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.
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