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this amp it seems causes some consternation in the repair world,i have one in,that someone who was not qualified, (pedal builder) caused massive damage to,by sticking a meter probe,in the wrong place,outputs/drivers/bias control/various resistors all taken out,i now have the amp working,but the hum and distortion,is pretty up there,the idiot that got hold of this,even ruined most of the control pots,it is running on current limiter,series connected in mains cable,and fed from RS variac,the amp functions with and without the limiter,but common sense says,leave it connected during diags,i tested preamp,separate from pwr amp,that works fine,very low background hum,but seems normal,tracked through with scope,signal clean,Until post pwr amp in,then it all goes haywire,i can not get any kind of stable reading on scope,the 330 uf caps were changed,i fitted 470's at 63v,can see minimal dc on speaker outs,think it was low m/volts 5 or 6 if i remember (9 initially),i was wondering if u10-11 could be suspect,i replaced one of the pair,other was not avail,also existing measured ok,obviously may be falling down on load,i have spent an insane,amount of time on this,along with another eng,from that well known tone factory in bletchley,i got some great advice a little while back,from j.m fahey and i think also enzo,re mosfet 350 trace elliot bass amp,which i am very grateful for,i have written plenty here,as you all can see,i hope this gets the ball rolling,on helping repairers really get au fait with these amps,and the fair number fender made along the same lines cheers folks.steve