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Tube DIY Asylum Do It Yourself (DIY) paradise for tube and SET project builders. |
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In Reply to: RE: Maybe the problem is my first filter caps. posted by Tre' on January 13, 2017 at 11:20:44:
I changed them out and the amp worked fine at the shop for almost an hour everything stable with nice audio. Brought the amp home hooked it up was stable for about 10 minutes then the kt90 bias current started to climb and i shut it down when the meter was at 2.0.
So i unhooked the amp and put my 2 chassis amp in place with the same kt90 power tubes. this amp is the same circuit with fixed bias. I hooked everything up and turned it on. Adjusted the bias to .90vdc or 90ma and everything is good. No bias drift the meter is showing no problems. The sound is very nice.
Regarding you picture. That is exactly how i have it with the grid resistor being 50k. The actual bias voltage before the pot is -51vdc. The bad amp is SEUL with Edcor outputs the 2 chassis amp is SE pentode with Electraprint outputs.
I dunno, the fact that it seems to work at the shop and not at home is really pissing me off. cheers.
Edits: 01/13/17
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Follow Ups
- the problem is NOT the first filter caps. - DAK 17:52:56 01/13/17 (0)
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