[R-390] New 390A owner & fan

[Barry Hauser]

Hi Andy & Welcome to the '390 Asylum ;-)
>
> Having recently realised a long ambition to own a R390A receiver I have
> become a subscriber to this list and I gather that you guys  like to know
> some details on "new found" sets.

Yes -- as a rule, we're very nosy about other folk's '390's.  Eventually
we'll have live web cams running 24/7 with multiple channels with channels
like -- Newly arriving '390's being unpacked (suspense), Full-Blown
Recapping (intense) , Full Gear-Train Teardown, Cleaning & Reassembly
(higher intensity), Mechanical Synch and full Electronic Alignment
(cerebral), Panel & Knob Refinishing (fine arts 'n crafts), Modifications
(horror), Demodification (redemption), Actual Reception Performance
(sports), and so on ....

> It is a Motorola built one from order 14 - PH - 56 serial No 564.  It has
a
> screen-printed front panel in excellent condition and the whole set is
> pretty clean and shiny for going on 50 years old.

Just don't compare it to the inside of that PC you bought six months ago.
They catch more dust than those HEPA air filters.

  Both meters are originals
> and the set has top and bottom covers but these look so new and un-marked
> that I suspect they are repros.

Probably.  Most originals are either (a) missing or (b) dented and scratched
with some smashed in louvers.

  The PTO is a Collins and most of the
> sub-assemblies are stamped MFP which I assume is Motorola.

That's Mildew-Fungus Protection, or Moisture-Fungus-Protection.  Someone
just called it "greenish".  Usually more yellowish or golden in color.  If
any is flaking (unlikely), be careful not to ingest it as it contains
mercury and possibly other bad stuff.  Perfectly safe in place.  It does
become a bit of a problem if you have to do any soldering as it has to be
scraped away from the joints before proceeding.

> Five of the tubes have IERC cans but mostly it has original silver ones.
It
> still has both rectifier tubes and the RT501 barretter is in place.  There
> is no diode load jack.

Some of  the silver ones aren't so bad -- pull a few and check them.  I've
found some retrofitted with black heat sink inserts, usually of the
"accordion fold" or pleated type.  If so, they're nearly as good as IERC
shields.  On the other hand, I just got a Stewart Warner which has all IERC
shields, but someone made off with the inserts.

>
> It has some mods by a previous owner,  the BFO V505 has been replaced with
a
> 6BE6 to make a product detector which I guess follows one of the
well-known
> mods to do this.  Also, the unbalanced antenna connector has been replaced
> with an SO239 which I should be able to replace with the proper C type.

I suppose, if you want to be a purist.  You might just locate a C-type panel
connector and keep it close by.  The SO239 is more convenient.

 The
> balanced twin connector is still on pushed-in wires though as the proper
> plug is unobtainable here.  The cover that goes over the crystal
oscillator
> subchassis is missing.

You should be able to find them easily -- they are "twinax" connectors
commonly used in IBM-type networking (token ring?).  They are usually
available new and cheap as most networking has gone 10-base and 100-base-T
which is twisted pair with modular (telephone style) plastic plugs.  You can
also find an adapter that goes from twinax to C or something else.  These
have one side of the pair grounded internally.  Might be able to get one
from Fair Radio or watch the "e-place".

>
> Haven't had the chance yet to look deep inside to see what's been replaced
> but  it was demonstrated working before I bought it so functionally I know
> that it's basically OK.   Functionally, everything seems to work.

Even so, pull the IF deck and look "under the bonnet".  Hopefully you have a
spline wrench to unfasten the two clamps on the controls.  You should check
C553 (I think) -- that's the mechanical filter killer, should it short out.
We routinely replace those with a new orange drop or other new manufacture
cap as a preventative.  There are clear photos on Chuck Ripple's web site
http://www.r390a.com/ProbCaps.html

Also be sure to visit Al Tirevold's web site
http://www.r-390a.net/faq-refs.htm

The audio deck is easy to pull.  Check for a leaked out 8 mfd metal tantalum
cap, usually with a nasty blemish on the mounting board.  This can be
replaced with a 10 mfd electrolytic.  If it has not yet spilled its acid
guts, best to pre-empt that.

>
> Question:
> It has only a single fuse holder on the rear panel which I think is
correct
> for this serial number but if the additional B+ fuses were worth fitting
in
> production, should I add them to my back panel like the factory or hide
them
> internally? Or not bother?

There is some value to the added fuses (one is for filament).  An overload
on the B+ will blow the 1/8th amp fuse much sooner than the line fuse, which
might not blow until after collateral damage occurs.  Frankly, though, I
have no idea how often this may happen.  If you are going to retrofit, it
might make more sense to fit the proper fuse holders to the back panel,
using some of the drawings (Y2K manual, etc.) to position them.  The correct
way is to use a "Greenlee Punch" which has the correct "D" shape or circle
with a flat on one side.  This keeps the fuseholder from rotating in the
panel.  If not, then improvise or make sure you get the fuseholders with the
large starwashers which bite into the rear surface and perhaps secure with a
drop of epoxy or something.

Internal fuseholders would be more convenient and keep the back panel
"authentic" to the version, however, I haven't found any that were very
confidence inspiring.  Tempted to use the inline type often used in
automotive installations, but I don't think they're rated for high voltages.
>
> 73 to all, and happy Independence Day to our friends on the other side of
> the pond.

Well, thank you very much, Andy.  Very sporting, all things considered.
(Imagine if someone told King George III that one of his subjects would be
conferring greetings on the dual occasion of the anniversary of the
(declared) independence of the colony and his receipt of an American-made
radio receiver.  Well, maybe he wouldn't feel so bad if he also knew how
much Racal stuff we've got here ;-)

Best of luck with 'er -- and enjoy!

Barry