Hello all.
I have a question on behalf of an Italian friend of mine.
He has 8877 amplifier for 2m and what sounds like some tired tubes. His
'normal' tube is a 3CPX1500. Recently he has noticed that when he tunes
for maximum during tuning his grid current meter goes negative. I
personally have never seen this on either of the two 8877 amplifiers
that I previously ran. He has tried 2 other tubes which do not have this
behaviour although they do produce less output than the tube that
exhibits negative grid current. So I suppose the simple question is what
causes negative grid current on high Mu triode like a 8877? Back
bombardment?
73
Conrad PA5Y
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