[Amps] 811A vs 572B

[Hal W5GHZ]

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.
 
Hal W5GHZ


 
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