DOWNLOAD Sony CHC-TB10 / CHC-TB20 / HCD-TB20 Service Manual ↓ Size: 12.26 MB | Pages: 70 in PDF or view online for FREE

25

INTRODUCTION
When set to the test mode performed in 

,

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)

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.

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.

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

26

Note: Clear RF signal waveform means that the shape “ ‡ ” can be

clearly distinguished at the center of the waveform.

Procedure :
1. Connect an oscilloscope to TP (TE1) and TP (DVC).
2. Turn the power on.
3. Load a disc (YEDS-18) and playback the number nine track.
4. Press the  BX  button. (Becomes the 1 track jump mode.)
5. Confirm that the level B and A (DC voltage) on the oscilloscope

waveform.

6. Adjust RV101 on the BD board so that the center of waveform

becomes the same voltage of DVC. (i.e.  A=0V)

[BD BOARD] (Conductor Side)

RF signal waveform

VOLT/DIV : 200mV
TIME/DIV : 500ns

level : 0.65 

±

0.15Vp-p (RFDC)

1.1 

±

0.4Vp-p (RFAC)

TP(TE1)
TP(DVC)

BD board

oscilloscope

level=1.0 

±

0.5Vp-p

symmetry

A (DC voltage)

center of
waveform

B

DVC

1 track jump waveform

TP (TE1)

TP

(RFAC)

TP

(RFDC)

TP (FE1)

IC101

IC103

RV101

TP (DVC)

1

15

30

1

20

21

40

60

80

41

61

16

TP

(FEI)

27

AMP board

MAIN board 

TRANS board

TC board

PANEL board

DISPLAY board

FRONT INPUT board

VOL board

VOL SEL board

SUB POWER board 

MOTOR board

DRIVER board

TRAY SENSOR board

DISK SENSOR board

BD board

IN OUT SW board

28

Note:
• All capacitors are in µF unless otherwise noted.  pF: µµF

50 WV or less are not indicated except for electrolytics
and tantalums.

• All resistors are in 

Ω

 and 

1

/

4

 

W or less unless otherwise

specified.

•

f

: internal component.

•

2

: nonflammable resistor.

•

1

: fusible resistor.

•

C

: panel designation.

• X

: parts extracted from the component side.

• Y

: parts extracted from the conductor side.

•

a

: Through hole.

•

: Pattern from the side which enables seeing.

•

A

: B+ Line.

•

B

: B– Line.

•

H

: adjustment for repair.

• Voltages and waveforms are dc with respect to ground

under no-signal (detuned) conditions.

• Voltages are taken with a VOM (Input impedance 10 M

Ω

).

Voltage variations may be noted due to normal produc-
tion tolerances.

•

∗

: Impossible to measure

• Waveforms are taken with a oscilloscope.

Voltage variations may be noted due to normal produc-
tion tolerances.

• Circled numbers refer to waveforms.

• Signal path.

F

: FM

E

: PB

a

: REC

J

: CD (Analog)

c

: CD (Digital)

• Abbreviation

MX

: Mexican model

KR

: Korea model

Note: The components identified by mark 

0

 or dotted line

with mark 

0

 are critical for safety.

Replace only with part number specified.

C

B

These are omitted.

E

Q

B

These are omitted.

C

E

B

These are omitted.

C

E