• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Newbie- Tube Testing RF Amp tube

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jsternmd

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Joined 2011
I am replacing a pair of 6293 (similar to 6146A) for my ham HF tranceiver. On testing a batch of NOS 6293 on a Hickok 539C, I find the occasional high outlier. Most of them test around 8800-1000 Gm with plate currents around 55-65ma (tube data shows min Gm 4600). Every once in a while I find a tube with real high Gm values almost double ~ 17,000 with lower plate current ~50ma. Is this due to a bad tube oscillating? Any special technique to test such a tube?

tia
jerry
 
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