[Swan] Swan 350 & 500cx AGC Problem

[Ken, WA2LBI]

Bob,

Thanks for the response. My 500cx manual also specifies setting the RF gain at 3
O'clock for reception. That doesn't solve the problem. It still has to be
turned down further on very strong signals and then up again for weaker
signals. It just seems the AGC circuit isn't developing the proper voltage to
control the gain.

Does anybody have the voltages for various points in these rigs that they could
share with the group? It would be especially useful to know what the voltage is
at various points in the receiver for a given signal generator input level.
Does anybody have these scribbled on their working copy of the schematic?

The previous posts regarding high signal level distortion on either of these
rigs may have appeared before I joined the reflector so I would appreciate
hearing from any of the Swan "wizards" who have tackled this problem (and
won!).

Thanks,

Ken, WA2LBI
wa2lbi@arrl.net

Quoting Bob or Chris Balonis <rmborcmb@penn.com>:

> Don, Ken,
>
> I had noticed that the manual for the 350 suggests setting the RF gain to
> the 3 O'clock position as part of the original receive operational set-up.
> I believe it has been mentions previously on the reflector (Stu, I think)
> that distortion on very high signal level was "normal," and that is why the
> manual specifies 3 O'clock setting.  My 350 also has some small amount of
> distortion on high signal levels.
>
> Happy Holidays to all!
>
> Regards, Bob
>
> ----- Original Message -----
> From: "Ken, WA2LBI" <wa2lbi@frontiernet.net>
> To: "Don Flenner" <w4ych@earthlink.net>
> Cc: <swan@mailman.qth.net>
> Sent: Thursday, December 18, 2003 9:28 AM
> Subject: [Swan] Swan 350 & 500cx AGC Problem
>
>
> > Don,
> >
> > I have a 500cx that reacts in the same manner. I also believe it is an
> AGC/ALC
> > issue but have been unable to locate/correct it. I had recapped and
> changed a
> > number of resistors in this rig a while ago and that corrected the ALC
> problem
> > (my xmit audio was distorting on peaks). It would be helpful if the
> schematic
> > had expected voltages printed at various points to allow for comparison.
> >
> > Has anybody come across a similar problem in the 500cx (or 350) and found
> a
> > remedy?
> >
> > Thanks,
> >
> > Ken, WA2LBI
> > wa2lbi@arrl.net
> >
> > Quoting Don Flenner <w4ych@earthlink.net>:
> >
> > > Greetings All,
> > >
> > > I picked up a 350 a couple months ago and have a question concerning
> audio
> > > distortion on strong signals. The receiver is very hot, maybe to hot. I
> > > would think that the problem is in the AVC/AGC circuit but I can see
> > > anything wrong and resistance checks seem to be in the ball park. I have
> > > noticed that when I back down the RF gain control the audio quality is
> > > better. I was told that the AGC system is kind of unique, true or false?
> > >
> > > The rig is in very nice cosmetic condition and I have re-capped the
> power
> > > supply. It would be a keeper if I can get the audio squared away....
> > >
> > > Any thoughts and guidance would be appreciated.
> > >
> > > 73,
> > > Don, W4YCH