SA-WCT780 - Sony Audio Service Manual (repair manual). Page 16

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SA-WCT780
16
SECTION  3
TROUBLESHOOTING
1. ON/STANDBY indicator fl ashes in red (PROTECT)

Note: When the volume level is “0”, power of amplifi er block is turned off, and amplifi er protect diagnosis is not performed.
 
  Set the volume level than “1”.
2.  ON/STANDBY indicator does not light up (Power is not turned on)
ON/STANDBY indicator flashes in 
red. 
(PROTECT)
IC104 on the SW-MAIN board is 
burned out.
ON/STANDBY indicator remains 
flashing in red, when removing the 
speaker connection connector 
(CN109) and turning the power on.
Yes
Yes
Replace the IC104 on the SW-MAIN 
board.
Yes
Yes
Check the speaker cable.
Check and replace the speaker
(SP1).
No
The area surrounding IC104 on the 
SW-MAIN board do not 
short-circuits or opens.
No
Replace the IC104 on the SW-MAIN 
board.
Yes
The voltage of the following is 12 V.
SW-MAIN board: IC109 pin 4
No
Replace the complete SW-MAIN 
board. 
(IC109 on the SW-MAIN board 
might have been damaged)
ON/STANDBY indicator does not 
light up. 
(Power is not turned on)
The voltage of the following is 4.1 V.
SW-POWER board: CN901 pin 9
The voltage of the following is 3.3 V.
SW-MAIN board: IC100 pin 61, 62
Yes
SW-POWER board is damaged.
Yes
Yes
Vibrator (X100) on the SW-MAIN 
board is oscillated after AC input.
Yes
Fuse (F900) on the SW-POWER 
board conduct the electricity.
No
No
Replace the diode (D111) on the 
SW-MAIN board.
No
Replace the vibrator (X100) on the 
SW-MAIN board or complete 
SW-MAIN board.
(IC100 on the SW-MAIN board 
might have been damaged)
The reset signal is inputted to pin 6 
of IC100 on the SW-MAIN board 
after AC input.
Check and repair the area 
surrounding IC101 on the SW-MAIN 
board.  
Yes
Yes
No
Replace the complete SW-MAIN 
board. 
(IC100 on the SW-MAIN board 
might have been damaged)
No
Replace the fuse (F900) on the 
SW-POWER board.
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