[R-390] Update on R390A, open question regarding scope and options for lubrication

[Tisha Hayes]

Gears/cams maintenance became much easier once I purchased an ultrasonic
cleaner. I haven't had to pull apart the geartrain on my two R-390A's in
about ten years.

I slightly touch up any obvious wear-points/corrosion/ galling with a fine
crocus cloth and then put it all in the ultrasonic with Simple Green
aviation mix. Give everything a final rinse with boiling distilled water
and just a few drops of a light synthetic sewing machine oil.

One of the biggest messes was when a previous restorer decided that the
slug inductor bores in the RF deck all needed a liberal dosing of oil and
grease. That was a PITA to clean up as I had to suspend the deck upside
down and shoot contact cleaner upwards and in to the bores to flush out
that trash. All those might 'ever' need is a slight dusting with talc if
you have a draggy slug.

The wear surfaces (edges) on the cams really benefit from a little bit of
polishing. So much of the friction/stiction when tuning is caused by
imperfections in those surfaces.

R-390's are easy when compared to the plate that is inside of a Hammarlund
SP-600. That is nearly impossible to clean.

I sold off my Central Electronics and Gonset radios a few years ago and
mostly work on Harris stuff these days but my two 390A's are keepers.

*Ms. Tisha Hayes, AA4HA*