[R-390] New Subscriber with questions

[Paul H. Anderson]

On Sun, 3 Mar 2002, Tony Martin wrote:

> Greetings to all from a brand spanking new subscriber.
> I am the proud owner of an R390/URR, Collins, ser no.465.
> As you might imagine, I'm full of questions and eager to
> know and learn more about this wonderful receiver.

You made an excellent choice!

> First and foremost in my mind is the question regarding
> what is the normal way of dealing with the J108 balanced
> antenna input jack?  I have nothing like that in my inventory,
> in fact I don't even recall ever seeing anything that will
> mate with it (although obviously there is!).  Is there an
> adaptor (that is affordable) to adapt it to the standard
> PL259? 

There is an expensive adapter ($15-$30 depending) - a UG-970 and UG-971
(one goes to PL259, the other to "C"? from memory).  There is an IBM
network cable twinax adapter that works, that you can use to make one,
too.

> Was there/is there a cabinet enclosure for the R390 or is
> rack mounting the only way to go?  This one has the dust
> cover on the top, etc...no feet on cabinet...(suggestions)?

CY-979 and CY-917, I think - both are fairly expensive.  I can dig out
details of an ~$120 enclosure that is a new model and will work, but may
not be best for long term use, as it doesn't have good cooling holes,
something your 390 6082 tubes won't enjoy.

> A quick check shows that all controls/meters work, and I am
> assuming, "as they should".  Are there any recommendations
> (initial DO's and DON'Ts for a newbie owner)?

Don't worry too much about the cabinet - the covers will keep the dust and
cats and kids out.  Don't worry about the radium in the meters - it is at
a level similar to old watches and clocks.  Just don't eat the insides and
you'll be fine (there are long threads on this every once in awhile).

Heat is a big, big problem on the 390.  The 6082 tubes bake the AF deck
badly.  While it works now, it is likely the first point of failure.  
There are 4 47 ohm resistors coming off the base of the 6082 tubes in the
AF deck, and 4 47 ohm resistors coming off the 26Z5W tubes (or the diodes)
in the power supply.  These should reasonably be replaced - folks here use
5 W replacements - I happened to have used 2W flameproof ones, and did ok.

There is a guy designing solid state replacements for the 6082 tubes.  I'm
not wild about solid state in a radio like this, but the chance to remove
that much heat has to be a good thing.

If your radio dies - first thing to check is the B+ jack on the side - if
it is more than 180+-5 volts, shut it down immediately and check the VFO
tube and the VR tube in the AF deck - if the filaments aren't working in
either of those, your 6082 tubes stop regulating and you get unregulated
300+ volts on B+, which may damage capacitors, resistors and tubes.  At
any rate, track down and fix the problem before exposing the radio to any
more unregulated B+ than absolutely necessary.

Other than the heat and poor voltage regulation, the design is robust -
there aren't really any parts that will lead to some horrible chain
reaction that will destroy the radio.  On the R-390A, with mechanical
filters, C-553 in the IF deck if it shorts will fry the expensive filters,
for example.

> While in the USAF, I never was fortunate enough to get the R390
> at my "position", although they began arriving shortly before
> I got out (1961).  So it has taken 40+ years for me to "UPGRADE"
> from the beloved SP-600, but I finally made it! 8-)

Tbanks for serving, sir!

> I look forward to reading and learning more about the 390 now
> that I have subscribed to this group.  

This is a great group - they get kinda noisy sometimes, but the level of
experience is just amazing.  Do spend time searching the archives at
qth.net - there is a treasure trove of information, including all of what
I've said in this message...

> Thanks to all for your suggestions and patience.


Good luck with your new 390!  It is a beautiful radio, and well worth your
time and patience taking care of and using it!

I'm restoring an R-391, which is very similar to the 390, but includes an
8 channel autotune.  It is a lot of fun, because I just got it working
reasonably well - still need to align it, and fix the line level meter,
though.

Paul Anderson