TANDBERG TCD 42OA User manual

TANDBERG'
TCD
42OA
CircuitDiagrams
with
AlignmentInstructions
n
TANDBERG'-The
European
Alternative

Electrical
checksand
adjustments
General
- 0 dB level is defined as:
0.775 V in the RADIO socket, using Ty'pe I or II
tapes.
1.2 V in the RADIO socket usingMetal tape.
1.5 V in the OUTPUT socketsusingType I or II
tapes.
2.3 V in the OUTPUT socketsusing Metal tape.
- Before adjusting, the tape path must be cleaned
and demagnetized.It is necessary
that the tape
path is correctly adjusted.
- Carry out the adjustments in the order described
because the adjustments affect each other.
- Remove the basepanel.
- When adjusting the Bias-traps
and the Bias-pre-
adjustment, the top panel must be removed.
Equipment required
- 2 millivoltmeters
- Audio signal
generator
- Frequency counter
- Distortion meter
- Wow and flutter meter
- Tandberg test cassettes:
- No. 21 (Speedcheck, 1000 Hz)
- No. 22 (Wow and flutter check, 3150 Hz)
- No. 23 (Azimuth adj. playb. head, 6300 Hz)
- No. 24 (Playback level adj., 1000 Hz)
- Measuringcassettes:
- Maxell UD XL I (Type I)
- Maxell UD XL II (Type II)
- Fuji Metal or TDK Metal MA (Metal)
Before adjusting, set buttons to:
- MPX-FILTER (situated at the back of the deck)
to OFF.
- Dolby NR.* to Off.
- Output Lcvel
controls
* The words "Dolby" isregistreredtrademarh of
Dolby Laboratories
Inc., US.Nfi stands
for
Noise
Reduction.
Before
adjusting,fold out page
5.
Oscillator
The oscillator
frequency
is between
80 and 100
kHz. The voltage
measured
on the erasehead
should
be
between6 and8volts
with TypeII or
Metal
cassettes.
Biastraps
- Remove the top panel.
- Nleasurewith a millivoltmeter on C107 and
C207 and adjust L101 and L201 to minimum
reading on the millivoltmeter.
Record/Playback head - azimuth
- Insert a Tandberg test cassette
No. 23 or a
standard azimuth cassette.
- Set the Monitor button to Taoe and connect a
millivoltmeter to eachchannel of the OTITPUT
sockets.
- Pressthe Play button. Adjust the playback
azimuth screw shown in the figure to obtain
maximum reading on eachchannel.
to maximum.
Playback
level
- Insert
Tandberg
test
cassette
No. 24 (Playback
level
adjustment
1000Hz).
- Adjust with the PLAYBACK LEVEL ADJ.
R317/R417
to 1.5V on the
OUTPUTsockets.
(In the RADIO socket,adjustto 775 mV.)
- If you useaDolby level
cassette,
adjust
to 1.2V
on the OUTPUT sockets
(0.615mV in the
RADIO socket).
Bias
(pre-adjustment)
- Set
theTCD 420Ato record,Metal
tape
loaded.
- Adjust with R21031IJ.2203
(Bias
Adjustment
Metal)
to approximately
8 - 9 mV measured
on
TPl andTP2 (on the Osc.
board),seefigure.

