Solid State Guitar Amp Forum | DIY Guitar Amplifiers

Hi Folks
Hving succesfuly fixed an Ashdown with some great advice from Enzo Roly and JM Fahey. I've now moved on to another repair, a Warwick xtreme 10.1. It had blown lots of stuff including most of the output transistors, the drivers and all the transistors to from the diff amp onwards (bias stuff etc). I replaced it all and it seems ok now except I have about 65mV of DC at the output. Is that too high or is it an acceptable amount? if not how do I adjust it out?

And yes I know the attached schem is from the tube path 10 but the power board in this amp is the same, with a few additions from the xtreme 10
Cheers
Shane

On the output stage circuit (PDF page 4/11) there is a pot shown in the emitter circuit of the input differential pair marked "P2" - my guess is that this is the trim to bring the residual output voltage to zero.

The amp should be allowed to warm up, say for 10-15 mins, and the idle current should be correctly set (again I'll guess at 10mA for each of the six output pairs), the input shorted, no load connected; then the trim pot carefully set for as small a residual as can be managed.

Thanks again Roly, managed to get it down to about 20mV. I think it'll be OK at that seems to work fine anyway!

Cheers
Shane

65mv is not a big deal.  20mv is better.  Was that with a load or without?   If that was without a load, does the offset disappear when the load is applied?