TANDBERG 3400X User manual

IffiEffi
SERVICE
MANUAL
SoooxD

CONTENTS
l.
l.l
r.2
,
2.1
99
3.
3.1
3.2
3.3
3.4
c.c
3.6
4.
4.1
4.2
4.3
4.4
4.5
5.
5.1
5.2
5.3
5.4
c.5
6.
6.1
6.2
6.3
6.4
6.5
7.
7.1
19
7.3
8.
8.1
8.2
8.3
8.4
9.
9.1
9.2
10.
11.
11.1
rt.2
11.3
Page
Introduction.... ..,....3
General ....3
Removingthetoppanel . ......3
Maintenance.... ...,.,.4
Cleaningthetapepath.. .......4
Lubrication .......4
Mechanicalchecksandadjustments.. .......5
Checking
the take-upforce andwinding force. . . . . . 5
Adjustingthetake-upforce. ....5
Adjustingthewindingforce. ...6
Adjustingthebrakes .....8
Rubberdrivebelt .......8
Pressurepadarm ...9
Tapepath ...10
Capstan .....10
Headparallelism. .......10
Tapeguideposts
and
guide
screws.
.. .. .. . . .11
Pinchroller .......11
Flutterroller. .....12
Head
alignment
with Tandberg test tapes,
four tracks . . . . .13
Playbackhead. ....13
Recordhead. .....13
Height
adjustmentby
trackmeasurement... ......13
Biashead ....I4
Erasehead ...I4
Headalignment
without Tandbergtest tapes,
four tracks . . . . . . .15
Playbackhead. ....15
Recordhead. .....15
Biashead ....15
Erasehead. .......15
Aligning the hum shieldfor the playback head. . . . .15
Headalignment,two
tracks .....16
Playbackhead. ...16
Recordhead. .....16
Erasehead ........17
Circuits .....77
Oscillator. . . .I7
Photoend-stop ........I7
Recordandplaybackfrequencyresponses . . .18
Faultinthetotalresponse
curve,onechannel..... ......19
Modifications... .......20
Changingthelinevoltageand
frequency... .......20
Changingfrom four tracksto two tracksversion . . . .20
Blockdiagrams ....20
Electricaladjustments.... .....22
Outputamplifiers
(3400X) .....22
Dolby*leveladjustments
(3600XD). .......22
Adjustments,allmodels.... ...23
Circuitdiagrams .... from page24
* Theword Dolby isa Trade
Mark of Dolby LaboratoriesInc., USA
-----.....-
-
t
a

1. INTRODUCTION
-
1.1 GENERAL
Only LH (Low Noise/HighOutput) tape shouldbe
used
for recording.Makesurethat the headsand
tapepath areclean.
To check
theheads:
-
l. Remove
the front head
coverby depressing
the
springloaded
buttonsatboth endsand
lifting
the coverstraightupwards.
2. Remove
thebackcover
by depressing
the spring
on its rearsideandlifting straightupwards.
When
electrical
adjustmentsareto be made,the
bottom panelmust
beremoved.
Thetapepathmust
bedegaussed
both beforeand
after adjustment.
Do not switch off the degausser
until it isabout 3 feet from the tapepath.
To makemagnetizedpartsof the tapevisible,
dip
the tapein "MagnaSee".Thisis a mixture of iron
oxide powder andalcohol.Iron oxide powder can
beobtainedfrom our service
department.
A
NOTE! All paragraphs
in this manualare
valid for:
Model3400X,from serialNo. 4300000
Model3500X,alldecks
Model3600XD,from serialNo. 4200000
1.2 REMOVINGTHE
TOP
PANEL
Remove
the headcoversandthe speedselector
knob. Then remove
the screws as
shownin Figure
1.1.
Removalof thetop panel will usually
only be
necessary
for checkingand adjustmentof clutches
andother partsin the drivemechanism.
Fi4.1.1. Toppanelscreu)s
.HHs..[n
-

