[R-390] Various R390 issues

[Bill Smith]

> Hello all, and thanks in advance for the help!  I have some more questions
> on the R390A:
>
> 1. I have seen many of you write up the use of Orange Drop caps to replace
> the Vitamin Q, etc., paper stuff.  These caps have radial leads.  In the
> Allied catalog is a vendor called ASC which offers axial-lead 400V
> metallized polypropylene caps with full temp rating at 105 degrees C.  Any
> reason why I couldn't use these as alternatives to the Orange Drops?  A
0.1
> mfd 400 V cap is 0.328 diameter x 0.813 length...would seem like a pretty
> good fit, but before I fall off the table and run down that path I was
> wondering what the rest of you thought.

First, are you sure the Vitamin Q's are bad?  The VitQ caps in the R-390
here appear to be in excellent condition.  Just ran across a can of Vitamin
Q parts, NOS, but don't yet know the values, etc.

Regarding the caps you located, they sound great.  I get similar caps from
Bob's Antique Radios, though apparently they are made in Taiwan.  Some
people prefer all-American.

>
> 2. I have a case of sticking meters.  They are original equipment.  I have
> read that the original meters have radioactive material in them.

I don't think all do, but if the needle and scales look "orange" or "burned"
they are radioactive.

>Is it a coating on the needle to make it read in the dark, or ???

Yes, the needle and scale markings used to glow green.  The phosphor is long
spent, but the radium used to excite the phosphor is still quite active and
will be for the next 20,000 or so years.


>Is it possible to disassemble the meters to correct the sticking?  Any
other suggestions here?

Meters in general can be disassembled, and, with thin strips of adhesive
tape, particles in the meter movement can be removed to eliminate sticking.
The R-390 meters can be disassembled but you need to be very cautious that
you don't inhale any dust or material from inside the meter.

>
> 3. Other than cosmetics, is there any particular reason why I should rebui
ld
> the large electrolytics?

Not sure which you are talking about.  The power supply is probably ok (big
oil-filled 4mfd or so cap).  The AVC capacitors (2 x 0.1 mfd) are also oil,
and have a high failure rate.  I have rebuilt one of mine by gutting it and
placing a 0.22 mfd polyester mylar inside.  The other rests disconnected.

>I am considering building an assembly to plug in
> in place of the caps, but it won't be a pair of round cylinders (so there
> will be a bit more room to work).  Comments or suggestions here?

Not sure why you need a plug-in assembly.

>
> 4. What kind of connectors are used on the coax cables between modules?
> Looks like an anemic BNC (grin).  Reason I ask is that the insulation has
> cracked on a couple of the coax cables going to the IF assembly, and I see
> some repair work in the future (sigh).

Think the best bet is to recover and reuse the old connectors.  They are
hard to find.

>
> Thanks again for the help and advice.  It's a wonderful receiver, and
works
> great with my
> Valiant II.
>
> Dave Maples, WB4FUR
>
There are others who are much better equipped to advise you than I, hope
they leave comments.

73 de Bill, AB6MT
billsmith@ispwest.com