HCD-S500HDE, NAS-SC500PK, SS-S500HDE - Sony Audio Service Manual (repair manual). Page 6

DISCHARGE  PROCESSING
1.  Switching power block on primary side of MAIN board
 

Though high voltage of 280 V is applied to the electrolytic 
capacitor (C205), in about 3 seconds after the AC cord was 
unplugged, the voltage will lower to 3 to 4 V.

 

However, in the case of standalone MAIN board, the discharge 
time will be long because of small load.

 

The voltage at this time is about 290 V.

 

The voltage becomes half in about 20 seconds after the AC 
cord was unplugged. After that, in about 5 seconds, the voltage 
will lower to about 3 V rapidly.

  Then, the discharge slows and accordingly the forced dis-

charge processing is necessary.
•  Forced discharge processing method
  Connect a resistor such as 100 Ω/3 W to the terminals of 

C205 and execute the discharge processing. (Discharge for 
about 10 seconds)

Note: The potential of about 145 V exists across aluminum case of C205. 

You could get an electric shock if you touch the aluminum case of 
C205.

2.  Power block on secondary side of MAIN board
 

In about 3 seconds after the AC cord was unplugged, almost all 
potentials will lower to below 3 V, but after that the discharge 
slows and accordingly the forced discharge processing is nec-
essary.
•  Forced discharge processing method
  Connect a resistor such as 100 Ω/3 W to the terminals of 

C308 and C310, and execute the discharge processing. (Dis-
charge for about 5 seconds)

 

For electrolytic capacitors other than C205, 308 and 310, the 
discharge processing is executed simultaneously with the 
above discharge processing, and therefore the forced discharge 
processing is not necessary.

Ω/3 W

Ω/3 W

Ω/3 W