Trying to remove load & voltage protection of an ATX computer power supply

Thread Starter


Joined Jan 10, 2021
I have ATX model: FSP300-60THA (1). It has FSP3529 inside to monitor overload or over-voltage protection.

At the 9th page, its datasheet said about pin4 (OPP): Overpower detection input. Connect this pin to the drive voltage or current transformer output. When not in use, this pin should be grounded.

I opened the ATX, disconnected pin4 manually from the circuit, and connected it to ground Pin 15.

But, still it does not work. The fan of ATX still works after turning on the power, but it turns off itself when I apply any load.

I will appreciate the expert suggestion.

Thanks :)


Joined Jun 22, 2012
Can you take pictures of inside please, there maybe other chips that sense too.

That chip has 4 over/ under voltage sense pins, 3,5,12 and -12 , any of these out of range will shut down the psu.
Last edited: