislortion

Bolonce odiustment of lhe pre-omP ouiPuts

Adiusiment of the equolizoiion coils Ll ond L2 '.

Control of the recording curves .

Control of the ploybock curves .

Control of the lotol frequency resPonse

Power oulpul control .

Speed test

5.7

1.7

1.9

The flywheel with ihe copston

4.7,1 The broke for the flywheel

The speed chonge mechonism . . .

)O2l

5.7.9

5.7.

5.7

.tI

5.7.12

5.7.13

5.7.1

5.7.15

5.7.16

5.7.17

5.7.18

5.7.19

,1 i

.t t

5.8 Electricol

modificotionsintroduced

to the tope recorder

model

12 .....

...' 40

5,9 Modificolions

from four-trock

to iwo-frock

models.

.. ... 41

5.10 Modificofions

from 220volts50 c/sto ll0 volfs

60 c/s .. 4l

6.0 Portslist .'.....". 4l

6.0.1 Mechonicol

ports 4l

6.0.2 Elecrricolports ' . 46

1.0Technicalspecification,

Tandbergtape

recorder

models

12-4and12'2

Power

requirements: 220 volts50 c/s.

Power

consumption: 58watts

at2 X 1

,25

wattsoutputpower.

i 00 wattsaI2 X .l

0 wattsoutput power.

Motor: Four

pole.

Tapespeed: 71/2,33/t

and l7/einches

persecond.

The

amplifiersareequalized

to conform

with

NABstandards.

Playingtime: Four-trackrecordingson 1200ft.of tape:

Model

l2-4' Tapespeed

7Vzi.p.s.:Stereo

X 32 min.

Mono4

X 32min'

Tapespeed

37+i.p.s.:Stereo

2X 64min.Mono

4X 64min.

Tapespeed

l7/oi.p.s.'Stereo

2x 128min.Mono

4X i

min.

Model

l2-4: Two-trackrecordingson 1200ft.of tape:

Tapespeed

7t/zi.p.s.:

Stereo 32 min.

Mono

X 32 min. A

Tapespeed

3% i.p.s.:Stereo 64 min.Mono

X 64 min.

Tape

speed

17/6

i.p.s.:

Stereo

.l28

min.Mono2

X .I28

min.

Fastwind andrewind: Thefastwind or rewindof .l200

ft.of tape

takesapprox.

2 minutes.

Tape

path: Thetape moves

from left to right. The headsare positioned

with the air gaps

pointing

towards

thefrontof thetaperecorder.

Recordingtape: Maximum

reel

diameter

7". Good

qualityrecordingtape

isrecommended.

Automatic

slop: The

auiomatic

stopoperaies

during

record

or playback

aswell asduring

fast

wind

or rewind

modes.

Heads:

Modell2-4: Quarter-track

erase

head.

Quarter-track

combined

recordandplayback

head.Air gap: .003mm (.O012").

Model

I2-2: Half-trackerase

heao.

Half-trackcombinedrecord

andplayback

head.Air gap: .003mm (.00012').

Frequency

response: 7'

l, i.p.s.30-20.000c/s

('l 2 dB

40- 16.000c/s).

33/ai.p.s.30- I3.000

cls

(-r2 dB50- I

0.000

c/s).

17/ai.p.s.30- 2.000

c/s

(+2 dB

60- 5.000c/s).

lnAMPLIFIERoosition:t 2 dB30-.l6.000c/s.

Distortion: Thedistortionfromthe

record

amplifiers

isless

than

Thedistortionfromthe

playback

amplifiersis

lessthan

.5%. i

Signal

to noiseratio

Model

l2-4: Thesignal

to noiseratio

better

than

55 dBwhenthetapeis

recordedto optimum

recordinglevel,i.e.nearlyclosingof the electronic

beamindicator

(5% disloriion

fromthetape).

Model12-2' The

signal

io noiseratioisbetter

ihan

58 dBwhen

the

tapeis

recordedto optimum

recordinglevel,i.e.nearlyclosingof the electronic

beamindicator

% distortion

fromthetape).

Crosstalk: The

crosstalkreiection

better

than

dBat

400

c/s.

Wow and

flulter: Betterihan.I % at7t/z

i.p.s.tape

speed. I

Betterthan

.15%at

33/+i.p.s.

tapespeed.

Belterthan.25

al l'/o i.p.s.tape

speed.

Eraseand

biasfrequency:The

erase

andbiasfrequencyis85,5kcls.Theevenharmonicdistortion

in the bias

currentislessthan.5%.

Recording

levelindicaior' Theelectronicbeamindicatorsareequippedwith dampingcircuits.Theindicator

rangeis

25 dB,plus

overload.

The

indicatorsareclosing

atoptimumrecordinglevel

%distortion

fromthetape).

lnputs: 2 Microphone

inpu?s

(ch.

I and ch,2l:

lmpedance,200

ohmsunbalanced.Sensitivity:

l50pV. Dynamicrange *40d8.

Contacts:5 pinDINcontacts.

Oulputs:

Speakers,

Bass

control:

Treble

control:

Momentary

start/stop

tever:

Counter:

Tubes

models

l2-4

and

l2-2:

Transi

stors:

Rectif

iers:

Dimensions:

Weight:

2 line inputs

(ch.

I andch.

2):

HIGHLEVEL:

Impedance:I Mohm.

Sensitivity:

contacts

and DIN connector

marked

LOW

LEVEL:

mV. Dynamicrange+40 dB.

Contacts:Phono

CRPHONO

(pin

No.

3 and5).

lmpedance:

.l00

kohms.

Sensitivity:

7,5mV. Dynamic

range *40 dB. Contacts:

Phonocontactsand DIN

connector

markedRADIO

(pinNo. I and4).

FM-Multiplexinpuls:

Themodell2 taperecorderisfurnished

with a FM-Multiplex

switch

which

switches

themultiplexfilter

oroui.

The

switchcontrols

all

inputs.

PlaybackPreamplifier

oulpul:

lnternalimpedance

is5 kohms.Opencircuitoutputvoltage750 mV, independent

of the setting

of all switches

and controlsduring playback.

Two phonocontacts

(ch.

I and

ch.2) arefurnished

for connection

to external

poweramplifiers.

low lmpedance

oulpul:

Externalimpedance

is4 ohms.

Two standard

telephone

iacks

(ch.

I and ch.2) in

parallel

with two DINloudspeakercontacts

are

furnished

for connection

to external

loudspeakers.

Cenler

Channel

oulpul:

lmpedance

is 82 ohms from each amplifier. Output voltage in record posi-

tion is 75OmY open circuit.Output voltagein playback

positionand amplifier

position

(AMP)

is maximum3 volts

opencircuit.One standardtelephone

iack

parallel

with one DIN loudspeakercontact

arefurnishedfor connectionto head-

pnones.

Power

ouipul:

Maximumoutput

power

is I0 wattsin eachchannel.Twostandardtelephone

iacks

(ch.

I and ch.2) in parallelwith two DIN loudspeakercontactsare furnished

for

connectiontoexternal

speakers.

Twospeakers

7" X 4".

Thebassresponse

canbe continuously

increasedapprox.l2db at 80 c/s

during

playback

or in amplifiermode.This

increaseof the low frequencyamplification

will only be presented

on fhe channel

which issetfor playback

or amplification

evenwhen

the

other

channelisconnectedfor recording.

Thetreble

response

canbecontinuously

decreasedapprox.15 dBat I5 kc/sduring

playback

or in amplifier

mode.Minimum bassand maximum

treblecorrespondto

latfrequencyresponse.

The

momeniarystart/stop

lever

starts

or stops

the recording

or playback

instantly.

The4 digitcounter

shows

thenumber

of revolutionsof thetake-upturntable.

2 EAM86.

2 pairs

of complementarylransistors

AC 127,AC 128 (alternatively

AC 127,

AC r52).

2 pairs

of matchedtransistorsAD 150

(alternatively

AD 149

orSTF

213).

l0ea BC1098, 2 ea BC

114, 6 ea BC113, 2ea BC

1078, 2ea SE6002,

i ea

3030,

4 ea

284812.

Bridgerectifiers:

I ea

40 C

3200.

I ea B250 C 75/30 KP.

Inteakcabinetl5' I

long,I l" f

,u"

wide and67/u"high.

Approx.23 lbs.

2.0Thefunctionofthecontrols

l. Treblecontrol:

2. Basscontrol:

3. Volumecontrols:

4. Recordlevel

indicators:

Microphone

inputs:

Frontandrear

trimcovers:

Momentarystart/

stop

lever:

Functionselector

switch,channell:

,+1

Fig. l. The operoling conlrols.