2. MAINTENANCE
Fig.
2.1 Cleaning
the taPe
Path
2.1 CLEANING
THETAPE
PATH
It isimportant that the tapepath is cleanbefore
adjustments
aremade.If the heads
andguideposts
have
beenadjusted,
the tapepath must be de-
magnetized.
Cleaning
shouldbe carried
out with cotton-bud
sticks
(Q-tips)moistenedwith purealcohol
or
methylatedspirit. A special cleaning
kit called
"Tandberg ProfessionalTapeHeadCleaner"is
alsoavailable.
Aerosol
sprays
indentedfor videotaperecorders
maybeused,
but it isnot sufficient
just to spray
theparts;cotton-budsticks
mustalso
beused.
Obstinate
depositson guide
posts
shouldbe first
well softened
with the cleaning
agent
andthen
removed
with the aidof a toothpick.
ThepinchrollerA should
becleaned
if the tape
runsunevenlyor if thereare
visibledeposits
on
theroller (4 to 6 times
ayearshould
besufficient,
even
if the tape recorder
ismuch used).
Makesure
that the pinch roller is dry after cleaning.
2.2 LUBRICATION
NOTEIDo not usc
morethanone
dropof oilon
eachbearing,
asexcessive
oilmaypenetrate
into
thedrive
mechanism
and
disturb
friction
conditions.
The turntables,flywheel andtransferwheelare
mounted in selflubricating bearings
andshouldnot
need
attention under normal conditions. If for
some
reasonlubrication appearsto be necessary,
use
Teresso
oil No 43 or 47 from Esso.
The motor shouldbelubricated after every
3000hoursof operation.
Apply only one dropof
Teresso
oil No. 43 or 47 from Esso.
ffi --=
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t

A3.
3.2
3.1
MECHANICAL
CHECKS
AND
ADJUSTMENTS
CHECKING
THE
TAKE-UP
FORCE
AND
WINDING
FORCE
Fig. 3.1 Checking
the windingforce.
A 7" reel
with ahole
drilledin it 80 mm from the
hub holeisrequiredtogetherwith atorque gauge.
Insertthe legof the torque gauge
into the drilled
hole.The reelshouldbe allowedto rotate slowly
in the direction of the clutch torque while the
measurements
areperformed to obtain the speci-
fied
values.
see
table3.2.
ADJUSTING
THE
TAKE-UP
FORCE
Fig. 3.3 Adjusting the take-up
force.
NOTE! Do not touche the textile sideof the
belt with your fingers.
The rubber drivebelt doesnot moveduring normal
forward drive.This isbecause
atextile belt pro-
vides
the take-upforce viaadrivewheelmounted
behind the take-upturntable.
Adjust the take-upforce by movingthe spring,see
Figure
3.3.
If thewindingforce
isnot correct
it should
be
adjusted
as
explained
on thenext page.
]
Turntable Operating
lever
position Playback or
wind force
Rieht 25- 30
e*
Right >> 9o-2so
g*
Left 90-250
p*
Table
3.2 Clutch
torque
x It is
normal
for thewindingforce
to increase
20-30%
after
themachine
has
been
in conrinuous
operation
for sometime.
O

3.3 ADJUSTING
THE
WINDINGFORCE
f-x
!&t
..d5"
tl
U,
Adjusting the reelturntables.
Thewindingforceisdetermined
by the springs
A.
See
Figures3.5and3.7.If the tensionandthe
springsdo not change,the winding force is deter-
mined by the play on the reel turntable and the
clutchleaver.If thetension isstillnot correctafter
adjusting
the play, replace the spring
A.
Withthe
joystick in the FREEposition,
theplay
ontheturntableshould
bebetween0.5and1mm
as
shownin Figure3.4.Theplay on the left turn-
table
canbeadjusted
by turningthenut on the
turntable spindle.The play on the right turntable
canbeadjusted
by turningthe turntablepulley.
NOTE! If theturntablepulley (rightturntable)
must
beunscrewed from theturntable
it shouldbe
glued
into positionaftertheplayhas
beenadjusted.
Fig,
3.4 Checking
the
play on theturntables
!
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vd
A\
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w
A
W -L-r--,\- \\
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nWZ
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d\?=,^
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Thesupply turntable
fil
Fig. 3.5

-
Fig.
3.6 Checkingthe
play on theclutchleaers
Adjustingthe clutch lever.
With
the
joystickin the NEUTRAL (middle)
position,
theplayon the clutch
levers,rightand
left,shouldbebetween
0.5and1mm.
To adjust
this
play,
turn the screws
B shown in
Figure
3.6.
When
the play on the turntable andthe clutch
levers
has
beenadjusted,
the winding forces
will
be
correct.Check
these
forces
with theaidof the
table
onpage 5.Adjusting
thebrakes- see next
page.
w
A
K -t^]- A)
^W
d ^r7?
d\FEE
€
4€e\
A
(ffi)
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B
a
Fig.
3.7 Thetake-up
turntable

