[R-390] r390, not the a, audio problem, possibloe agc problem

Thu, 13 Feb 2003 11:50:03 -0800

(1) Check jumper is installed across TB101 pins 14-15.

(2) I would suspect a leaky C528 (0.22 mfd) or C527(0.047 mfd) capacitor.
But any open resistors around V507 or V510 could cause the problem.

(3) If you can loop a small wire around pin 6 of V507, then reinstall the
tube, you should see B+ voltage at this point when the limiter switch is
off.  It should go to zero when the limiter switch is on.  If you don't see
B+, either C528 or C527 is leaky, or R543 or R541 is open.  You can use the
same test with pin 1 of V510 to gain more information.

Does the limiter work when it is switched on?  C102 (0.22mfd) is sitting in
front of the limiter control.  Obviously audio is getting through, but are
there any other symptoms?

73 de Bill, AB6MT
[email protected]

----- Original Message -----
From: "KC8OPP Roger S." <[email protected]>
To: "James Bischof" <[email protected]>
Cc: <[email protected]>
Sent: Thursday, February 13, 2003 2:29 AM
Subject: Re: [R-390] r390, not the a, audio problem, possibloe agc problem

> James,
>
> I had the exact same problem here with one of my
> R390's.  But I never determined what the problem was.
> During trouble shooting and alignment I noticed the
> problem and put it on the list of things to work on, a
> long list for this particular radio.  As time went by,
> the problem diminished and finally disappeared all
> together.  The only thing I did was keep the radio on
> and operating.
>
> Now after 2 years, there is no evidence of the
> problem, although I know it is lurking in the
> background.  This is a mostly Motorola set and I leave
> it on 24/7 as part of my AM station.
>
> Sorry I don't have a solution for you, but I would be
> interested in what you find out.  In the mean time,
> plug it in and let it play.  Could work for you too.
>
> 73's
> Roger
> KC8OPP
>
> --- James Bischof <[email protected]> wrote:
> > I have two Junker r30, not the a,  and am trying to
> > make one good one. I spent all day Saturday and
> > Sunday  and I finally got one to work!  My problem
> > is this, I have to turn the limiter on to hear the
> > stations. Radio seems to work pretty good. When I
> > turn the limiter off the carrier level is  not
> > affected. When the limiter is off I can hardly hear
> > any audio, but I do hear some ac hum.   I do not
> > think it is in the if chassis or power supply
> > module. I did sub the audio chassis with out any
> > luck. I think it might be in the rf deck, but I
> > don't exactly know why I think this. I was also
> > thinking I might have a agc problem. Any help
> > please.
> > James Bischof
> > Schenectady, New York
> > Wa2qin
> >
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