Sony hcd-tb20, Service Manual

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25
HCD-TB20
Record Level Adjustment
Procedure:
INTRODUCTION
When set to the test mode performed in
Tape Speed Adjustment ,
when the tape is rewound after recording, the “REC memory mode”
which rewinds only the recorded portion and playback is set.
This “REC memory mode” is convenient for performing this
adjustment. During recording, the input signal FUNCTION will
automatically switch to MD.
(After recording, turn the
m/M knob without stopping will
return to the position where recording was started.)
1. Press FUNCTION button to select MD. (This step is not
necessary if the above test mode has already been set.)
2. Insert a tape into deck, press the REC PAUSE/START button,
and then press the
Y button to start recording.
3. Mode: Record
4. Mode: Playback
5. Confirm playback the signal recorded in step 2 become
adjustment level as follows.
If these levels do not satisfy adjustment level, adjust the RV652
(L-CH) and RV602 (R-CH) on the TC board to repeat steps 3
and 4.
Adjustment level:
CN322 playback level: 47.2 to 53.0 mV (–24.3 to –23.3 dB)
AF OSC
MD IN
315Hz 50 mV (–23.8 dB)
blank tape
CS-123
set
attenuator
600
Ω
recorded
position
level meter
set
MAIN board
CN322
Pin
5
or TP42 (L-CH)
Pin
9
or TP46 (R-ch)
CD SECTION
Note :
1. CD Block is basically designed to operate without adjustment.
Therefore, check each item in order given.
2. Use YEDS-18 (3-702-101-01) unless otherwise indicated.
3. Use an oscilloscope with more than 10M
Ω
impedance.
4. Clean the object lens by an applicator with neutral detergent
when the signal level is low than specified value with the
following checks.
S-Curve Check
Procedure :
1. Connect an oscilloscope to TP (FE1).
2. Connect between IC103 Pin
qj
TP (FEI) and TP (DVC) (1.65 V)
by lead wire.
3. Turn the power on.
4. Load a disc (YEDS-18) and actuate the focus search. (In
consequence of open and close the disc tray, actuate the focus
search)
5. Confirm that the oscilloscope waveform (S-curve) is
symmetrical between A and B. And confirm peak to peak level
within 2 ± 0.5 Vp-p.
6. After check, remove the lead wire connected in step 2.
Note :
• Try to measure several times to make sure than the ratio
of A : B or B : A is more than 10 : 7.
• Take sweep time as long as possible and light up the
brightness to obtain best waveform.
RF Level Check
Procedure :
1. Connect an oscilloscope CH1 to TP (RFDC) and CH2 to TP
(RFAC).
2. Turn Power switch on.
3. Load a disc (YEDS-18) and playback the number five track.
4. Confirm that oscilloscope waveform is clear and check if RF
signal level is correct or not.
BD board
oscilloscope
TP(FE1)
TP(DVC)
symmetry
S-curve waveform
within 2
±
0.5Vp-p
A
B
TP(RFDC)
BD board
oscilloscope
TP(DVC)
TP(RFAC)
TP(DVC)
CH1 CH2