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Measuring mA with a DMM

I'm trying to bias a tube amplifier using a Sperry 350a digital multimeter.

I'm getting a negative reading when the amp is powered up (-65mA) as opposed to just 65mA.

Any idea as to why?

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Re: Measuring mA with a DMM

The most obvious solution to your problem is that you may have the meter simply connected backwards. To make life easy, Groovetubes sells a thing called a bias probe that makes biasing tube amps a breeze.

Posted on Dec 27, 2007

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