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Old 11-28-2006, 12:56 PM
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wcarroll wcarroll is offline
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Join Date: Nov 2004
Location: Baton Rouge, LA
Posts: 75
John, Had the chassis powered up last night on the bench for about an hour. Seems that the grid bias on the r-y amp is staying at the higher 12 volts now... no more back and forth going on. Perhaps something decided to fail completely.

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The cap is a possibility, though. Is it a purple mylar thing? Ceramic disc?
It is a dull-orange mylar ---- like an orange drop but not shiney.

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What this really sounds like to me is a gassy tube. You get slow grid bias change over time. I read up above that you switched the tubes to eliminate this, right? Are you sure they really got switched?
Yes, I tried swapping the tubes again. There is a third 6cg7 in another section that I rotated in as well. No change.

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My soldering iron is grounded, so I would instead probably hang an ohmmeter across the resistor and heat it up with the set shut off.
Haven't tried this yet. May see if I can do it tonight.

Again, thanks for the tips/suggestions!

Wes
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