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previous: Patrick Smith I have an Evans amp (200 watts FET ... -- 1142744618

Re: Evans amp help!

3/19/2006 7:48 AM
R.G.	Re: Evans amp help! It could well be parasitic oscillation. With power MOSFETs, that could well be at over 100MHZ, so many tech scopes might not even see it. The described symptoms seem to fit. Check the gate cirucits of the MOSFETs and ensure that (a) there are stopper resistors of 100R to 1K and that (b) if they're there, they are right at the gate pin and that they're not shorted. Unless the PSU is switching, I would not suspect power supply.

3/19/2006 7:48 AM

R.G.

Re: Evans amp help!

It could well be parasitic oscillation. With power MOSFETs, that could well be at over 100MHZ, so many tech scopes might not even see it. The described symptoms seem to fit.

Check the gate cirucits of the MOSFETs and ensure that (a) there are stopper resistors of 100R to 1K and that (b) if they're there, they are right at the gate pin and that they're not shorted.

Unless the PSU is switching, I would not suspect power supply.

Replies:

Patrick Smith Thanks guys, i really really apprec... -- 3/19/2006 11:29 AM