>
>
>> >> >The Henry amplifiers using 3-500 tubes are quite mature and stable,
>> >>
>Rich writes,
>
>> >
>> ? Four defective 3-500Z tubes with grid-fil. shorts from Eimac seems
>> doubtful. If the tubes came with grid/fil shorts, where did the big-bang
>> and fireworks come from?
>> - - Always blame the other guy.
>> (see photo of grid-fil. short on page 15 of Sept., 1990 *QST*).
>>
>
>Even MORE doubtful is TWO separate amplifiers would make tubes blow up in
>the same day.
? ... your version, not mine. . The two events reportedly took place
years apart in two 3K-A amplifiers. The tubes did not "blow up". They
shorted the same day they were placed in service. The tubes in question
initially produced normal output. In each case, there was an arc and
big-bang. Subsequently, both tubes were found to be grid-fil. shorted.
Both tubes shorting at the same time is quite unusual. SB-220s, TL922s
typically short only one tube per event.
- cheers, Dan
Rich...
R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures
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