[Amps] Alpha 78 Failure

[Paul Gerhardt]

After a couple of years working well and many thousands of Q's the
Alpha 78 quit.  It still switches to xmit, I can hear the relays,
there is a small amount of grid current but no plate current so I am
thinking that the bias is not switching.  The HV reads normal.  Last
time I worked on it I replaced and reworked some parts on the QSK
board two or three years ago.

Does anyone have an idea of how to troubleshoot this?

Paul

-- 
Paul Gerhardt
K3PG
http://pgerhardt.blogspot.com
QRP ARCI 6674
FP 274
"You must do this work with love or you fail." -- John Muir, from How
to Keep Your Volkswagen Alive