View Single Post
Old 25th Sep 2018, 1:41 pm   #7
Diabolical Artificer
Dekatron
 
Diabolical Artificer's Avatar
 
Join Date: Jul 2009
Location: Sleaford, Lincs. UK.
Posts: 7,636
Default Re: 120W PP EL34 amplifier re-born.

Thanks both, at the moment it sounds dire, it's giving me gyp...again. I have a really odd fault. I have a basic common cathode triode gain stage AC coupled into a LTP. Signal in without power, sinewave at the grid of the triode gain stage is perfect. Power on and the sinewave distorts badly, OP is terrible and limited to 1v P-P. Remove the valve in the LTP socket, all is well.

Tried different sig gen's, different valves, same problem. Scoped everywhere, wondered if there was some spurious oscillation, no. Checked DC conditions, fine. Thing is, it was working fine yesterday. Blocking distortion? Doesn't make sense.

Just when I think I'm getting somewhere, wham! Another problem. So resilience, determination, sheer stubborness or just plain stupidity is needed in bucket loads.

It's a nice day, off for a walk and a think.

Thanks for your kind words and interest, Andy.
__________________
Curiosity hasn't killed this cat...so far.
Diabolical Artificer is offline