So my parts arrived today AU$74 ( this includes caps and spares for my ZX450) I removed the caps as described in another post on this site (thanks guys) then removed the PWM controller ( Not in a rush to revisit this job) and fitted the 16 pin socket then the new SG3525ANG. Next I replaced the caps ...

Thanks for that idea I will surely be fitting a socket now.
Parts are ordered should be here in a couple of days, I will be sure to post my progress.

Ok so I checked again with another DMM (of same brand) and got the same readings, also performed the same test on my good working ZX450 and got the same readings, so I think my DMM's don't work so well in AC mode. I am still getting a small 2.6V at the lower position of R109 and No.1 leg position of...

I will get hold of another DMM and retest.

Thanks again Eric D.

I will see if I can get hold of another DMM and retest.

Thanks again Eric D.

Ok Eric all tasks completed (see second pic). Amp powered up well with a 10 amp fuse in line, I got a green LED and the fan was running. When I tested the resistor terminals on the PWM controller side the readings where 10V~ in AC mode and 4.6V in DC mode all of the opposite terminals read zero exce...

Thanks for your help Eric I will do this today and post my results.

I am interested in repairing my faithful old ZX350 amp, I'm in Australia and don't know of any local repair shops and shipping to the US is not viable. As you can see it has a badly burnt FET and some damage to the PCB. I have removed all 6 of what I believe to be the power supply FET's (P55N06). Al...