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Re: [Amps] Clippertion L 572B tubes

To: "'John.'" <>,"'STEVEN & NANCY FRAASCH'" <>
Subject: Re: [Amps] Clippertion L 572B tubes
From: "Robert Bonner" <>
Date: Tue, 10 Jul 2007 19:00:00 -0500
List-post: <>
I gotta 6L6 I'll send ya will that help?

-----Original Message-----
From: [] On
Behalf Of John.
Sent: Tuesday, July 10, 2007 12:46 PM
Subject: Re: [Amps] Clippertion L 572B tubes

Thanks for the info, The amp does not have any tubes in it and I have 
none. Would like to find at lest one to start the testing.
Thanks again de John KØCQW


>Don't go too crazy replacing tubes.  More often that not, a tube is still
quite good after years of use.  Assuming that the filaments are wired in
parallel, plug one tube into the amp at a time, key the amp and monitor
quiescent plate current.  The resting current should be within 20% of the
group mean.  If you have an assortment of tubes, I would match them for
resting current (again, checking them one at a time assuming filaments are
parallel connected).  If you have an extreme outlier that has low resting
current, I would suspect that it is weak.  Use tubes with similar gain
together.  The RF transistor industry used to do this by marking BJTs with
an ink to indicate Beta grouping.
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