----- Original Message -----
From: "Roger White" <rwhitete...@verizon.net>
To: <drakelist@zerobeat.net>
Sent: Sunday, July 29, 2012 6:53 PM
Subject: [Drakelist] Removing the Load Variable Capacitor on
a L-7
I have had a Drake L-7 sitting on the shelf unused for a few
years now and recently decided to sell it. It has had the
power supply updated and the ON/OFF switch disassembled and
cleaned. It had functioned OK the last time I had used it (2
years ago) with the only problem being an erratic reading
Plate Amp meter (an quick tap on the meter made it come from
“zero” to the correct reading).
The problem I am having now (and one that has never occurred
before) is the Load Variable Capacitor is appearing to short
some of its plates over a narrow arc of operation (say 10-20
degrees of arc). I can hear the plates touching and, of
course, the resultant negative effect of the power out going
to zero, etc. I have only had the amp open once to clean the
power switch, I could tell it may have been worked, on as
far as the screws on the bottom cover(s) appear to have been
removed at few times.
One thing I have noticed as I looked at the cap with the
cover removed is that I can hear the plates “unshort” if I
“torque” the chassis a little bit or loosen the screw that
holds the front half of the Load Cap to the floor. Has
anyone had this sort of problem with one of the variable
caps? Can the Load var. cap be removed easily?
Thanks for any help in advance.
Roger White W5RDW
Murphy, Texas
One way to find the location of the short is to push a
piece of paper between the plates. If there is a short in
only one place this will find it. Use an ohm meter from
rotor to stator to indicate the short.
If its caused by a particle of something the paper may
also clean it out. You may also have a bent plate. If so
the rotary position of the plates where it shorts is a clue
to the location. Check visually for overall centering of the
plates. If they are off center check the bearing at the back
of the capacitor. You can adjust it to get perfect
centering. If this is from something that has gotten
in-between the plates canned air may also get it out.
--
Richard Knoppow
Los Angeles
WB6KBL
dickb...@ix.netcom.com
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