Decreases

the treblecontinuously.Maximumtrebledecreaseis approx. l5 dB at

l5 kcis.The

treble

control

operative

during

playback

and

inAMP

position.

lncreasesthebasscontinuously.Maximum

bassincreaseisapproi. l2 dBat 80 c/s.

Thebassconirol

operative

during

playback

and

inAMP

position.

Conirols

the recording

gain in recordmode and the outputvolume in playback

mooe.

Upperknob:Channel

((Upper

track).

Lower

knob:

Channel2 (Lower

track).

lndicatesthe recordinglevel. Optimum recordinglevel is obtainedwhen the

electronicbeam

indicatorsarenearlyclosed.

Left indicator:Channeli (upper

track).

Right

indicator:

Channel2 (lower

track).

Low

impedance

inputs

(200

ohms)

channelI andchannel2.

Removethetrimcoverstocleanor demaqnetize

theheads.

Stopsthe recordingor playback

instantlywhen the lever is movedto the right

position.Therecord

or playback

will start

immediately

when the leveris moved

toleft

posiiion.

8. Activatestheelectroniccircuitsfor record,

playback

or amplifiermode,channell.

9. Funclionseleclor

switch

channel2:

'l0. Automatic

end

stop

switch:

Il. Speakerselector

switch.

12. Tapecounter:

13. Operatinglever:

14. Re-set

push

button:

; 15. Power

switch:

6. Speedselector:

Activates

theelectroniccircuitsfor record,

playback

or amplifiermode,channel

Stopsthemotorwhen

thetaperunsoutor if thetape

breaks.

EXT:Externalspeakersonly.

EXT* INT: External

and

internal

speakers.

INT:Internalspeakersonly.

CHI EXT,

CH2 INT:Theoutputfrom CHI is connectedto both external

speaker

terminals.Theoutput

from

CH2

connected

toboth

internal

speakers.

CH2 EXT,

CHI INT:Theoutputfrom CH2 is connected

to both external

speaker

terminals.

TheoutputfromCHI isconnectedto both

internal

speakers.

Indicates

the

position

of thetape.

Activates

the mechanism

in the lape recorderfor the different modesof operalion.

Re-setsthetape

counterfo zero.

Switches

themainsonoroff

Selectsthe requiredtape

speed.

3.0Theinput

and

outputterminals

The input and outpul terminals

togetherwith the

FM-MXfilter and the pre-amplifier

balance

adiust-

ment arelocated

at the rear

of the tape recorder

ref.

fiq.

2 and

MX-FILTER

SWITCH

cH.z cR cH.1

LOW PHONO RADIO LOW

Fig.

The

inputterminols

ond the FM-MX

filterswitcn.

PREAMP. BALANCE4 OHMS

OUTPUTCH.1 ADJ. SPKR.

CH.2

cH.1

HIGH

CH.2

HIGH HEAD. 4 OHMS

PHONES SPKR.

CENTERCH. CH.1

PREAMP. 4OHMS CENTER 4.

OHMS

OUTPUT

CH.2 SPKR

cH.2 CH. SPKR

cH.1

iqi

$;r{ii

:,1 i! I

Fig.3. The output terminols ond the bolonce odiustment.

MICROPHONE

INPUT5

The

modelseries

l2 is available

with two different

microphonecontacts.

TheEuropean

versionisfurnished

with DIN connec-

torsref

fig.4.

TheUS

version

isfurnished

with standard

telephone

iacks

ref.

fig.5.

Both versions

have the same specification:

Inpul

impedance

200 ohms unbalanced,

input sensitivity

150

trv.

Fig.4. Fig.5.

((.t '))

\t/cH2

VcHt 200

Mtc

4.0The

mechanism,

detailed

description

and

adiustment

instruction

Themain

functionof the

mechanical

systemis

todrive

theturntables

and the capstan

in the different modes of tape molion. Themechanical

function is activated

by theoperating

lever.

ass

Fig. 6. Top view, wilh lop cover removed.

4.I THE

OPERATING

LEVER

The

operatinglever(54.1)

hasfive positions

and is

located

atfhe right front cornerof the tape recorder:

Normalforward

drive,fast

forwarddrive,fastrewind,

free,andneutral.

