got a yorkville power source to repair after checking found two mosfet in the woofer amp not working change and check for other not working parts change all four mosfet in amp no other bad component found but when i do the lightbulb test the bulb stays on that means there is a short some where but with out the outputs the amp shows no short what could b the cause of the short please help
From what I can see here: https://www.manualslib.com/manual/1526583/Yorkville-Ps12p.html?page=33#manual its a class-D output, so when the FETs blew they probably fried the FET drivers too - and possibly some more upstream components too.
The way to investigate such an amp is remove all the FETs in the relevant channel and 'scope out the switching signals, replacing drivers and chips as necessary until you've established correct switching waveforms - otherwise adding the FETs is likely to just hard-short everything out again.
The way to investigate such an amp is remove all the FETs in the relevant channel and 'scope out the switching signals, replacing drivers and chips as necessary until you've established correct switching waveforms - otherwise adding the FETs is likely to just hard-short everything out again.