[R-390] Interesting Problem

[Norman Ryan]

 Hi, Ron,
If you want to lube the gear train without dismantling it, plan on wiping any old grease off the gears, then apply minimal amounts of oil on the gear teeth.
A good lubricant is Mobil 1 Synthetic SAE75W-90.  I find it tends to stay put and is chemically very stable.  Just be sure to lubricate sparingly.
Best result are obtained by taking the gear train apart, cleaning the parts thoroughly with suitable solvent like paint thinner, then lubing and reassembling.  I've done a few gear trains this way, but find one needs to take extreme care getting them back together properly.  It helps to have another RF deck on hand as a guide.
There is some guidance available on the internet.  Take time to check it out before deciding to go all in.

Best of luck,Norman

    On Tuesday, December 7, 2021, 01:31:05 PM EST, Ron.K3PID <ron.k3pid at sbcglobal.net> wrote:  
 
 So I was shutting down the rig last night and noticed that the R-390 
didn't go dark as it usually does! in fact the OFF position on the function switch didn't 
have any affect on the radio. A quick check with an Ohm meter showed that the 
contacts P118-11 to P118-2 was closed for all positions of the switch. OK! 
Removed the front panel and observed that the cam was indeed pushing the 
microswitch in when in the OFF position. Looking around for an easy way to get 
the microswitch out I just happened to notice that the solder blob on the 
center pin on the switch was just barley touching the unused ( assume Normally 
Open ) pin. It was pretty easy to carefully bend the unused pin away from the 
center pin and Viola! Problem solved!!! Just to be sure I put a piece of heat 
shrink tubing over the unused pin. Now I have never had the front panel off 
before but I have only owned the rig for about 20 of its 65 or so years so I 
don't know what any previous owners had done. It's pretty hard to imagine how 
the wiring harness could have been pulled down enough to get those two contact 
pins to touch but that must be what happened. Why it happened now is a mystery 
of course but all is well that ends well I guess...  While I have the front 
panel off I think 
I'll use a little contact cleaner on the rest of the switches etc. They don't 
look "dirty" but should I clean and lube the gear train before replacing the 
front panel? Recommendations?

Ron K3PID