[Amps] GS35B Idle current increasing

[Ron Youvan]

   Paul KW7Y Baldock wrote:

> 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.

   It is possible that the grids are being damaged (by too much drive ?)
rendering less grid wires to control the electron beam.
-- 
   Ron  KA4INM - Youvan's corollary:
                 Every action results in unwanted side effects.