3.4 ADJUSTINGTHE
BRAKES
This adjustment procedure
turntables, but referende is
table.See Figure3.8.
isthe samefor both
made to the right turn-
Set
thejoystick to the ) position. Check that the
clearance
between the brake pad and the turntable
is I mm (0.4") approx. If necessary adjust screw D.
Set the joystick to ( , alternatively D and
check the clearance.
3.5 RUBBERDRIVE
BELT
The rubber drive belt doesnot move in PLAY
mode. This is becausea textile belt provides
the take-up force via a drive rvheelmounted
behind the take-up turntable.
When changingthe drive belt, make surethat the
new belt sitscorrectly on the motor pulley as
shown in Figure3.9. The belt must sit in the top
two belt grooves
and not in the samegroove.
Thebelt must not crosson the wrons side
of the
pulley.
Fig.3.8. ,ldjustirtg the brakeson the right tunttable
<\
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=it
Fig.3.9 Replacingthe driuebelt
T

.A\
;\
a
Thelifting arms
for the drivebelt shouldbe
adjusted
whenthe
joystick isin NEUTRAL (nrid-
position).
Adjust for I mm clearancewith flat
pliers
asshownin Figure 3.10.Adjust A first and
theB.
3.6 PRESSURE PADARM
Withthe
joystick in the ) position,
the tension
from thepressure
padarmagainstthebracket
should
be
between80 and100 g.Thispressure
should
bemeasured
as
shown
in Figure
3.11.
Adjustby bendingspringA which presses
the
pressure
padarm
againstthehead. Checkthat the
pressure
pad
arm
isparallel whenit meets
the
bracket.
Fi9.3.10.
Adjustingtheclearanceon the driuebelt
Fig.3.
1
1.lvleasuring
the
pressure-pressure

4. TAPE
PATH
4.1 CAPSTAN
Before the heads
and tape guide posts are adjusted,
the position of the capstanmust be checked.
Useipecial tool No. 5 asshown in Figure 4.1. All
three legsof the special
tool should rest on the
upper mounting plate. If one or more of the legs
dois not rest on the plate' the capstanneeds
adjusting.To adjust the capstan,
loosen the three
coioured screws and adjust the capstan until all
three legsof the tool rest on the plate. Tighten up
the screws and check again that the legsare all
touching the Plate.
NOTE! The capstan
will not go out of adjustment
with normal use and transit.
4.2 HEAD
PARALLELISM
Check that the heads are parallel with the aid of a
tape path gauge'
seeFigure 4'2. This adjustment
aflects the passage
of the tape through the tape
path, and where the headsareseriously out of
ilignment the complete tape path must be checked,
see
next page.
Fig.4.1.
Actjusting
thecapstan
with special
tool No'5'
4N
1
s
Adjust
Forwards Adjust
Backwards
r-TIl
L__J
Correct
Zenith
Fig.4.2.
Adjustirtg
with thetape
pathgauge'
(s'

4.3 TAPE
GUIDE
POSTS
AND
GUTDE
SCREWS
4.4 PINCH
ROLLER
Fig. 4.3.Adjustable tape
guide
posts.
a
;\ Thread a tape into the tape path. pull the joustick
slowly down into the ) position and tishten the
tape by rotating the left reel slowly cloikwise.
Check that the tape doesnot come into contact
with the edges
of the tape guide screws.
If necessarv,
adjust the guide screws
shown in Figure 4.3.
When the machine isin the playback mode and
tape ispassing
the heads,
the tape may touch the
top edges
of the guide posts and guide screws,
but
under no circumstances
should it twist or distort.
The two adjustments possible
on the pinch roller
areparallelismand azimuth.
Parallelism.
Pushthe pressure
roller arm in and check that the
pinch roller is parallelwith the capstan.
To adjust,
loosenscrewA and adjust screw B (Figure 4.4)
until the pinch roller and capstanare parallel.
Tighten up screwA.
Azimuth.
Put a tape into the tape path and move the joystick
to ) . Check that the tape doesnot distort when
it has
passed
the pinch rbller. To adjust, loosen
screwA and move bracket C (Figure 4.4) until the
tape runs properly. Tighten up screw A.
Fig.
4.4.Adjusting the
pinch roller.
A
ttr

