[R-390] Cleaning R-390 gears in place before lube

[Tom Frobase]

My approach is as follows "from memory";  Set the radio to 7.999 MHz,
Remove the RF deck from the radio.  Remove the crystal oscillator
sub-chassis, remove all of the slug racks and set aside.  Remove all of the
RF and MF cans from the RF chassis, 4/40 screw inside the can accessed from
the top.  Once that is complete loosen the band switch shaft and slide back
into the chassis.  Remove the antenna trimmer shaft.  Once the prior steps
are completed the mechanical portion can be removed.  The mechanical
section is fastened to the chassis with (2) 6/32 machine screws in the rear
and 3 1/4" hex screws in the front.  I use a 1/4" craftsman box end to
remove the hex screws

Separate the mechanical section from the primary chassis.  This will give
you an unimpeded opportunity to clean the top of the electronics chassis, I
usually remove each RF and MF can cover and remove with a toothbrush any
dirt that has accumulated on the trimmer, I do not use solvent other than a
small amount of denatured alcohol on a rag to clean the trimmer top.  I
also use a Q-tip with a little alcohol inside the slug guide tube and wipe
the slugs with a little alcohol.  Set the cans aside for later re-assembly

Remove all slugs and keepers from the racks, don't loose the keepers,
marking slugs and rack position for re-installation.  I then soak and clean
the racks in Sudsy ammonia in a small ultrasonic cleaner.  Each of the
racks contain small ball bearings, I then manually exercise each of the
bearings to make sure that grease has not dried and frozen within the
bearing.  Once done I flush with hot water and dry.

I have the fortune to have a large ultrasonic cleaner, it will contain the
entire mechanical assembly, I drop the assembly into a mild solution of
water based de-greaser and run the ultrasonic cleaner until the gears are
clean, I assist the cleaner with a small brush, I then flush and rinse in
hot water, once this is complete I soak the mechanical assembly in kerosene
overnight to make sure all of the water is displaced from the bronze
bearings.  Then I drain and wipe the mechanical assembly.

I then reassemble the chassis and mechanical assembly making sure the
mechanical alignment markings are correct, re-install the cans, obviously
in the same place.  Re-install the slugs into the rack leaving the
alignment screws at about midpoint.  Re-install the racks into the
mechanical assembly and lubricate the cams and bearings, I usually use
lightweight synthetic car oil, or whatever slick stuff you choose.
 Re-attach the band switch shaft, antenna trimmer and crystal oscillator
sub-assembly.

Turn on the radio crank up the RF generator set at 7.999 and hope for a
tone, if it there realign the radio, if not find out what was missed.

The process is a bit of effort, but at the end of the day, I know that the
radio is clean and smooth running ... 73, tom, N3LLL


On Wed, Jul 30, 2014 at 12:25 PM, Charles Steinmetz <csteinmetz at yandex.com>
wrote:

> Bob wrote:
>
>  I've been down the road with this on a couple of radios. I'd *think* I
>> had everything sprayed out and clean. Eventually something would get me
>> moving and I'd tear down the gear train. There always was an improvement
>> after the tear down. Spraying stuff out of split gears - very tough to do.
>>
>
> Most of the accumulated dirt and grime is just sitting there harmlessly.
>  Some of it gets between the teeth of meshing gears and slows things down,
> and a tiny bit gets into the bearings and between the split gears, but the
> rest is just ugly and does no harm.  UNTIL you start cleaning or
> lubricating it.
>
> The "hose it down in situ" approach (with or without brushing) actually
> washes dirt INTO the bearings and between the split gears.  The only way to
> make sure there is no dirt in the bearings and between the split gears is
> to disassemble the gear train, clean everything down to bare metal, and put
> it together again, lubricating everything LIGHTLY as you go.  This also
> gives you a chance to inspect the gear teeth and the faces of the split
> gears for burrs or other defects and to remove them (carefully, with
> toothpicks, needle files, Xacto blades, small, hard cutting stones, and
> fine grit paper).  That is how one attains the ultimate smoothness of
> operation.
>
> Best regards,
>
> Charles
>
>
>
>
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