[Amps] FW: Negative grid drive

[maflukey at gmail.com]

I had an AL-1500 do that one time on me.    Turned out to be a poor ground
connection at the rectifier board.   The board was only grounded via
mounting screws to the chassis which had become just loose enough to cause a
little voltage drop.   Tightening the screws fixed the problem, and a
supplemental ground strap is insurance against reoccurrence.

73
Matt
KM5VI





-----Original Message-----
From: Amps <amps-bounces at contesting.com> On Behalf Of Tom Osborne Sr.
Sent: Sunday, August 02, 2020 7:23 PM
To: amps at contesting.com
Subject: [Amps] Negative grid drive

HI All

I have an AL-811h and it has been running just fine with about 600 watts out
with the amp on 110.

Today I turned it on and the grid current went negative with it in standby.
Shut it off real quick as didn't want to let the smoke out of any parts.

What would make the grids go negative?  A bias problem.  Thanks and 73 Tom
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