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[Amps] AL82 repair

To: Amps group <>
Subject: [Amps] AL82 repair
From: Robert W5AJ <>
Date: Wed, 6 Jul 2022 22:08:43 -0500
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Several months ago, I posted an issue with AL82 variable capacitor.
It was the plate Tuning capacitor that had arc'ed across and
After several months of the variable capacitor being on backorder, I found
in the storage bin, the same variable capacitor, but shorter, fewer plates.
Did the transplant of individual plates, replacing damaged plates and
restoring the AL82 Variable capacitor.
On a side note, we departed soon after that transplant to help son move and
forgot about canceling the back ordered capacitor.
It arrived after six + months on backorder.  ooops.

The photo shows the installed RF output vacuum relay.
My general hypothesis was something was failing after the PI network
T/R relay, antenna switch at base of tower, matching network on 80m phased

Amp reflector rejects messages over 30K...
This link shows photo

One of the observations last year was the plate capacitor would start
arc'ing seconds after transmitting (not milliseconds)
The Vacuum relay wasn't intended to run QSK,  something to look at but not
required for this amp.

tested spare 3-500 solo with about 650 watts output on MFJ power/swr meter.
The wattmeter is probably not best for tube output testing accuracy.  The
tube will make a good spare.
Tested Eimac 4-400 solo with about 300 watts output showing.
Seems a bit faded but didn't arc across.  I installed a smaller fuse in
220V and a small single wire between plate cap and parasitic choke before
I have four 4-400 that need to go, not sure it is worth the risk to test in
GG mode.
Going to obtain a new set of 3-500 from RF Parts.

73 Robert W5AJ
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