Date: Mon, 19 Aug 2024 07:17:31 -0600
From: Tom Hellem <tom.hellem@gmail.com>
To: Mark - N5OT <r-emails@n5ot.com>
Cc: Amps <amps@contesting.com>
Subject: Re: [Amps] I like to think there are no stupid questions
<My LC800 was arcing and tripping out.
<Turned out to be the plate tuning cap.
<Once they start arcing it's tough to fix em. Tried filing and cleaning up
the carbon tracks, <but eventually ended up replacing it with a vac
variable.
<That amp uses 3 x 3cx800A7's.
<I figured it was abused by the previous owner.
<I realize this doesn't exactly answer your question, but might save you
some grief in case <you have the same thing going on.
<Tom
<K0SN
This is why I advocate installing a simple, adjustable spark gap across the
tune cap...
(which also protects the bandswitch) and a 2nd spark gap across the load
cap. These are easily made from brass 6-32 / 8-32 / 10/32 / 1/4-20
hardware. I use brass acorn nuts, which face each other. The acorn nuts
are semi domed....and easily replaced if they get trashed. Brass nuts /
flat washer's etc are used to lock the gap.... sorta like the adjustments
on a vibroplex keyer paddles. Box store items.
Then the gap is set such that the gap will arc before the tune and load
caps arc. Either feeler gauges used and / or a hi-pot tester.
I also install a a pair of adjustable spark gaps on my hb amps, that use
vac tune and vac load caps. If an issue with say a TR relay, connector,
wrong ant, no ant, etc, you don't want 1.5 kw going into a wide open =
infinite swr = load cap welded shut asap. If you think trying to fix an
air variable cap is a bitch, try fixing an air variable load cap. A
bandswitch is also a bitch to replace.
Save yourself some grief.
Jim VE7RF
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