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

[bill kirkland]

Not sure what a circlip is but try McMaster Carr. Unfortunately they refuse
to ship to Canada (unless you are a business).

It wouldn't surprise me if there are a number of shims in the gear assembly.
There certainly are in the 51j series gear boxes.
The Collins Quality Manual (http://www.jptronics.org/radios/Collins/)
indicates how well the gears were supposed to mate/overlap 
 - which required the use of shims


You are encouraging me to start on mine collection but I still have to get
through the 51J series first.


Bill, Ve3jhu

 
-----Original Message-----
From: r-390-bounces at mailman.qth.net [mailto:r-390-bounces at mailman.qth.net]
On Behalf Of Ken Harpur
Sent: December-21-12 8:24 PM
To: R-390 at mailman.qth.net
Subject: Re: [R-390] R-390A gear train cleaning

Hi Bob,

I've just finished my first gear rain re-build a couple of days ago. I took
the plunge and disassembled it, soaked everything in mineral turpentine for
a few days, removed the stubborn grease with WD-40, a tooth brush and lots
of paper towels and with the excellent reassembly pictorial on the web
http://militaryradio.com/r390a-rfdeck-geartrain.html
  put it all back together.

My gear train is very well worn and although it is much better than it
was...some gears show signs of very heavy use and after breaking the first
two circlips for the split gears regardless of how careful I was, I didn't
risk pulling apart the others. So on my deck I have three split gears that
badly need to be lapped with a stone as Roger suggested as they feel very
gritty when the gears are rubbed together as opposed to the nice smooth feel
they are supposed to be.

Loading up the split gears can be a challenge on some gears...but with
patience and perseverance success awaits. Also, be aware that there are some
very thin washers that go either side of the gear that drives the khz
readout bezel. On my one there were two at the back and two on the front. 

I decided to pull apart the differential assembly...cleaned it with WD-40
and reassembled. I found the way to load the split gears on it was to rest
one gear on the gear it mates to, then load the remaining half of the gear
and using my fingers as a clamp wiggle the gears slightly until they come
together. 

I created extra work for myself though because I removed the geneva drive
and the gear on the bandswitch...it took me a long time to get that set up
again and for the other 390A radios I have I think I'm going to leave the
geneva drive alone.

I learned a lot by doing mine. When I find a source of suitable circlips I
will be getting back into it to smooth up the gears that are catching. The
point is...a newbie can do it! As long as you take your time, work in a
logical fashion and keep referring to the pictorial.
I suppose it depends on what you're comfortable with. There was so much
caked-on grease on my one that I felt disassembly was the best option.

Good luck with it.

Regards,
Ken 
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