[Amps] tubes

[Gary Schafer]

carl seyersdahl wrote:
>  This is something I should know , but it seems to have   escaped my memory
> bank. !!
>  I have several 811A's and all of them have oblong shiny spots on the
> plates, and they all glow a dull red under full power in an AL811 amp. Are
> these tubes defective ?? I was running about 70 watts input and about 600
> watts out and all of the tubes show the same symptoms. !!! Thanks for any
> replies.
>  carl / kz5ca       (I g = 90-100 ma.) (Ip 650 +-)
> 
> 

Hi Carl,

Yes they are probably going bad. The shiny spots are the start of holes 
being burned in the plates. 811s should never be run with any color at 
all. Also I think that amp has only 3 tubes? If so you should not run 
more than 450 watts out, no matter what the manufacturer tells you. An 
811A is only good for 150 watts out each. Pushing them harder shortens 
their life.

73
Gary  K4FMX