I have cleaned the tuning capacitor on 3 different occassions using
various methods, including compressed air, circuit board cleaner, and
a combination of both. Every time I clean it, it works great for
awhile, then goes back to acting badly again.

Air, and typical circuit-board cleaners will remove dust, and a lot of
surface contaminants. Neither will remove oxide from the contacts, or
lubricate the contacts to prevent metal-to-metal galling.

Any thoughts about this? I suspect there have been previous posts on
the issue, but I didn't find anything...

After you have cleaned it a spot of Vaseline on the wipers will keep it
that way for a lot longer. I use an old ink refill syringe and needle.
You have to give it a good squeeze but it puts lube right where you
want it!

You can buy commercial "tuner clearer/lubricant" sprays, which I
believe combine a cleaning solvent with a light petroleum oil that
remains after the solvent evaporates and acts as a lubricant.

I've also had good luck using some DeOxIt spray on the contact
surfaces of air-variable capacitors, roller inductors, and the like.
It does a decent job at cleaning and deoxidizing the contact surfaces,
and provides some lubrication and protection for the surfaces. A
noisy roller inductor I flushed-and-cleaned four or five years ago
remains clean and noise-free today.

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
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