[AMPS] AL-811

[km1h@juno.com]

On Wed, 28 Oct 1998 08:32:25 -0500 "Doug Person" <ki6bq@ibm.net> writes:
>
>So, Lane, the question begs to be asked:  If driving the 811a's to 700 
>watts
>out is going to limit the life of these tubes, dosen't using 572b's 
>offer a
>little more headroom here?  Do you think they could handle more drive
>without experiencing shortened life?
>
>Doug -- W4DXV

Much of the failure mode in 811 amps is plate meltdown from over tuning,
etc. The air flow in some of  those cheap amps is marginal as well as
Pi-net design at the highest bands. 
Yes,  the 572B doubles the available dissipation but graphite tubes
require even more air since all brands except for Svetlana use the same
low temperature glass. 

Nothing wrong with using 572B's as long as the limits are understood.

73  Carl  KM1H

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