[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...
>
//  Where was it in the circuit?

>one area that was suggested as a potential problem was an internal short in
>one or both tubes.
>
//  If you can see the anoode cooler touching the grid, you have an 
internal short.  

>I pulled them and did a vom check for short vs open across all pin
>combinations.  both tubes are eimac 3-500z
>
>if one looks at the bottom of the tube with the plate away, there are 5
>pins.  one is by itself 

//  This is pin 3.  Count clockwise.  Pins 2, 3, 4 are grid.  Pins 1 and 
5 are filament.

> and the other 4 make up the rest of the array. ... ...

>I would guess that the 3 pin set are connections to the grid and the 2 pin
>set is the filament.
>
>so from a low voltage standpoint, it does not look like there is a short
>between either the filament or the grid and the plate nor between the grid
>and the plate nor between the filament and the grid.  maybe at 3000 vdc,
>things change...
>
>comments?
>
//  If the anode cooler is not touching the grid, I would suspect a 
parasite. 

>jim
>N1NK
>x AB6R
>
>
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>


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


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