4.5 FLUTTER
ROLLER
Parallelism.
Loosen
screwA (Figure 4.5).
Insert
ascrewdriver
into the slot and movethe upperbearingforwards
or backwards until the flutter roller isparallel
with
theheadfront.
Azimuth.
Setthespeedselector
to 7Vzips,
put atapeinto
thetape
path,
andmove
the
joystick to ) . Insert
ascrewdriverasshownin Figure4.6andtwist it
to move
the flutterrollerto theleft until thetape
just touchesthetop edge
of thenearest tapeguide
post.
Move the screwdriver to the position shown in
Figure 4.7 and move the flutter roller carefully
to the right. If the roller is correctly adjusted the
tape will lift slowly upwards from the bottom part
of the tape guide post and touch the upper part
of the tape guide post without curling.
This adjustment can be checked with a lamp placed
behind the tape path. Look from the front to see
light between the tape and the lower part of the
tape guide post.
Fig. 4.5.Adjusting theparallelisem of theflutter roller.
Fig. 4.6.Adjusting the azimuth of theflutter roller.
(R
,----l
17/
IE
Fig. 4.7.Adjusting the azimuth of the
flutter roller. ($

I
5. HEAD
ALIGNMENTWITH
TANDBERG
TESTTAPES,
FOUR
TRACK
NOTE!
The tape path must be thoroughlv cleanedbefore
adjustments arecarried out. Usetape without any
defects.If the headshavegrooves
causedby wear,
adjustment of the heads
should be avoided.
Sealall screws in the tape path after the adjust-
ments havebeen made.
After replacement of a single part in the tape path,
it may often be necessaryto adjust the new part
only. If, however, more parts haveto be adjusted,
a complete check and adjustment of the entire tape
path must be performed. Adjustments must be
carried out in the samesequence
as
explained in
this section.
5.1 PLAYBACK
HEAD
Connect an a.c.voltmeter to eachof the LINE
OUT socketsand set the SOURCE/TAPE buttons
to TAPE.
Height adjustments
Playback test tape No. 1. This is a full track pre-
recorded tape with 1,000 Hz recorded at 7/z ips
and with the area
corresponding to track 3 reduced
by approximately 35 dB. Adjust the height of the
pla,vback
head
by means of scrcwA, Figr-rre 10.1,
page
2l until minimum outplrt is obtained from
track 3, channel R while maintaining the head-front
parallelto the tapc.
Azimuth adjustments
Playback Tandberg test tape No. 2 at 7tl:ips (or
a standardazimuth tape). Adjr,rst
the azimuth posi-
tion of the playback head by meansof screw B,
Figure
10.1 (page
2l) until maximum output on
the voltmeters is obtained on both channels,
or
adjust for the best compromise.
5.2 RECORDHEAD
Height adjustment by visualinspection
Insert a new tape and setthe deck to normal
forward drive ( ) ). Check visually that the tape
appearsto run parallel with the upper track on
the record
head,
n,ithin approximately 0.1 mm
(0.04") seeFigure5.1. If necessaryadjustthe
height with scrervsC, Figure 10.1, rvhile main-
taining the head-front parallel with the tape.
Height LateralAlignment
t;
^
a\
J^-
"Qf
l--r
t
v
^
l
l
(
Azimuth Zenith
5.3 HEIGHT ADJUSTMENTBYTRACK
MEASUREMENT
Record in stereo a 1,000 Hz siqnallvell above
the
normal level,first in one direction, then in the
oppositedire ction. Cut off alength of tape and
dip into a solution of fine-grainediron-oxide
powder and alcohol (MagnaSee).
The tracks will
then be visible asfour dark stripes.Figure 10.2
(page
21) sholvs
the correct pattern on the tape
and the patterns
obtained when the headiseither
too high or too low. If necessary,
adjustthe
height of the head and repeat the measurement
until the patters are correct.
Azimuth adjustment
Load the dcck rvith a new tape and record at
33/a,tpsa 12 to 13 kHz signalin stereo.Set the
SOURCE/TAPE buttons to TAPE. Adjust both
INPUT LEVEL potentiometers for approximately
150 mV readingon a.c.voltmetersconnected
to
the LINE OUT sockets.Adjust the screw D
(figure 10.1) for maximum output from both
channels,
or the bestcompromise.
Approx.0.1 mm of upper
polepiece
visible
above
tape.
-
Fig. 5.1. Four track record head. t'Et

