1600w power supply repair

[Behzad4335]

Hello guys
I have a 1600w netpower power supply which I'm trying to fix it.
The power supply has pfc part ,bridge converter and a 6 watt cooling fan which is placed and supplied from 12v out put voltage.
When the power is turned on without any output load ,even it's cooling fan all things are OK, including pfc and output voltage.
But turning the power with its low power output fan shows a strange thing.
The power supply starts to sink high rate of energy from the network without delivering it to the bridge.
The pfc voltage drop to 375v and the pfc mosfet gate signals become so wide contrary of the very narrow gate pulses of both sides of bridge.
So I included that the energy is sent back to the network through the pfc mosfet.
Anyone could explain me what fault is there?

 

[KlausST]

Hi,

did you check input capacitors - or electrolytics capacitors generally?
A bulge on the top is a sign for defective capacitors.

Maybe it´s a good idea to send some photos.

Klaus

 

[Behzad4335]

Hi,

did you check input capacitors - or electrolytics capacitors generally?
A bulge on the top is a sign for defective capacitors.

Maybe it´s a good idea to send some photos.

Klaus

Dear klaus
Thank you for you reply
I have checked and even replaced all the input capacitors.
What I have founded the day before is that I comp pin voltage in 3pcs01 ic get into 1 to 5 volts which is wrong
So the problem is in the control loop of pfc ic but I can't undrestand why
I wI'll take some photos from my oscilloscope