[R-390] R-390A trouble

[Glenn Little]

Jim

What type of capacitor did you use for he replacement?  Was it black in 
color?

Save yourself a lot of headaches and time.  Replace all of the capacitors 
like this with a modern poly type capacitor.  One that is highly 
recommended is the orange drop.  It is rather expensive by a very good 
performer.  The capacitors of 50 years ago,were good in their day, but they 
have seen too many birthdays.  If the one you put in was not leaky (did you 
check leakage?) it will be leaky soon.  All black beauties are bad by 
definition.  A wholesale replacement of these goes against the purist, but 
is the best way to repair a radio of this vintage and keep it repaired.

If you like pulling the radio out of the rack/cabinet, clearing the work 
bench, getting the test equipment warmed up, heating the soldering iron, 
cussing the way this and that are installed, removing a module and 
troubleshooting it, realigning the radio and then putting it back into the 
rack/cabinet, then by all means find the bad capacitor and replace only 
that part.

If you want to enjoy using the radio, get the radio onto the bench and 
spend a little time replacing ALL of the black beauties in the radio. Then 
realign the radio once. After you put it back into the rack/cabinet, you 
should now be able to enjoy the radio for many years to come without having 
to work on it many times.

If you should find a good black beauty, frame it because it will not stay 
good for long.  They all leak, some worse than others.  If you do not 
replace the killer capacitor, look forward to replacing the mechanical 
filters.  The capacitor is cheap in comparison to the filters, if you can 
find someone to sell you a filter.

The choice is yours.  Do a complete capacitor replacement and enjoy the 
radio, or replace the capacitor when they fail bad enough for you to tell 
by the way the radio performs and engoy the radio for a period of time 
until it fails again.  And it will continue to fail until ALL of the black 
beauties have been replaced with a quality capacitor.

Wishing you happy listening after the capacitor replacements.

73
Glenn
WB4UIV

   At 10:56 PM 3/28/02 -0500, Jim Temple wrote:
>OK, I replaced C227 .047.  The old one measured .075 when out of circuit.  I
>have a picked-over RF parts deck that happend to have this cap.  It measured
>.04745, so hopefully this is the problem.
>
>HOWEVER, I am going to clean, inspect, wiggle, tap, eyeball, and generally
>give it the twice over before reinstalling in the morning.  I'm winding down
>for the night.
>
>Will report back after reinstallation of the RF deck in the morning.
>
>Thanks for the great support and suggestions.  Good night.
>
>Regards,
>
>Jim
>73, KF4ICZ
>
>----- Original Message -----
>From: "Barry Hauser" <barry@hausernet.com>
>To: <bill@iaxs.net>; "Jim Temple" <jetemp@insightbb.com>;
><r-390@mailman.qth.net>
>Sent: Thursday, March 28, 2002 9:55 PM
>Subject: Re: [R-390] R-390A trouble
>
>
> > > Barry, I think you've got it.
> > >
> > > But I thought of another thing to try. Because the set is
> > > oscillating within itself, something common to the IF and
> > > RF decks is carrying energy between them.
> > <snipped>
> >
> > Got what?  I dunno, but, hey, Bill, I think YOU"RE onto something.  Jim
> > should check out all those jumpers with the mini-BNC's -- maybe one of 'em
> > was swapped with that Skyhighgain cable Norman told us about.
> >
> > Seriously, tho' -- wasn't that another thing that could cause weird
> > problems -- bad mini-coax?
> >
> > When the rational, logical, informed, incisive, deductive approach fails
>...
> > Well, let's consider ALL the clues ...
> >
> > Squeal -- loud disturbing noise, alarm, or (sl.) to give information, to
> > "rat" on.
> > Happens over 3 MC's, that could be written as >3.  Looks like a bird,
>don't
> > it?
> > Motorboating, boats, water, ocean -- could be a seagull, or maybe
> > "putt-putt" = golf
> > Then there's the thing about cats.  Wait a minute!  A bird that looks like
>a
> > rat is a bat -- but then what's golf got to do with it?  This is going
> > nowhere -- might mean something to a witch.  Is Les around?
> >
> > Forget all that -- pull the RF deck and check it out.  Could be an
> > "underneath-ARGHHH-do-I-hafta?" problem.  Give it the close eyeball
> > inspection.  By all means CLEAN the bandswitch -- twice. (unless I missed
> > something and you did that already)
> >
> > Nobody seems to be focused on the >3 thing.  Why would this problem kick
>in
> > there?  What is different circuitry-wise about 0-1-2-3 vs 4+?  I guess one
> > thing might be a rotor section or two on the bandswitch, no?  Maybe not.
> > Any particular reason a bad cap would cause the squeal and motorboating to
> > start at 4 MC's?
> >
> > Great, now I'm gonna be up all night 'cause of somebody else's radio.
> >
> > Barry
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> > _______________________________________________
> > R-390 mailing list
> > R-390@mailman.qth.net
> > http://mailman.qth.net/mailman/listinfo/r-390
> >
>
>
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Glenn Little                         glittle@awod.com   QCWA  LM 28417
Amateur Callsign:  WB4UIV            wb4uiv@amsat.org   AMSAT LM 2178
QTH:  Goose Creek, SC USA (EM92xx)                      ARRL  TAPR
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