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[Amps] 811A vs 572B

Subject: [Amps] 811A vs 572B
From: Hal W5GHZ <>
Date: Sun, 13 Feb 2011 19:44:09 -0800 (PST)
List-post: <">>
My AL811H just went into VHF parasitic oscillation and took out a brand new set 
of 811A's, plate choke, several capacitors and a couple of resistors and the 
fuses.  This is the second time this has happened.  Guess it is time to rebuild 
this amp from the ground up with all of the new parasitic supression techniques 
and an enhanced power supply (six filter caps instead of four).  I will also be 
putting in the 572B's.
I have an old Heathkit SB200 and with new tubes and it easily puts out 900 
watts into a 50 ohm dummy load with the currents all in spec.  However, I run 
it at 600 watts.  The AL-811H used to run 800 watts until it started acting 
like a two meter MPO.

The fish are biting. 
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