[AMPS] vom check of 3-500Z tubes

[2]

>
>> my amp supply lk-500 zb did a funny thing a while back when I powered
>> it up after a long time in the closet and a cross country move.  so
>> far I have found a blown 1 ohm, 5 watt wire wound resistor.  it was in
>> two pieces so there is little debate on whether or not it blew...
>
>Most likely you have a gas problem with the tubes. That is normal 
>for tubes that sit a long time, especially tubes that might have had 
>the seals operated at elevated temperatures prior to sitting.
>
>You can not test that with a VOM. You need  a high voltage tester.
>
>You should have a breakdown of 11kV or more from anode to grid 
>in a good 3-500Z.
>
>The grid is the offset pin, and the two adjacent pins. The remaining two 
>pins are filament.
>
>> one area that was suggested as a potential problem was an internal
>> short in one or both tubes.
>
>Yep, and it most likely is gas.
>
//  However, it could be vanishing gas that disappears seconds before the 
tube is connected to a high-potential tester.  Normal leakage is <10uA @ 
8kV.  If you see >50uA leakage, it's regular gas that blew the 1 ohm, 5 
watt wire wound resistor..  If you see <10uA leakage, it's vanishing gas 
that blew the 1 ohm, 5 watt wire wound resistor.  

cheers

-  R. L. Measures, 805.386.3734, AG6K, www.vcnet.com/measures.  
end


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