Hi,
I'm trying to repair this PSU board for a Creative S750 surround sound system.
Original fault was a blown diode (D9 1N4004), I replaced it with a 1N4007 diode. I also replaced U6 7920 negative voltage regulator which used the configuration in the schematic to output -24V , I replaced it with a 7924 while removing R20, C68 and R19.
I also replaced all the crap CAPXON capacitors on the board with quality caps.
The board now outputs all the voltages it's supposed to output correctly with one problem.
When you plug the power cord the green light turns on. When you switch the unit on from the control pod for the first time after you plug the cord I hear something like a spark coming from the relay (I think), If you switch the unit off from the control pod (without unpluging the power cord) and then switch it back on, the relay click is normal without that spark sound.
One time I switched the unit off, unplugged the power cord, and then quickly plugged it in the switched it on, and it blew the D9 again.
My question, what part of this circuit can cause such a sparking sound when being turned on for the first time, or is responsible for a soft starting of the relay (if that is a thing)?
Thanks.
Stand by section of the board:
The section that gets turned on by the relay: