[R-390] R-390 Woes

Thu Oct 9 12:45:48 EDT 2025

Naptha is a very effective grease and oil solvent.  I used it to clean the gear-train in my R390.

Barry - N4BUQ

> Hi
> 
> As you do this, keep in mind that the “common wisdom” many decades ago was to
> lube the geartrain like crazy. That was what a kid back in the 60’s likely
> would be told to do. The lube used could be just about anything you can
> imagine. Just as now kids got their information from a “range of sources” :) :)
> 
> Fortunately synthetic lubes did not often come up “way back then”. Many of them
> are nearly immune to various solvents and cleaning approaches. The idea that
> they “never harden” may not have taken a 60 year sort of time period plus dust
> into account.
> 
> In some cases a pretty involved process could be involved to clean up after some
> kid from 60 years ago.
> 
> Bob
> 
>> On Oct 9, 2025, at 11:31 AM, Jim Whartenby via R-390 <r-390 at mailman.qth.net>
>> wrote:
>> 
>> Thanks Francesco!
>> 
>> It takes several hours to do a proper cleaning of the geartrain to remove all of
>> the old grease.  I have used WD-40 as a solvent and Krud Kutter as a detergent
>> since it seems that no one product can remove all of the grime.  I have found
>> that old spray bottles are great for applying the cleaning liquids.  Rinse with
>> water after each application, it will take several cycles to remove years of
>> crud.  An acid brush on a wood dowel is used to go deep into the geartrain.
>> Finish with a final water rinse and then an alcohol rinse to release the
>> water.  Now a thin wood skewer is used to deposit a small drop of your favorite
>> synthetic oil to each gear bearing which completes the process.  Do not lube
>> the gears themselves.  The less lube you use the better, it will prevent dust
>> and dirt from fouling the geartrain over the next 20 years!
>> 
>> You will be very surprised how easy it is to now turn the two frequency knobs, I
>> know I was.  That "R-390 wrist" will be a thing of the past.  Don't forget to
>> dab some synthetic oil on the guide rollers and bearings found on the slug
>> racks, they will need some lubrication too.
>> Regards,
>> Jim
>> Logic: Method used to arrive at the wrong conclusion, with confidence.  Murphy
>> 
>>    On Wednesday, October 8, 2025 at 01:59:57 AM CDT, Francesco Ledda
>>    <k5urg at yahoo.com> wrote:
>> 
>> 👍
>> Sent from my iPhone
>> 
>> On Oct 7, 2025, at 23:20, Jim Whartenby via R-390 <r-390 at mailman.qth.net> wrote:
>> 
>> 
>> 
>> For the life of me, I don't understand why people grease the R-390 geartrain.
>> The manual even says that it is better to not grease then to over grease.  The
>> group that knows the most about gear works, in general, are the clock
>> collectors.  Their advise is to sparingly oil pivot points and do nothing to
>> the gear teeth.  It will only collect dust and gum up the works, if you do.  As
>> for the R-390 or is it an R-390A?  First, test all tubes, IRAN, second reseat
>> all connectors, then test again.
>> Regards,
>> Jim
>> 
>> Logic: Method used to arrive at the wrong conclusion, with confidence.  Murphy
>> 
>>    On Tuesday, October 7, 2025 at 03:56:50 PM CDT, Adam Morehouse
>>    <morehouse90 at gmail.com> wrote:
>> 
>> Hey guys,
>> 
>> I appreciate the pointers on my R-392, and now that it's buttoned up, it's
>> time to work on my R-390. I only tested this briefly when I first got it,
>> today I threw it up on the bench. Supposedly this was restored by Rick
>> Mish, it is very clean (except the gear train, which has a lot of fresh
>> grease...), and the front panel is pristine.
>> 
>> It does pull stations, but the volume is extremely low in AGC mode, and
>> gets slightly louder when placed into MGC.
>> 
>> In MGC, with the BFO switched on, it plays at a normal (not super loud, but
>> loud) volume.
>> In AGC, with the BFO switched on, it hums, low volume audio.
>> 
>> The limiter seems to have no effect, and varying the BFO doesn't do
>> anything at all no matter AGC/MGC.
>> 
>> I have Tom's solid state kit installed, and B+ at the AF deck test point is
>> a steady 180.5vdc.
>> 
>> I am going to dig out the TM's later on, I have them somewhere...but maybe
>> somebody here can help point me in the right direction.
>> 
>> Thanks!
>> 
>> Adam K2AAM
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