I have a LK-500 that had some rework (rather nicely) that added a spark gap on
that tune cap. He used a nickel strap from the cap to the DC blocking cap,
attached the strap to the cap via the back assembly nuts and placed a small "V"
shaped bend in the strap towards the cap frame. Adjust the "V" until the gap
is slightly less than the cap plate spacing. If you have an arc hopefully it
will jump there and save the plates. It does seem to work well.
Randy AB9GO
-----Original Message-----
From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] On
Behalf Of gdaught6@stanford.edu
Sent: Tuesday, September 15, 2009 5:03 PM
To: amps@contesting.com
Subject: [Amps] lk-550 woes
Hi group,
I've got a friend's Amp supply LK-550 with the optional PAC-5 power supply.
The amp is back for the umpteenth time with melted plates on the tune
capacitor. In
previous visits, I've filed, polished, etc. and it runs for a while. Then it
comes back
with melted capacitor plates. This time, I've replaced the capacitor which is
rated at
3500V. The PAC-5 puts out very nearly 4000VDC, and that doesn't drop much at
full output. That's stressing that poor little capacitor pretty hard. Mistune
a bit, or
forget which antenna you're on, and there is a light show in the plate tank.
I'm thinking of reducing the DC voltage, but I don't have a schematic of the
PAC-5.
The big transformer has an unused terminal on the primary, but I don't know
what it
is. Maybe, it's a primary tap that would allow me to drop the voltage a bit.
I can try
to measure it, but perhaps someone on the list knows, or has a schematic and/or
manual for the PAC-5.
Thanks in advance for your responses.
73,
George T Daughters, K6GT
CU in the California QSO Party (CQP)
October 3-4, 2009
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