[Amps] testing 572 B tubes

[alan.kaul@att.net]

Does anyone know if there is a way to test 572 B's?

I recently acquired this AMP.  It had "fairly new tubes" -- according to the previous
owner perhaps 20-30 hours on them.  I found I was unable to load it up to more than 400-600W
output and suspected the 500 pf plate bypass cap (which a couple of you mentioned as a possible
problem).  I replaced the plate bypass cap, with a .001 mfd and added a .01 mfd in parallel.
Then I replaced the plate RF choke with  a new choke from RF parts designed for use in
Ameritron and other amps (it specs at 1.5A, 225 uH, 4 KV max).  Then I put it all back
together and fired it up and the power output is pretty much the same as before I
made the changes.

So I am wondering if the TUBES might be a little soft. 

Anyone  have any other ideas??

Please and thanks and best 73 de alan

--
Alan Kaul W6RCL LaCanada, CA 91011
e-mail:  w6rcl at amsat.org
http://
home.att.net/~alan.kaul/index.html