>>With cutoff bias supplied, the tubes SHOULD be incapable of drawing
>>virtually any anode current, Chad. Something else seems to have been
>>going on. The inconsistency of melt-downs makes me suspicious. Did
>>anyone ever measure the resistance of the VHF suppressor resistor after a
>>meltdown?
>
>We couldn't (if I remember correctly) because everything up to the DC
>blocking cap was toast. The DC blocking cap is directly on the plate
>tuning vac variable.
>
To me, Chad, your "because" does not make technical sense.. The VHF
suppressor resistor is DC-protected by a 30nH to 100nH parallel
inductance. Barring an all-out assualt by rival contesters armed with
flame-throwers, it Should have been possible to test this resistor.
>From my own experiences, when the failure mechanism is mysterious, as is
the case here, it pays to check EVERYTHING. IMO, a high-pot is virtually
essential to troubleshooting a tube-type amplifier--even thought it
useless for checking VHF suppressors. For that job, one needs a
soldering iron and ohmmeter. Resistors can NOT be accurately evaluated
by appearance. .
Rich---
R. L. Measures, 805-386-3734, AG6K
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