For R390A Owners

[xe1yzy]

Just a tip for share...

My R390A had an annoing  noise, ( the same that you can hear on your receiver when turns on a lamp, or the the XYL turns on the blender in the kitchen), I try to locate the origin of those "sparks" inside the rig many times, and I can't found it, until the yestarday when the ON/OFF Micro switch dosen´t turns off the receiver anymore, and the rig keeps on.

When I check this tiny switch, first feels  very hot, and have several omhs between the terminals, I dosen´t have a replace part on hand, so I just simple tie together the on/off wires, and make another smoke test, Voila! not only the noise  disaper, also the receiver works better!

RGDS!

Pedro

[ke7trp]

This explains why my R390A does not fully turn off.  In the off postion the lamps are all still lit. 

Thanks Pedro.

Clark

[W1VD]

Fair Radio has NOS replacement micro switches. Bought mine on epay a year or so back.

[WQ9E]

I also had to replace my 390A switch several years ago; they seem to fail pretty regularly.  In some cases, you might consider adding an inrush current limiter to the AC mains and perhaps a "snubber" (capacitor and resistor in series across the contacts) to protect the switch.

I have gotten into the habit of using power strips for my vintage gear that gets used a lot to save the power switches since many of them have switches that are difficult to get and replace.  Both the Drake 4 and 7 line gear also commonly have switch issues and I replaced the switches on both my R-4 and R-4A before I went to outlet strips; ditto for my SB-102 but I have owned it since I got my general in 1975 so it did provide a long life.  Now I just leave the gear turned on and kill the power with the strip.  Several years ago someone's station photo in ER showed custom consoles with toggle switch controlled outlets for the gear and it looked like a very neat job.

The outlet strip also works well for gear that has associated equipment used with it; a couple of times I realized I had neglected to turn off a couple of my RME preselectors when I switched off the associated receiver.  So it also helps with operator mental error.

You can often find the outlet strips for a few dollars at the big box stores. When none of the radios are in use, the breaker panel that feeds them is killed by a shutoff switch.  If I left power to them all of the time I think I would spring for the better quality metal cased outlet strips; the quality of some of the plastic ones is pretty questionable.  One of my colleagues unplugged his laptop power supply from one earlier this week and part of the guts of the strip came out along with plenty of sparks.  It woke him up a whole lot faster than a Venti Latte from Starbucks.

[Todd, KA1KAQ]

These switches are notorious for welding together over time. Along with the outlet strip approach, some have added soft start MOVs in hopes of lessening the initial *snap*, though I'd think it wouldn't make a lot of difference until after the circuit was completed by the switch.

The KWM-2s were notorious for this as well, Oak being the company that supplied the originals. I've been fortunate to escape this issue so far, but this thread is a good wake up call that it's never too late to lay in some spares.