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In Reply to: RE: 450v plate and screen? posted by Alpha Al on June 08, 2017 at 13:56:49
"I was mostly curious why the hot area was so small, instead of the whole plate heating evenly."
I think it's always that way with beam power tubes. The beam deflector plates force the electrons to that area of the plate.
Is the bias voltage adjustable?
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Follow Ups:
Yes, the bias is adjustable. If I reduce plate current down to 12 mA, the hot spots disappear completely, but the power and tone quality suffer.
12ma 450 vdc is only 5.4 watts
Something is wrong with those tubes.
The plate of the 6v6gt should be good for 12 watts without glowing.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Maybe a good idea to check all lines going to and from the 6V6GT. If over 5.4 watts per tube causes the tube anodes to glow red --- something is definitely amiss. I'd check any bypass cap and grid-to-ground resistors, along with other suspects.
Have you tried other know, good 6V6GT tubes?
Good luck!
8^)
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