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Author Topic: HQ-170A circuit oddity ?  (Read 2874 times)
G3RZP
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Posts: 8126




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« Reply #15 on: October 25, 2017, 03:14:27 PM »


Quote
That was what happened with the early computer tubes and I thought it was long corrected in regular production. Quite a lot of equipment has tubes biased well into cutoff for extended periods without damage.

Not that sure it would apply to 6C4s or anything other than twin triodes used in early computer applications, because there wasn't a general requirement. The Eddystone 888 rx didn't get a very long life from the crystal calibrator tube until they put in a big cathode resistor so it drew current but not enough to oscillate.
 

 
 
 
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KM1H
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« Reply #16 on: October 25, 2017, 05:03:38 PM »

Any tube regularly biased deep into cut off would have suffered but they dont.
One weak point about the 6C4 I forgot to mention is it is only a 150 ma filament rather than the more common 300 ma version so it entered life as the 90# weakling.
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