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Re: [Amps] AL82 pi network C2 failure

To: Robert W5AJ <>, 'Tom Hellem' <>, 'Amps group' <>
Subject: Re: [Amps] AL82 pi network C2 failure
From: gudguyham--- via Amps <>
Reply-to: "" <>
Date: Tue, 7 Dec 2021 22:38:12 +0000 (UTC)
List-post: <>
The spacing is more that adequate.  Too lift loading (controlled by op) or 
antenna problem account foray lest 85% of arcing plate tune caps.  My 
assessment is using a vacuum cap is sort of a band aid for other issues.  That 
said, if you want a standard replacement cap I’ve got a few in stock.  Lou

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On Tuesday, December 7, 2021, 3:53 PM, Robert W5AJ <> wrote:

Tom,  could you forward photo of the Vacuum Variable modification?

My AL82 has failed C2 in the output PI network.  My hypothesis is while
operating amp (and a prior command amp) on 80 meters, a failure occurs in
the phased HF2V network.
This could be in relay switching or arcing across the vertical base
insulator (black marks found). 
I've since installed 80m vertical that seems to solve the 80m antenna issue,
if that was the fault.  But the AL82 needs new variable capacitor in Pi
The one in the AL82 seems bit narrow on spacing, a direct replacement is
IF others have replaced said variable capacitor in AL82 or done Vacuum
modification on any amp, I'd be interested in outcome.
73 Robert W5AJ

-----Original Message-----
From: Amps [] On Behalf Of Tom Hellem
Sent: Monday, December 6, 2021 5:51 PM
To: Amps group <>
Subject: [Amps] LK800C Help

I have an Amp Supply LK800C TNY that's had a couple previous owners.
Just finished putting in a vac variable tune cap with turns counter, for
which I had to remove and strip the front panel. I noted carefully all the
wires that needed to be hooked back up, but I fear I may have made one
mistake: the Xmit/bypass switch now does not work. So I might have gotten a
couple wires crossed, but the schematic in my possession may not be the
correct one because it shows only a couple wires connected to the switch,
and on my amp there are 5 wires connected to the 3 terminals on this switch.

Can anybody help me out with a schematic? Or is anyone familiar with the
wiring of the switch?
I am reluctant to just start moving wires around.

The amp works, but I can't put it into bypass, it's always in transmit mode.

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