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New valves installed, but....

Posted by simond (A) on January 20, 2005 at 02:33:44

In Reply to: Re: Caps - 1000MFD doable + Bias some success... posted by kentaja@yahoo.com on January 19, 2005 at 10:16:00:

... I'm not sure if they are a matched quad or two matched pairs!?

I dropped the bias to 30ma as you suggested (very good tip - the current shot straight up to 55 on the new one I was monitoring during start up). However the other valve on that cahnnel was reading around 30ma (which is where I set it before removing the old valves).

Went across to the other pair and got the same readings: one at 55 the other at 30. I wasn't expecting that at all, I mean I'm still learning about this but my expectation was, that if I removed a matched quad at 30ma, pop in in a new matched quad I would get roughly equal readings on all four, not the 55,30 55,30 I saw.

Is what I'm seeing normal (the tubes I pulled out were old after all, and the bias was set for them) - but the correlation of two similar pairs of readings worries me. I trust the guy who sold me the valves, but before I go back to him, am I justified in my suspicions?

I've set them all to 65ma but have not listened to the amp yet (still waiting for them to settle).

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