Graphite is always messy, I have gotten it on hands clothes and it is hard to
wash out.
I think perhaps they should not have earned such a reputation. I believe the
problem stems from the
fact that most 813 amplifiers in the early days had untuned inputs and that
they were pushed
harder than they should have been. Mind you these tubes in triode connection
are about like 572B's.
They have even less plate dissipation than 572B's but I suspect the idea of
pushing them to
2kW PEP plate input was just too much. Also, most used 813's I have gotten had
very little
emission left. That is an indication that they were used beyond the point where
if pushed to
get full gallon output they were probably producing a very dirty signal. I
think if you use
a good pair, with tuned input and don't try to push them too hard they will be
just fine. Treat them
as if they were a pair of 575B's.
73
Bill wa4lav
________________________________________
From: Amps [amps-bounces@contesting.com] on behalf of Tom Osborne
[w7why@frontier.com]
Sent: Monday, December 21, 2015 1:57 PM
To: amps@contesting.com
Subject: [Amps] 813's
Why are 813 tubes considered 'dirty'?
I have an old amp in the attic I haven't used for a long time that has a
pair of 813's in it I have read somewhere that they are a very 'dirty'
tube. I'd assume that means lots of spurs or something.
Just wonder why that would be. 73
Tom W7WHY
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