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TROUBLESHOOTING
(RADIO/GENERAL
SECTION)
GENERAL
SYMPTOM
DEFECTIVE
CIRCUIT
DEFECTIVE
POINT & POSSIBLE CAUSE
No
power
Power supply circuit
* Check whether fuse F701 is blown.
* Check connection between power supply cable and CN701.
* Check Q723 and Q707.
ACC circuit
* Check Q721 and IC701.
Front panel detect circuit
* Check Q721 and improper
connection
of SW601.
Power On/Off circuit
* Check IC702 and Q722. Check for poor connection
between detachable
connector
CN601 and CN901
in switch PCB.
No sound or
Power amplifier
* Check if speaker terminals
of CN701 shortcircuit
to
insufficient
power supply or ground.
sound
* Check stand-by
voltage of pin 7 of IC402 and IC403.
* Check input and output of IC402, IC403 to decide
whether power IC'S are functioning
well.
Line amplifier
* Check input and output of IC401 to decide whether
IC is functioning
well.
E-VOL circuit
* Check input and output of IC301 and pins 27, 28
(CLK, DATA) to decide whether
IC is functioning
well.
Mute circuit
* Check for short circuit between
emitter and collector
of Q401, Q402, Q403 and Q404.
* Check Q601, Q604, Q605, Q701 and then check
mute voltage at Q401 base.
Power supply circuit
* CheckQ713,
Q707, Q708 and then check
whether 8V is output at Q708 emitter.
Electronic
sound
E–VOL circuit
* Check IC301 and output at pins 38 and 39 of IC601.
controls (VOIJ
BASITREIBAU
Front panel connection
* Check for poor electrical contact between
detachable
FAD) inoperative
connector
CN601 and CN901 in switch PCB.
ESE function
ESE circuit
* Check pins 12 and 19 (output) of IC302 and pins
inoperative
16, 17 (CLK, DATA).
Front panel connection
* Check for poor electrical contact between detachable
connector
CN601 and CN901 in switch PCB.
No
ACC switch circuit
* Check 709 and Q71 O.
illumination
Front panel
in Front panel
* Check each LED.
* Check for poor electrical contact between detachable
connector
CN601 and CN901 in switch PCB.
LCD no
LCD back light
* Check whether
PL901 is defective.
display
* Check Q706, Q705, Q704, Q703.
* Check output of pin 26 (Light) of IC601.
Front panel
' Check LCD driver IC901.
(Switch PCB)
* Check LCDOI.
* Check for poor electrical contact between detachable
~ connector
CN601 and CN901 in switch PCB.
* Check output at pins 14, 15 and 16 of microprocessor IC601.
–44–
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