Help with class D repair please
 

I have a class D amplifier I am trying to repair. It just keeps blowing fusses. I replaced one of the transistors on the power supply side because it was leaking current when the amp wasn't turned on. The PWM is suppossed to be a fixed frequency varying duty cycle design. I have this this regulated to 12V 1.5 amps. When I turn it on the voltage goes down to 7V because its current limited. I can get it to start switching but at about a 50% duty cycle. I don't have a schematic for this amplifier so I am working in the dark here. Any suggestions.

hey there..im no expert, but you are right..it is current limiting..try check and see if the reference hiccups..also check the output rectifiers on the PSU...there has to be a leaky/SC semi somewhere...

I'll try the output rectifiers. This is really bugging me because I know its something simple. Its like there is a dead short after the switching power supply. With no schematic its a real pain.

it could be the PSU too...maybe you can try to remove the power amplifier and test the power supply...since its a switcher, it needs a load to start..measure the input resistance of the ampl and use a high power resistor of the same value to load the PSU...then try and see if the psu is limiting...atleast this way you can eliminate one possibility