> BTW, gud deal..only $102.00 matched) one of the tubes went into parasitic
> oscillation and before I could kill the main power switch it finally
> killed the circuit breakers. Now this one tube has a burn spot on both
> sides of the anode and the tube glass adjacent to it is mirrored. Does
> this necessarily mean the tube is weakened/not matched to the other
> tube?? I don't have a hi-pot to test them.
Well, it might be good....or it might not.
I have another suggestion. When testing for oscillations, put a large
value high wattage resistor in the filament return to the B minus.
Normally I put a large high wattage lamp in series with the return,
just be absolutely sure the insulation is good and the negative rail
of the supply is clamped to the chassis through a big protection
diode.
Then you can let the tube oscillate while you run for the switch. A
good idea is also to FUSE the HV supply for a reasonable current.
Fuses, even by the dozen, are cheaper than tubes.
73, Tom W8JI
w8ji@contesting.com
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