[R-390] R-390A trouble (I FOUND THE PROBLEM)

Fri, 29 Mar 2002 11:00:31 -0500

Ah, yessss.  Close eyeball inspection (with tapping, now add wiggling) wins
again!  What did I tell ya'?

This is a variant on the classic "dumb problem" -- looks like it's
connected, but not so.  Same idea as the broken ground tie point I found in
a non-A audio deck connector shell a while back, and similar to bad mini-bnc
jumpers, etc.  "Dumb", yet calling for a sharp, forensic eye and a
safe-cracker's touch.

However, the mystery is not solved.  We're not out of the woods yet.  Why
only over 3 MC's?

I suppose it's possible that as things heated up, the gap in the socket pin
expanded then oxidized and developed some capacitance or whatever.

Let's see what happens when you fix the socket and burn 'er in.

Barry

> After wiggling almost all the leads to confirm security, I discovered the
> following.....
>
> Pin 5 of V201/6DC6, from the underside, seemed to be in place and secure.
> Upon wiggling, it seemed loose, so I gently tugged on the pin lead and it
> came out of the socket from below the plastic.  It was broken between the
> socket pin and where it emerges from the socket mold on the bottom.
>
> Apparently, there was enough contact to do the initial alignment, and
after
> a couple of hours burn in, it insulated itself, creating the below
symptoms.
>
> What was maddening was that the break was within the plastic mold of pin
5,
> which took a tug to break it from the plastic.  Three components are
> attached.  Later I will summarize what was affected and the fix.
>
> WOW......this is one for the books.
>
> I think I will go for replacement, but if there is an easy fix, I will
> consider it.
>
> Well, thats it.  Thanks for the support and help with this problem.  After
I
> complete the repair, I will post a summary of the symptoms and fix.  So
long
> for now.
>
> Regards,
>
> Jim
> 73, KF4ICZ
>
> ----- Original Message -----
> From: "Jim Temple" <[email protected]>
> To: <[email protected]>
> Sent: Thursday, March 28, 2002 10:56 PM
> Subject: Re: [R-390] R-390A trouble
>
>
> > 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" <[email protected]>
> > To: <[email protected]>; "Jim Temple" <[email protected]>;
> > <[email protected]>
> > 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
> > > [email protected]
> > > http://mailman.qth.net/mailman/listinfo/r-390
> > >
> >
>
>
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