NOTE!
AdjustingtheTCD420A,usingthe RADlo-socket.
Overall frequency response with Metal tape
SettheTCD 420A to recording.
Adjust the gene-
rator to - 30 dB (= 25 mV on the millivoltmeters)
and record a40OHz, a 10 kHz, and a 15 kHz signal
at this level.
- Rewind and play back.
- Usethe 400 Hz signalas
a referenceand check
on both channelsthat the 10 kHz and 15 kHz
signals
arewithin the following tolerance:
r3dB.
If outside
thetolerance
adjust
R2103/R2203
BIAS
|DJ. M!,TAL. Then makea new recording,
play
backand
checkonce
more.
- If you cannot adjustto correctresponse
with
\?1991R2203, BIAS ADJ. METAL, thenadjust
R501/R601,
TREBLEADJ.METAL.
- Make
anewrecording,
playback
andcheck
once
more.
- Thencheckthe frequency
response
t 3 dB,30 -
18000
Hz.
- Whenthe frequency
response
is correct,
check
theresponse
with theDolby NR. circuit "On".
Recording Level - Metal tape
Connect anaudio-generator
and two millivoltmeters
to the RADIO-socket. Set the TCD 420A to
Record, use Metal tape. Adjust the generator to
400 Hz (= 450 mV on the millivoltmeters).
- Start recording.
- Rewind and play back (Output Level controls to
maximum).
- The millivoltmeters should now read approxi-
mately 450 mV (- 2 to 0 dB).
If outside the tolerance, make a new recording
while adjusting R105/R205, REC. LEVEL METAL
asrequired. Then play back and check once more.
Distortion - Metaltape
- Set
theTCD 420Ato recording.
- Generator
to 1000Hz (= 775mV on the
milli-
voltmeters).
- Rewindand
playback.
- Check
that thedistortionis( 3%.
- If outsidethe tolerance,
adjustR2103/R2203,
BIAS ADJ. METAL.
- Make
anewrecording,
playbackandcheck
once
more.
- Then check that the frequencyresponse
is
within thetolerance.
Signal/noise- Metaltape
Thesignal/noise
ratiosat 3To distortion
should
be
at least asgoodasspecified.Measure
with the
Dolby NR. circuit "On".
IECA-curve 68 dB
IEC Linear
RMS 56 dB
Program
meters
- Metaltape
- SettheTCD 420A to Record.
- Record a 400 Hz signalfrom the generator
(=11.2V on the millivoltmeters)
andadjust
the
program
meters
to 0 dB deflection
on theMetal
ry3l9_11th
Rl35/R235, METER LEVEL ADJ.
RECORD.
^

.*\ /
Adiustments
for typeI taPe
Recording Level
Adjustment
fortype ll tape
Recording Level
lf outsiderhe tolerance
(- 2 to 0 dB), adjust { gutsidethe tolerance,
- 2 to 0 dB, adjust
R529/R629,
REC.LEVEL I. Donot touctr
Rl05/ R104/R204,
REC.LEVEL II.
R205' REC' LEVEL METAL' - Make
anewrecording,
playbackand
check
once
- Make
anewrecording,
playback and
check
once more.
more.
- Usethe same
level as
for Metal tape (= 450 V on - Use the same
level as
for Metal tape (= 450 mV
the millivoltmeter). on the millivoltmeters).
- Record, rewind and play back. - Record, rewind and play back.
Overall frequency response Overallfreqeuncyresponse
Usethe same
levelas
for Metaltape
(= 25mV on
- Usethe same
level asfor Metal tape (= 25 mY the millivoltmeters).
on the millivoltmeters). If outsidethetolerance.
t 3 dB.
30- 18000
Hz,
If outside
thetolerance,
t 3dB,
30- 18000
Hz, adjust R21021R2202,
BIASADJ.
II.
adjust
R2101/R2201,
BIAS
ADJ.
I. - Then check the frequency response
with the
- Then check
the frequency
response
with the Dolby NR. circuit "On".
Dolby NR. circuit "On". Distortion
Distortion - Record 1000Hz at 0 dB (= 77b mV on the
- Record
1000
Hz at 0 dB (= 775
mV on the millivoltmeters)'
millivoltmeters). - Rewindand
playback.
- Rewind
and
playback. - Check
that the distortion
is( 2%.
- Checkthat thedistortionis42%. If outside
thetolerance,
adjust
R104/R204,REC.
If outside
thetolerance,
adjust
R529/R629,REC. LEVEL II and R2102/R2202 BIAS ADJ' II.
LEVEL I and
R21021F.2202,
BIAS ADJ. I. - Then check the frequencyresponse
and the
- Then check the frequencyresponseand the distortiononcemore.
distortiononce
more.
Speed
check
PlaybackTandberg
testcassette
No. 21 (Speed
check 1000Hz) andmeasure
with a frequency
counter.on
the
output:t 1%
(990
- 1010
onthe
counter).
If necessary,adjust
to correctspeedwith R208'
SPEED
ADJ. on theMotor controlboard.
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tcu|r
1727
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80 Part No.714136
Printed
inNorway
by Reclamo
A/S
GrTandbers
A/S,
1980
l:I Tandberg
A/S, Post
OfficeBox 55, Bogerud,N-Oslo
6, Norway