HCD-V8900, HCD-V8900AV, LBT-V8900AV - Sony Audio Service Manual (repair manual). Page 11

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This model has the self-diagnosis function for the VIDEO and
AUDIO decoder sections.
Immediately after the power on, the self-diagnosis function searches
each operation of IC’s around the mechanism control microcom-
puter (IC701).
The results can be checked by connecting an oscilloscope to TP709
(LED) of the VIDEO board.

Oscilloscope (Waveform)

Symptom

H

L

Light

H

L

1 time blinking

H

L

3 time blinking

No error

DRAM (IC251) error

H

L

2 time blinking

External SRAM (IC751)
error

MPEG decoder (IC201)
error

oscilloscope

VIDEO board
TP709 (LED)

+
–

X901

TP709 (LED)

IC751

IC251

On this mode, the data of the color-bars signal as a picture signal
and the 1kHz sine wave signal as a sound signal are output by the
mechanism control microcomputer (IC701) for video CD signal
check. When measurement of the voltage and waveform on the
VIDEO board, perform it in this mode.
For refernce, the color-bars signal can be observed at J9001 (VIDEO
OUT) and the sound signal can be observed at J101 (VIDEO (AU-
DIO) OUT) using an oscilloscope.
1. Connect the lead wire to both ends of the land of SL701 (CAL

BAR) of the VIDEO board.

2. Turn the power on. Press  FUNCTION  button to select CD.
3. After 2 or 3 seconds later, connect the lead wire.
4. After measuring, remove the lead wire connected.
NOTE:
The 1 kHz sine wave is not outputted when the CD is played once,
but it is not error.

SL703 (AFADJ)

IC751

IC251

SL702 (ADJ)

SL701 (CAL BAR)

• Refer to SECTION 6 ELECTRICAL ADJUSTMENTS page 15.

1. Connect the lead wire to both ends of the land of SL702 (ADJ)

and SL703 (AFADJ) of the VIDEO board.

2. Turn the power on. Press  FUNCTION  button to select CD.
3. Short-circuit the lead wire. (At this time, “DISC” on the fluores-

cent indicator tube will blink (test mode). If it is not blinking,
perform from step 1 again.)

4. Press the  ·  button in playback.
5. Every pressing the  REPEAT  button, the tracking servo and the

sledding servo are turned on or off.

6. When the servo is OFF, the counter on front panel will not be

changed.

7. After measuring, remove the lead wire connected step 1.