|[AMRadio] Screen Modulated 813|
ars.w5omr at gmail.com
Mon Dec 11 19:27:56 EST 2006
SBJohnston at aol.com wrote:
> brett.gazdzinski at verizonbusiness.com writes:
>> Most 813's had graphite plates, and I never remember
>> them showing color, I always thought that would be way beyond
>> what they were good for, or was good for them...if they were glowing!
> I was testing my single-813 grounded-grid amp the other day and had it making
> 500 watts out cw. The plate was a bit red at peak output, but getting very
> red fast off the peak of the tuning.
You probably saw a rise in plate current, as well. Off-resonance.
I've had 250TH's in my rig (balanced, cross-neutralized, link-coupled)
and had one show color, while the other did not.
Different brands of tubes.. different plate configurations...
differences all over. but, they still dipped at the same place, and
drew the same amount of current off-resonance, and drew different shades
of red, depending on which tube you look at.
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