[R-390] Y2K Manual Question

[Don Reaves]

Thanks, all, for the followup comments.  I will have a few extra arrows in
my quiver for making my case about putting something, anything, on that
dry, squeaky clean RF train.  But my friend will counter that his R-390s
aren't in heavy duty service, just occasional light SWL duty and certainly
no band sweeping. So long term there is little friction to overcome.
I tried to find the thorough maintenance list our missing but not forgotten
contributor, Nolan Lee, once posted to see what he mentioned about
lubrication but I can't seem to locate it at the moment. If anyone has a
copy of that, could you email it to me?  Tnx.

Don




On Mon, Jul 15, 2013 at 7:11 PM, Charles P. Steinmetz <
charles_steinmetz at lavabit.com> wrote:

> Don wrote:
>
>  MIL-L-7870 is a general purpose, stable at low temp., instrument oil with
>> anti-oxidation properties.  That part number is superseded by part number
>> MIL-PRF-7870.  7870[D] seems to be the last available revision and Royco
>> lists that oil as commercial part 363.  Anyone disagree with my conclusion
>> that 7870 is the proper citation?
>>
>
> Good detective work!
>
>
>  He likes dry, I like a little Mobile-1
>>
>
> I have used both light oil and dry graphite with good success (when I use
> graphite, I apply it dry, not in a solvent carrier -- I found that the
> graphite left after the solvent evaporated did not lubricate nearly as well
> as graphite applied dry).  The primary application for graphite is in very
> dusty locations (sandstorms, etc.), where the dust can get caught in oil to
> form an abrasive paste.  This may be why your friend doesn't use oil.  If
> so, he should consider keeping the radio room cleaner (if dust getting
> caught in the oil is really a problem for him) or using graphite.  You can
> get by with an unlubricated gear train, but it is not the preferred
> solution.  (I have only once or twice seen a 390/390A used by a ham or SWL
> where dust in the oil was a problem, out of several hundred units.)
>
> When using oil, the lubricity demands are not high -- the tuning mechanism
> is very lightly loaded -- so you don't need extreme pressure or high-speed
> additives.  The most important criterion is that it be non-gumming over
> long periods of time and at somewhat elevated temperature.  Second is some
> corrosion inhibitor, given the different metals used in the gear train.
>  I'm sure there are many oils that fit this description.  I've been using
> and recommending Mobil 1 for 390/390A gear trains (and many other uses)
> since the mid-'70s and it is well-proven.
>
> I have generally avoided grease of any sort, because until very recently
> there weren't any that were as gum-resistant as a fine light synthetic oil.
>  There are some specialized greases available today that meet the
> requirement (e.g., some of the DuPont Krytox products), although the ones
> that do are quite expensive and I see no benefit generally to grease over
> light oil.
>
> Best regards,
>
> Charles
>
>
>
>
>
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-- 
--
Don Reaves  W5OR WD2XSH/15
8101 Barrett Rd. Roland AR 72135
VOIP landline:       501.420.3661