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[Amps] FW: 8877 negative grid current

To: <>
Subject: [Amps] FW: 8877 negative grid current
From: "Matt" <>
Date: Sun, 15 Jul 2018 11:41:34 -0500
List-post: <>
Hi Conrad,

I experienced negative grid current once with an 8877 amp and traced it back
to a poor connection at the ground return of the HV supply.   You might want
to check there first.

Hope this helps.

-----Original Message-----
From: Amps [] On Behalf Of Conrad PA5Y
Sent: Saturday, July 14, 2018 2:21 AM
Subject: [Amps] 8877 negative grid current

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?


Conrad PA5Y

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