/
5.4 BIAS
HEAD
Vertical adjustment
Move the operating leverslowly to the normal for-
ward drive position ( I ) and check that the head-
front of biasand record headsareparallel. If
necessary,bend the arm of the biashead asrequired.
Height adjustment
Setthe deck to the stereo
screw the locking screwH
turn.
record mode, and un-
(Figure 10.1) about one
,({\ 1
Connect an a.c.voltmeter acrosseachhalf of the
record head. Nlove
the bias head up or down by
means
of adjustment screwM (Figure 10.1) for
the highestpossible
reading on the voltmeter.
Check that the tape runs freely in the groove in
front of the biashead, and that there is sufficient
clearancebetween the bias head and the mounting
plate for the record head. If necessary,
raisethe
biashead slightly. The height position of the bias
head isnot critical. Before tightening screw H,
carry out the horizontal adjustment asfollows.
Horizontal adjustment
Connect
an a.c. voltmeter acrosseachhalf of the
record head and setthe deck to the stereorecord
mode. Insert a screwdriver in the groove shown in
Figure 5.2 and tilt the biashead to the right. Then
tilt the biashead carefully by meansof the screw-
driver towards the left until the induced voltage
(bias)
in the record head increases
to a maximum.
Continue tilting the head towards the left until
the induced voltage (bias)in the record head is
redr.rcedto between 10 and lSYobelow maximum.
Tighten screw H while maintaining the correct
horizontal position for the head. Then re-check the
output voltage.If the voltage haschangednotice-
able,the horizontal adjustment procedure must
be repeated.
Fig.5.2. Ilorizontal adjustment for the bias
head.
5.5 ERASEHEAD
Height adjustment
By visualinspection, check that approximately
0.25 mm (0.01") of the upper half of the erase
head is visible above the tape, seeFigure 5.3. Insert
'fandberg test tape No. 9 and record on channel R
a 400 Hz signalwell abovenormal recording level.
Dip the tape in a solution of fine-grainediron-oxide
powder and alcohol (NtlagnaSee).Check that the
recorded track is positioned in the centre of the
erased
track, see
Figure 10.3,page
21.
Approx. 0.25 mm of
upper
ferrite
core
visible
abovetape.
{(\
l- s )-==-
\i._,-===-
//\
Vrl
,V/ \
Fig. 5.3. Four trech erasehead.

G,
A
a\
6.
6.1
HEAD
ALIGNMENT
WITHOUT
TANDBERGTESTTAPES,
FOUR
TRACK
PLAYBACK
HEA,D
Height adjustment
Adjust the height of the playback head by meansof
the screwsA, Figure 10.1,page
21. The upper edge
of the tape shall run flush with the upper part of
the head lamination for channel L. SeeFisure 6.1.
Azimuth adjustment
Setthe SOURCE/TAPE
buttonsto TAPE. Play
backastandardazimuthalignment
tape
with an
a.c.
voltmeter
connected
to each LINE OUT socket.
Adjusttheposition
of theplayback
head
by the
azimuth
adjr.rstment
screw
B, Figure 10.1until a
maximum
readingisobtainedon the voltmeters.
6.2 RECORD
HEAD
Follow the instructions givenin Paragraph5.3.
6.3 BIAS HEAD
Follow the instructions givenin Paragraph
5.4.
6.4 ERASEHEAD
Height adjustments
Adjust the height of the erasehead by meansof
the screwsK and L, see Figure 10.1.
Approximately 0.25 mm (0,01")of the ferrite
core for the upper track of the erasehead should
be visibleabove the tape, see
Figure 6.2.
Upper edgeof tape
coincideswith upper
edge
of upper
pole
piece.
Fi7.6.1.
Four
track
playback
head.
6.5.ALIGNINGTHE
HUM
SHIELD
FOR
THE
PLAYBACKHEAD.
The hum shield for the nlavback head is oositioned
on the pinch roller arm to inut the shield is right in
front of the head during plal,back. Set the deck to
stereoplayback with both SOURCE/TAPE buttons
in the position TAPE without tape in the tape path.
Put a piece of paper between the photoelectric end-
stopsensor
and the light. Set the deck to PLAY.
Connect an a.c.voltmeter to eachof the LINE
outDuts. Hold the shield and loosen screwE
(
t lgure l U.
I ) one quarter turn.
Pull the shield as far away from the head as
the
mounting hole permits. Ad.justthe shield sideways
to obtain a minimum readingon both voltmeters,
or best possible compromisel When adjustment
iscompleted, tighten the screwand sealwith
lacouer.
Approx. 0.25 mm of
upperferritecorevisible
abovetape.
I;
F-ig.
6.2. Four track erase
head.

