TANDBERG'
TCD
42OA
CircuitDiagrams
with
Alignment Instructions
n
TANDBERG'-
The
European
Alternative
Electrical
checks and
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 using Metal
tape.
1.5 V in
the OUTPUT
sockets using Type I or II
tapes.
2.3 V in the OUTPUT
sockets
using
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 base panel.
-
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
(Speed check,
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)
- Measuring
cassettes:
- 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"
is registrered trade marh
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 erase head
should
be
between 6
and 8
volts
with Type
II or
Metal
cassettes.
Bias traps
-
Remove
the
top
panel.
-
Nleasure
with 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 each channel
of the OTITPUT
sockets.
- Press
the
Play
button. Adjust
the
playback
azimuth
screw
shown in the figure
to obtain
maximum reading
on each channel.
to
maximum.
Playback
level
- Insert
Tandberg
test
cassette
No.
24
(Playback
level
adjustment
1000 Hz).
-
Adjust
with the
PLAYBACK
LEVEL ADJ.
R317/R417
to
1.5 V
on the
OUTPUT sockets.
(In
the
RADIO
socket, adjust
to
775
mV.)
- If
you
use a Dolby
level
cassette,
adjust
to
1.2 V
on
the
OUTPUT
sockets
(0.615
mV in the
RADIO
socket).
Bias
(pre-adjustment)
-
Set
the
TCD
420A
to record, Metal
tape
loaded.
-
Adjust
with
R21031IJ.2203
(Bias
Adjustment
Metal)
to
approximately
8 - 9 mV
measured
on
TPl and
TP2 (on
the
Osc.
board),
see figure.
NOTE!
Adjusting the TCD
420A, using the
RADlo-socket.
Overall
frequency
response
with
Metal
tape
Set
theTCD
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.
-
Use the
400
Hz
signal as
a reference
and check
on both
channels
that the
10 kHz
and 15 kHz
signals
are within
the
following
tolerance:
r3dB.
If
outside
the tolerance
adjust
R2103/R2203
BIAS
|DJ.
M!,TAL.
Then
make
a
new recording,
play
back and
check once
more.
- If you
can not
adjust to
correct response
with
\?1991R2203,
BIAS ADJ.
METAL,
then
adjust
R501/R601,
TREBLE
ADJ. METAL.
-
Make
a new recording,
play
back
and check
once
more.
- Then
check the
frequency
response
t
3 dB,
30
-
18000
Hz.
-
When
the
frequency
response
is
correct,
check
the response
with
the
Dolby
NR.
circuit
"On".
Recording
Level
-
Metal
tape
Connect
an
audio-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
as required.
Then
play back and check
once more.
Distortion
- Metal
tape
-
Set
the TCD
420A
to recording.
- Generator
to 1000 Hz
(=
775 mV on the
milli-
voltmeters).
-
Rewind
and
play
back.
-
Check
that the distortion
is
(
3%.
- If
outside the
tolerance,
adjust R2103/R2203,
BIAS
ADJ.
METAL.
- Make
a new recording,
play
back
and check
once
more.
-
Then
check
that
the
frequency
response
is
within
the
tolerance.
Signal/noise -
Metal tape
The signal/noise
ratios at
3To
distortion
should
be
at
least
as good
as specified. Measure
with
the
Dolby
NR.
circuit
"On".
IEC
A-curve
68
dB
IEC Linear
RMS
56
dB
Program
meters
-
Metal
tape
-
Set the TCD
420A
to Record.
-
Record
a
400
Hz
signal from the generator
(=11.2 V
on
the millivoltmeters)
and adjust
the
program
meters
to 0 dB deflection
on
the Metal
ry3l9 _11th
Rl35/R235,
METER
LEVEL
ADJ.
RECORD.
^
.*\
/
Adiustments
for
type
I taPe
Recording
Level
Adjustment
for
type
ll tape
Recording
Level
lf outside rhe
tolerance
(- 2 to 0
dB),
adjust
{
gutside
the tolerance,
-
2
to 0
dB,
adjust
R529/R629,
REC. LEVEL
I. Do
not
touctr
Rl05/
R104/R204,
REC. LEVEL
II.
R205'
REC'
LEVEL
METAL'
-
Make a new recording,
play
back and
check
once
- Make a new
recording,
play
back
and
check
once
more.
more.
-
Use
the
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
Overall
freqeuncy
response
Use the same
level as
for Metal tape
(=
25
mV on
-
Use
the
same
level
as for
Metal tape
(=
25
mY
the millivoltmeters).
on the millivoltmeters).
If
outside the tolerance.
t
3 dB.
30
-
18000
Hz,
If outside
the tolerance,
t
3 dB,
30
- 18000
Hz,
adjust
R21021R2202,
BIAS ADJ.
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
1000
Hz
at 0 dB
(=
77b mV
on
the
- Record
1000
Hz at 0 dB
(=
775
mV
on
the
millivoltmeters)'
millivoltmeters).
- Rewind and
play back.
- Rewind
and
play back.
-
Check
that the distortion
is
(
2%.
- Check that
the distortion
is
42%.
If outside
the tolerance,
adjust
R104/R204,
REC.
If outside
the tolerance,
adjust
R529/R629,
REC. LEVEL
II and
R2102/R2202
BIAS ADJ'
II.
LEVEL I and
R21021F.2202,
BIAS
ADJ.
I.
- Then
check
the
frequency
response
and the
- Then
check
the
frequency
response and
the
distortion
once more.
distortion once
more.
Speed
check
Play
back
Tandberg
test cassette
No.
21
(Speed
check
1000
Hz)
and
measure
with a
frequency
counter.on
the
output:
t
1%
(990
-
1010
on the
counter).
If necessary, adjust
to correct
speed with
R208'
SPEED
ADJ. on the
Motor
control
board.
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