The

operatingleveractivates

thefollowing

parts:

Themotor

switch

(33.2):

disconnectsthe power to the

motor (14.1)

in neutral

free position

of theoperating

lever,and activates

the elec-

tronicbeam

indicator

in nor-

malforward

drive,

whenthe

fape recorder

isset

to record

mode.

);Theeccentric

segment

(59.17)l guides the pressure

wheel

assembly

(5.l.3)

andthe lift-

ing arm

(59.i8).

activafes

the clutchesunder

both turntables

(65.1

, 65.2).

)

Thetrip bar

(52..I):

4.1.1 Themotorswitch

Themicroswitch

(33.2)

islocated

on the bracket

(54.9)

for theoperatinglever,

ref.fig. 7. The

switch

iscon-

nectedin series

with lhe motor

currentandisactivated

by theoperating

lever

(54.i)to shut

off the motorin

neutral

or free position.

The motor switch

also

dis-

iF connectsthe power to the electronic

beam indicafors

in neuiral

or freeposition

when thefunction

selector

switchesare setto record.

Adlustments

Theoperating

point

of the microswitch

(33.2)

should

besetaccording

tofi9.8.

Themotor

should

start

when

the operatinglever

(54..|)

is moved

from neutral

eithernormal

forward, fasl wind or fast rewind posi-

tion.Unscrew

the

three

screwsA, B,

andC ref.fig.7.

Adiustlhe horizonial

position

of the delrin bracket

(33.5) and ihe vertical position of the microswitch

(33.2)

obtaining

proper

positions

for correct

operating

poinl.

Fig.7, The operoling lever.

MICRO SWITCH

OPERATING POINTS

77^

/ z"\

77-

3'.)

---l>

OPERATINGLEVER

IHLL

Fig. 8. Adiusimeni of the operoting points for the microswitch.

4.1.2 The

eccenlricsegmenl

The

eccentric

segment

(59.17)

is located

underneath

theuppermounting

plate

(71.2),

and isconnected

the

operating

lever

(54.1).

Ref.

fig.9 and 10.

The eccentric

segment (59.17) moves the pressure

wheelassembly

(5.|.3)

with thepressure

wheel

l.l"

against

the capstan

(66.2)

when the operating

lever

(54.'l)

isbeingset

to normalforward

drive.

The

liftingarm (59..l8)

is linked

to theeccentricseg-

ment (59.17)

and releasesthe speed

transferwheel

(53.1)

from contacting

the moior pulley(62.1)

in all

operating

modes,except

in the normalforward drive

position.

Fig.9. The upper mounling plole, bollom view.

Adiustments

Adiustthereturn

sembly

(51.3)

by motion

of the pressure

wheel as-

bending

the lug (A) ref.

fig.9 to

ascertaineasy

threadingof the tape in the slot be-

tween the two trim covers (73.1

, 73.2). The tape

should

not

stick

againstthe

pressure

wheel

I.l

)dur-

ing

thethreading.

4.1.3 Thepressure

wheel assembly

The pressure

wheel assembly

(51.3)

is guided into

operating

position

by the eccentricsegment

(59.17)

when the operating

lever

(54.1)

is movedto normal

forwarddrive.

Thepressure

wheel

(51.1)

ismountedunderbalanced

springtension,with the pressure

wheel shaft

1.2)

runningthrough two oblong slots in the pressure

wheelbracket

(5LI2). This

mouniing

gives

the pres-

sure wheel (51.1) approx.6 mm (t/a") horizontal

springloaded

play,

aline

perpendicular

tothe

front

of the upper

mounting

plate

(71.2).

Ref.fig. 10.

Adiustments

The balanced

spring

tensionof the pressure

wheel

(51..|)

is adjusted

to obtain

uniform pressure

of the

pressure

wheel againstthe capstan.Loosenscrew E,

and

turn the spring

equalizationlatch

(51.1

l) clock-

wiseor counterclockwiseuntilthetape

runs

smooth-

ly by the pressure

wheel (5

l.i) in normal

forward

drive. Make surethat no air-pockets

are formed be-

tweenthe tape and the pressure

wheel (5

l.l) and

that

thetapeiscompletely

coveredby ihe rubbersur-

faceof thepressure

wheel.

Ref.fig. l0 and I1.

Fig. I0. The pressurewheel

ossembly, exploded view. tr --@

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