[R-390] R-390A gear train cleaning

[Roger Ruszkowski]

Bob,

Standard leaning practice is to pull the RF deck and all the other decks 
while you are at it.

Prop the receiver front edge up on a couple 2 x 2   blocks as you drop the front panel onto 
the bench.

Pull all the tubes.
Unhook the slug rack springs
and remove the slug racks.

Mostly in the summer time, you hang the gear train 
off the end of a table in the yard.

Then run lots of solvent through the gear train and follow up with
compressed air until you have every thing flushed out.

Mostly it is not necessary to disassemble the gear train.

Once eery few years keeps the gears clean.

Relube with synthetic oil blow that in and work it around.

Do not over load the split gears if you need to rework some of them.

That said that's the easy way and it works.

But !!!! for the real smooth drive..

Pull  all the gears apart then pull all the split pairs apart.

Then flat lap all the gears on a good stone.
The idea is to take the edges and burs off the sheet metal punched gears.

Clean that all up and put it all back together.

Once you have spun the dial on a gear train that has been properly lapped
this way you will always remember what a R390 gear train can really feel like.

Roger AI4NI