I have a standard PC PSU that I pulled to use as a bench supply unit. It seemed to work fine for a while and then I think something shorted while using it so I set it aside to look at it later. What happened was the resistive load wire broke so it wouldn't power on. Fixed this.
I pulled the unit today and it seemed to be working and I pulled the board from the metal case to put it on my project board and now it isn't working. I turn it on and I get about 6-8v on the 12v rail and it drops about .75v every second or so until it hits .49v and sits there. Power off the unit and after about 20-30 seconds I hear a little click and the voltage starts to drop to zero. I don't get any voltage on the 5 or 3.3v rails. I think this PSU has some jumpers that run the power from the 12v, through a resistor, into the 5, through the jumper, into another resistor, into the 3.3. IDK if that is standard on other supplies but I was able to trace that on this unit.
Can anyone give me any insight on what might be the issue or where to start looking here? This is a nice supply that has adjustable voltage so I'd like to save it.
I pulled the unit today and it seemed to be working and I pulled the board from the metal case to put it on my project board and now it isn't working. I turn it on and I get about 6-8v on the 12v rail and it drops about .75v every second or so until it hits .49v and sits there. Power off the unit and after about 20-30 seconds I hear a little click and the voltage starts to drop to zero. I don't get any voltage on the 5 or 3.3v rails. I think this PSU has some jumpers that run the power from the 12v, through a resistor, into the 5, through the jumper, into another resistor, into the 3.3. IDK if that is standard on other supplies but I was able to trace that on this unit.
Can anyone give me any insight on what might be the issue or where to start looking here? This is a nice supply that has adjustable voltage so I'd like to save it.