Look for discoloration on the anode, it should be a nice flat black.
Also no discoloration of the glass or those little filament support springs
loose in the bottom...or little pieces of filaments.
A heat damaged base is not a good sign either and Im sure you already know
what a tube gone to air looks like inside.
Carl
--------------------------------------------------
From: <qrv@kd4e.com>
Sent: Sunday, January 25, 2015 12:27 PM
To: <amps@contesting.com>
Subject: Re: [Amps] What 811A's Should I Try to Find?
Carl,
Since everything I read says 100 -> 600 -> 1200 watts are the
meaningful points where the receiving station notices a difference I
can see no reason to push it beyond 600w.
Thanks re. the recommended tubes - I'll keep my eyes open.
Any obvious visual symptoms of a bad tube or a soft tube -
apart from a power tube capable tester?
Thanks again - David
Any USA brand, RCA, GE, Raytheon, KenRad, Cetron, etc. Go for the latest
date codes
into the 70-80's.
Ive seen them mixed up in the 30L1 used by the USAF so Im half assuming
they
are all built to close tolerances that matching isnt required.
And don't for a minute think you can abuse them either as those paper
thin anodes will melt
holes in them almost as easily as the Chinese.
If you run that amp at 600-650W out instead of 800 they will last a long
time.
Carl
KM1H
--------------------------------------------------
I captured and saved VK1OD's abandoned page re. the 811H
and associated tubes.
I've also been reading threads here, and elsewhere.
When I'm at Hamfests and have an opportunity to buy or trade
for some 811A's - which manufacturer (and/or perhaps also date)
should I look for, please?
Thanks - David KD4E
--
*David*
~KD4E~
Nevils, Georgia USA
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