>
>> I have a Commander HF-2500 which uses a pair of 3CX800's. Recently I've
>> noticed the plate current does not drop back all the way to zero when
>> un-keying. The longer it's on and the hotter it gets, the higher this
>> current is. It starts out around 50 ma and after a half hour or so of
>> RTTY, will get up to 250-300 ma. If I let it sit with filaments on but
>> not keyed, eventually the current will drop down again.
>>
>> I'm suspecting some out-gassing in one or both of the tubes. I know the
>> previous owner seriously overheated the tubes to the point where the
>> delrin insulators around the tubes were melted.
>>
>> Does this sound like a bad tube or tubes?
>
>It is not necessarily at tube problem, especially if you can drive the
>PA to normal output when it is acting acting up.It is certainly not
>gassing, because that causes a HV anode to grid/cathode
>flashover....a "big bang".
// An arc inside the envelope is barely audible. Big bangs occur in air,
not in near vacuums.
cheers
- R. L. Measures, 805.386.3734,AG6K, www.vcnet.com/measures.
end
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