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Author Topic: Ameritron 80B negative grid current on power up  (Read 2168 times)
W1QJ
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« Reply #15 on: June 01, 2017, 07:47:55 PM »

What do you want to know?
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K8AXW
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« Reply #16 on: June 02, 2017, 07:12:57 AM »

Louis, specifically is there anything in the bias circuit that could cause this problem?
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VE3LYB
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« Reply #17 on: June 02, 2017, 12:25:20 PM »

This appears to be a grid to filament short issue as suggested.

I replaced tube with a spare (which has significantly lower output).

Negative grid current problem is not present with spare tube installed.
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W1QJ
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« Reply #18 on: June 02, 2017, 01:29:32 PM »

This appears to be a grid to filament short issue as suggested.

I replaced tube with a spare (which has significantly lower output).

Negative grid current problem is not present with spare tube installed.
There's your answer. Just as I suspected.  AWX, no, nothing I know of in the bias circuit would cause negative grid current reading.  The only thing that would be a bias problem in standby mode would be a loss of cut off bias which won't show negative grid current.  Loss of cut off bias would be plate current draw. 
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K8AXW
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« Reply #19 on: June 02, 2017, 10:42:27 PM »

TY Louis.  I'm glad he got the answer he needed and I learned something as well. 
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