Variable caps

[Thomas Beltran]

> I don't understand why you would want to put an "abrasive" (however
> slight) lubricant on a bearing.  Especially on a precision drive screw
> where ANY wear could affect the linearity and mechanical stability of
> the PTO.
>
Anti-seize compound is an abrasive?

> My understanding is that "conductive grease" is designed primarily for
> protection from corrosion in electrical connections, NOT for
> lubrication.  Hence it's availability from power line crews??!?!
>
Rob Sherwood recommends some type of conductive grease.  The stuff sold
locally, is a lithium grease with additives to make it conductive - I have
it somewhere, but I didn't think it is graphite.


> Certainly Drake NEVER recommended any lubrication on the PTO drive
> screw other than a single drop of light oil.

I think you later respond to your own statement - neither did Drake, or
probably any manufacturer of the time expect that, at least 30 years later,
their equipment would still be in use.  The then-current recommendations of
a manufacturer should be balanced against the condition and needs of a
radio, now some decades later.

>Lithium grease is an
> improvement over the grease that was originally used in the front ball
> bearing, and any question of electrical grounding was permanently
> resolved by the addition of a braid grounding strip on late 4 and all
> 7 series PTO's.

I think the specifics of the Drake is probably beyond this list, but my
radio in questions, R4C # 28715 did not have the braid - I did install it
though.
>
> I have several Drake PTO's over 35 years old, and once the original
> hardened bearing grease was removed and replaced with lithium grease
> no further problems occurred.  The original grease was probably more
> than adequate for "normal life", and I'm sure the Drake engineers had
> no idea that their equipment would still be in daily use almost 50
> years later!

This is why, one has to make repair decisions, based not strictly upon the
recommendations of the manufacturer (who had no idea what the future might
hold for their equipment), but on addressing an appropriate resolution of a
current problem.

Until a while ago, I had three complete C lines.  My background is in
mechanics and machining, and this particular radio was the hottest of the
bunch (that is of course another topic), but the VFO felt bad - almost
unusable.  I tried numerous things to get it to the "feel" of the other
radios.  This particular setup, with the anti-seize compound made it feel
quite nice.  I have used it this way for at least 1 1/2 years with no
problems, and, it has the best feel of the bunch.  As far as the bearing
grease, I cannot recall what I used, but I had the PTO and gear assembly
apart many times, trying different configurations.  What I have now, works
quite well.

>
> I have never found a variable capacitor grounding wiper that failed to
> respond to a drop or two of DeoxiT, and keep the grease in the bearing
> a lubricant, not an abrasive.
>
> 73, Garey - K4OAH
> Atlanta
>
> ----- Original Message -----
> From: "Thomas Beltran" <tbeltran at EARTHLINK.NET>
>
>
> > > This is basically a grease that is loaded up
> > > with either nickel or copper (appearing grey, or coppery,
> > > respectively).  That might be what you're wanting...
> >
> > I tried the conductive grease on the Drake PTO screw, but it seemed
> to stick
> > a bit; it was then that I tried the anti-seize compound (it is a
> > silvery-grey, like metal-flake paint) - it worked great.  I first
> clean
> > everything as good as I can with contact-cleaner.  Tom W6EIJ
> >
>
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