7. HEADALIGNMENT,
2TRACKS
7.1 PLAYBACK HEAD
Height adjustment
Adjust the height of the playback headby means
of the screws A, Figure 10.1.The tape shall
run
parallelwith the upper and lower edgesof the
laminations
of the plal'back head, see
Figure 7.1.
If necessary,re-adjustirnd check the azimuth
position.
7.2 RECORD HEAD
Upper
and lower
edge
of tape
coincidewith
upper
and lower pole
pieces,
Fig. 7.1. -fu'o track playback ltcacl.
Ferrite
coresvisible
above
andbelowtape.
,
4$
I
I
1
{$\
Height adjustment
Adjust the height of the record
the screwsC, Figure 10.1. headby n-reansof
Record on channel L a 1,000 Hz signalat 7Yzips
well abovenormal recording level, first in one
direction, then in the opposite direction. Cut off a
lenth of the recordedtape
and dip it into a solu-
tion of fine grainediron-oxide porvder and
alcohol (N{agna See).Check that the tracks are
distributed symmetrically across
the tape. See
Figure 10.4,page
21. I{ necessary,re-adjustand
check the azimuth nosition.
7.3 ERASEHEAD
Height adjustment
Adjust the height of the erase
headby meansof
the screws
K and L, Figure 10.1.
Adjust until equal parts of the ferrite core
s
arevisible aboveand belor.t'the tape, seeFigure 7.2.
1
((R
1
Fig. 7.2. Tu,o track erasehead. (s

CIRCUITS
8.2 PHOTO
END-STOP
8.1 OSCILLATOR
fhe oscillatorfrequency is g5.b klfz for a stereo
recording. N.{easure
this frequency rvith a frequenc_v
counter on the biashead and acljust
r,vith
C502 on
the oscillator
board.
8.
;\
0
I
ra
8.1.1 Erase
voltage
Prepare
the machine for a stereorecording.
Connect a VVN{ to the upper half of the erase
head
via a lowcapacity^p^robe.-Check
that the voltage is
between
80 and 120 V. Check rhat the ,u*. r.iltog.
appears
across
the bottom half of the head. Set thl
machine to record on channel L, ancl
check that
the voltageis the same
on the upper half of the
head. The permissable
difference^betweenthe
voltages
on the two halves
of the head from a
stereorecording is l0 V max. Carry out the same
check for channel R.
8.1.2 Bias
current,pre-adjustment
Prepare
the machine for a stereorecording, ancl
use
a VVX{ to measure
the voltage across
ih. r.,pp.,
half of the biashead.Adjust the"voltas
e to 22 y
by means
of R401. Che& rhat the uoliage
across
the bottom half of the head
is 22 V andidjust
by means
of R400.
Demagnetize the heads
and tape path.
*{F:rl- E .;.r Og
r r oH tFE* o:
I I I _ffiFqos
liri) I ad6-
nlt I
5;
-e'
VE":
!J -ft5,.F
l?tr,36-
? rt---h '*/ 5 .- -
J ${ .tilo;
I I q@r Lql
IHt oq
T so ?t- os
l-_ . rm
zto
r--rl(*De
df:t r JEini-L
r# r8fr,*s
--H m,rnSj;T,l9rT[qt!H
dRsoTh
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.---- Mltr a !fi.d8jh5ft
@s ffi I lo's=tF?ql
- X" | ?., , r
r6{H
t T€ I I I
f_-3 lH t"_LJ
9RsloF a o
I - n€ t*^'-l
t_Etpgf r I
I +F"
L-
L
_.1
r
Fig. 8.1. Osctllator boartl.
]3,chanSe the lamp, take the screrv
out of the tape
gulde post, pr-rsh
the photo end_stop
unit back, and
lift it up. See
Figureg.2.
Th.e
sensitivity of the photo end_stop
can be
adjusted
by means
of nSlZ on the oscillatorboard.
See
Figure8.1.
G, Fig. 8.2. Photo ent!stop.

