[Amps] Clippertion L 572B tubes

[John.]

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

STEVEN & NANCY FRAASCH wrote:

>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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