while repairing Zener diode - pulled two 3-500 Eimac tubes
one had short (all five pins read zero ohms to any other of the five pins)
took shorted tube to shop for a photo. sell tube as sample/light bulb.
Hummm
there is my old, really old car battery charger
tube is bad so why not
place battery charger in 6Vdc position
there are no protective shutdowns in this charger
(multi-tap transformer & one diode)
one clamp on two filament pins
other clamp on grid pin
let's see if grid will "melt" at area of the short
small glow/flash inside - then battery charger current drops to zero
go to 12vdc, no current
Measure ohms at tube pins:
filament good
Grids all connected
No short between filament/grid
shake tube - still OK
shake tube while measuring ohms, still OK
so, do put 3kV on the plate and see what happens??
anyone tried this before?
AL-82 test bed
W5AJ
Robert
Midland, Texas
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