[R-390] For the r-390 wishlist -- Things for the R-390/URR

[Barry Hauser]

Hi Tom & Gang

I have a few R-390's and R-391's.  They all work - mostly.  The only repair 
experience I've had was with one of the last R-390's out of Fair Radio. 
Dave, who used to work there back then and the R-390 resident expert, had 
kept it on his bench, tweaking it here and there and burning it in for a few 
weeks before shipping it.  When I got it, it was DOA.

The problem was an oddball one -- not dissimilar from your function switch 
experience on the R-390A.  Someone mentioned some other situation that was 
similar - wire pinched by the IF deck or something like that.

The R-390 has a big cable bundle running across the bottom of the mainframe. 
Where it crosses part of it is a cutout where there should be a small 
retainer clip.  Sometimes they're missing.  That cable bundle runs into a 
big connector that plugs into the audio deck.  It's like the R-390A setup, 
only the R-390 has heavier coax.  I'm not sure what made me do it, but I 
opened up that connector -- backed off the shell.

Inside, the shield/braids of something like 12 or 13 cables are connected to 
a terminal in the connector by means of a piece of solid hookup wire.  I 
seem to remember it was #13.  May have some significance :-).  The hookup 
wire and solder glob around it was cracked through from stress. Even with 
the shell off, it wasn't obvious.

With or without that clip on the frame bottom, the cable bundle tends to sag 
and gets jostled when the receiver is set down or moved around.  A bottom 
cover would minimize the movement, but still allow some jostling.  While the 
bundle can shift, it's fairly stiff and puts quite a bit of stress on the 
connections inside the plug.  Yes, there is a strain relief on it, but these 
are often not tight enough as the rubber wrap tends to shrink.  Ground point 
for a lot of connections, so, if it fails it renders the rig inoperative. 
Short piece of hookup wire, soldering with a high wattage iron, shore up the 
strain relief and she's good to go.  It's also a good idea to replace that 
clip and make things tight with some electrical tape or whatever.

The only other things I know come from Dave Medley's notes -- like replacing 
the 47 ohm resistors, etc. -- and how to solid state the voltage regulator 
to eliminate the heat from the 6082's, though a muffin fan is another 
solution.

I suspect many R-390's haven't needed the kind of intensive repair and 
pre-emptive PM applied to R-390A's, as they were of an earlier, more 
expensive, more proven design, and, as Les Locklear likes to quote, "a man's 
radio".  That said, perhaps the most important tips are to 1. wear the 
correct (not politically correct) after shave, 2. but don't shave for a few 
days and work up a good sweat (so as to exude some manliness), 3. consume 
compatible beverages (like regular, like Southern Comfort, Jim Beam, etc., 
but not light beer or Tanqueray and so on. (If you go with 180 proof rum, or 
vodka, you can also use it to clean the gear train -- and if you want to 
truly prove your manliness and bond with the radio, you can imbibe some of 
the gear train drippings).  An ailing R-390 will generally perk up and work, 
purely out of mutual respect, even with a couple of weak tubes and crispened 
resistors.

Don't know if all that really works, but does improve one's general 
orientation and attitude before approaching the project.

Barry


Tom wrote:
Since Dave Medley retired, we've only see a few bits here and there on
the R-390 vs the 390A.  Anyone able to add any 390 experience?

I've only recently dug into any R-390's.  The 390A I can almost tear
down and put together blindfolded* - though I'm not sure I can add
anything that hasn't been covered in "Pearls"
Other than the one odd troubleshooting incident written about earlier,
I've not ran into many things that weren't simple by-the-book fixes.

Reason I ask about the R-390 is I have 2 here that don't seem to have
simple by-the-book problems. (they'll get back up on the bench
eventually)