[AMRadio] Tube checker gas check vs real world

[Bill Cotter]

Hi Charlie,

I have always been suspicious of the gas-testing abilities of my 
Hickok 6000's and TV-2C/U. After flashing over in my 30L-1, I 
decided to test all the spare 811A's I happened to have. None 
measured gassy on the Hickok.

When testing these dozen or so 811A's, at least six were gassy, and 
of the six gassy tubes four had filament-to-grid shorts (some were 
dead short, some were in the megohms). Unfortunately, the remaining 
six were weak emission. The partially shorted tubes did not 
indicate short on the Hickoks.

I now use a commercial 10kV Hi-Pot tester to test all tubes (811A, 
572B, 4-400, 3-500, 4-1000, etc). I get a strong blue glow on some 
tubes where the gas level is high, others a high leakage current 
value near or below the operating voltage point.

73 Bill N4LG








At 10:41 AM 3/31/2021, CL in NC via AMRadio wrote:
>I have an old Hickok tube tester that can run a gas check.  What 
>is the real world experience with tubes that pass the gas (ha ha) 
>test on the tube checker, vs being gassy when in a circuit?
>While the information about the gas test says it is aimed at 
>amplifier tubes, guessing they mean primarily, audio amps.  What 
>are your thoughts on testing 572B's for gas?  If they pass the 
>test in a checker that uses comparatively low voltages, guessing 
>that does not mean when I put 2100 on the plate of a 572B it won't 
>flash over.
>
>Charlie, W4MEC in NC
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