Meat Plow wrote in message
...
On Sat, 22 Nov 2008 16:36:08 -0000, "N_Cook" wrote:

What would cause the failure of one half of a 4 year old 12AX7 ? A very
careful owner.
One half tests out fine but for half using pins 1,2,3 cannot get any
zeroing
on the tester even setting current down to 0.5 mA or less and for any
grid
voltage setting. Can't see any obvious internal weld failure.

Maybe a break in the grid wire near its winding start? Does the
filament glow on that side? Is the cathode shorted to the filament?


No C/H leakage either triode. Can only see heater glow with this make of
tube, badged GT if relevant, by viewing underside of envelope. Both heaters
equally bright.


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