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Old 12th Jun 2021, 12:22 am   #12
mark-jacobs
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Join Date: Dec 2009
Location: Tucson, Arizona, USA.
Posts: 34
Default Re: Hickok 539b bias gauge

The early 539B versions they had an external 0 adjust, later version were hermetically sealed and not adjustable, but seemed to vary. You will most likely damage the meter in breaking the seal. Although my 539B bias meter works correctly I use external digital meters to measure bias and plate current, the meters require isolated power supplies.

You may want to compare the meter readings to an external volt meter, it could be the movement is sticking, damaged movement, debris, etc.
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