12v PSU help please.

[CraigR]

I have a 12v psu from a DJ lighting system and I can not seem to figure this one out. The board so far had a blown fuse and a shorted voltage regulator. After replacing those I get 12v out but hooking a load to it the voltage seems to bounce between 5v and 0v. I remove all the caps and checked those and replaced 2 that were only questionable. I know it's not the device I connect it to as I put 12v to it with my bench power source and it works fine.

[Diah]

this the same used with Chinese projector,,, the issue will be at out put,,,because the AC circuit damaged transformer Ohm value changed.... and so on...... this why always i use universal circuit to replace it complete

[CapLeaker]

Where is there a voltage regulator? Did you check the main filter capacitor too or just the output caps?

[CraigR]

Where is there a voltage regulator? Did you check the main filter capacitor too or just the output caps?

I meant mosfet not regulator and yes pulled and checked all caps.

[CapLeaker]

I meant mosfet not regulator and yes pulled and checked all caps.

Which caps did you replace? The output ones? Can you upload some high resolution pictures top and bottom and from the side, so we can see the components.

[R_J]

Was the mosfet shorted Drain to Gate? if it was then it is possible the ic was damaged, also check the source resistor (if there is one) and there may also be a resistor between the mosfet source and the CS pin of the ic. You should also replace the small electrolytic in the primary circuit.

[stj]

try replacing the output diodes.

[CraigR]

I found it to be a bad resistor reading high.