8.3 RECORDAND
PLAYBACK
FREOUENCY
RESPONSES
8.3.f Recordarnplifier
Connect a 100 ohm resistorin serieswith the record
headand earth asshown in Figure 8.3. Connect an
audio oscillator to the LINE input of eachchannel
and a VVN{ across
the 100 ohm resistor.Short
circuit the trimming capacitor C502 in the tape
recorder oscillator. Put the machine into the stereo
record mode. Set the record level to - 30 dB on
the meter (30 dB below normal). This 30 dB
attenuation should be obtained asfollows:
l0 dB with the INPUT LEVEL knobs on the
machine and 20 dB with the output control on the
audio oscillator.
Tune the audio oscillator to 400 Hz and usethis
for the referencelevel on the VVN{ (0 dB).
Sweep
the audio oscillator over the frequency
rangeand check that the readings
on the VVN{
correspond to the curvesshown in Figure 8.4.
8.3.2 Playback amplifier
Connect a22 ohn resistorin series
with the write
lead on the playback head. Connect an audio
oscillator
in series
with a 1 k ohm resistor
and a
100pF capacitoras
shown in Figtrre
8.5. Connect
a VVN{ to the outputs of channelsL and R, and
setthe outDut selectorto STEREO.
Use an WM to check the shape
of the playback
frequency curve.Tune the audio oscillator to 400
Hz and adjust the signal level to 75 mV measured
on the LINE OUT sockets. Check that the fre-
quency responcecuryesagreewith Figure 8.6.
Fig. 8.3. Measuring the recording response.
50 100 200 500 1t 2k
(F
fl.t f,
Fig. 8.4.Recordingresponse
curues.
5k rq 2()k
AMPLIFIER
{N
Fig.8.5.
Measuring
theplayback
response.
I'ig. 8.6. Playback response cuTves. o,(

8.4 FAULT INTHETOTAL
RESPONSE
CURVE,
ONECHANNEL
l;
^
/rl\
Play back test tape No. 3
to check the playback correction
curve.
lsthe playback correction curvecorrect?
YES
Setthe machineto
record.
Connectan audio
oscillatorto the LINE input andapply
the frequenciesshown in Figure8.4.
Check that both the meters
on
the machine
follow the
curve
in Figure8.4
Fault in the record heador the bias head.
Change
over
the wiring on
thetapehalvesof the playback head.
Play
back No. 3 testtapeagain.
lsthe fault on the samechannel?
Fault in the playback
correctioncircuit.
Fault in the recordcorrectioncircuit
Fault in the playback
head.
NO
NO
NO
\,^
x
/
IlEt
F

9.0 MODIF
ICATIONS
9.1 CHANGINGTHE
LINE
VOLTAGE
AND
FREOUENCY
A label on the motor showsyou how to wire the
transformer and motor for a different line voltase
and frequency.
When modifying from 50 Hz to 60 Hz, or vice
versa,
the motor pulley hasto be changed.
Motor pulley for 50 Hz, orderingNo. 243940C
Motor pulley for 60 Hz, orderingNo. 273787
10. BLOCK
DIAGRAMS
9.2 CHANGING
FROMFOUR-TRACK
TO
TWO.TRACK
VERSION
'fhe following parts must be changed
when
a four-track versionis modified to a trvo-track
version and when new heads
are fitted.
The value of the total capacitance
islabelled on the
heads.
Part Four track Two track
Record head
Playback head
Erase
head
Biashead
Rl36
R236
c400
c401
c402
c403
F53-11R
c03-l0P
D84-1lE
2079-03B
3.9k ohms
3.9k ohms
3300pF*
3300
pF*
250
pF*
250
pFx
F82-07R
FB3.11P
D87-20E
2958-04B
2.7
k ohms
2.7
k ohms
3300pFx
3300
pF*
250
pFx
250
pF*
fi\
x Capacitor must be conuected in parallel until
value of total capacistance
is achieved.
I
,(R
e--{
230V50
Hz
115V
50Hz
130V50Hz
BLOCKDIAGRAM
TB
34OOX ir\ rl