[Amps] GS35B Idle current increasing

[Paul Baldock]

I built a GS35B amp a few years back to be used with my home brew AM 
rigs. Initially I set the idle current at around 110mA/4KV requiring 
about -35V bias. Over a few years of very little use the idle current 
drifted up so I increased the bias voltage to get it back down. 
Eventually I was up to -55V with the idle current at around 180mA, 
and so I installed another tube (purchased at the same time as the 
first). Same deal as before, started at -35V, now at -55V.

Is this 2 bad tubes, or could I be doing something wrong? I'm getting 
ready to install a third tube purchased from a different source.

- Paul KW7Y