[R-390] r-390a chirping CW

[James Miller]

Another thought:  Check to be sure the 150V regulator tube is firing (it's
mounted on the audio module).  If the VR tube is bad, the 150V line may not
be held constant, and changing AGC could cause it to change as the tubes
pull more/less current.  I think the BFO (and maybe the PTO) is run off the
150 vold line, so if it's changing a lot the BFO would tend to "chirp".  Put
a VTVM on the 159 line and watch it......

----- Original Message ----- 
From: "Jordan Arndt" <jordana at nucleus.com>
To: "James Miller" <JMILLER1706 at cfl.rr.com>
Sent: Sunday, June 13, 2004 7:13 PM
Subject: Re: [R-390] r-390a chirping CW


> I;d check the voltage to the CW Oscillator tube...specifically the B+ and
the
> screen voltage at the tube... perhaps the dropping resistors have risen in
> value... 73 de Jordan...
>
> James Miller wrote:
>
> > I have found that replacing the first and/or second mixer tube may help
the
> > chirp.  Changing AGC on the mixer seems to cause it to load down th
> > oscillators as the AGC increases, pulling them off frequency slightly.
Also
> > could be another suspect tube, maybe an osc. tube.
> >
> > ----- Original Message -----
> > From: "Forrest Myers" <femyers at attglobal.net>
> > To: "r-390" <r-390 at mailman.qth.net>
> > Sent: Sunday, June 13, 2004 10:33 AM
> > Subject: [R-390] r-390a chirping CW
> >
> > > Hello,
> > >  I have a capehart r-390 a sn 557 that is working quite well except
for a
> > > couple of problems. All bands and all filters work. There are a couple
of
> > > problems though and I'm asking the learned group on this list for any
> > quick
> > > information or ideas.
> > >  Problem #1:
> > >   Good clean CW signals chirp when heard on the 390a. It sounds like
the
> > BFO
> > > changes frequency with AGC levels. Checking the voltage at the audio
> > module
> > > and it's a steady 150.1 volts. Haven't checked farther into it.
> > >
> > >  Problem #2:
> > >   Audio level is low but sounds good. I have to run the Local Gain
control
> > > wide open to get a comfortable listening level. This problem has crept
in
> > > over the past year. All tubes have been replaced. the radio has been
> > > re-capped, including the filter capacitors in the audio module. It has
> > been
> > > aligned and the PTO is very linear after setting the end points. The
rig
> > > works very well except for the above mentioned problems. I've been
away
> > for
> > > about 9 months and haven't used the rig. Am planning on getting into
it
> > > again after building a set of test wire extender so I can check into
> > > voltages and signals. Just thought I'd put out the symptoms to see
what
> > > advice I could gather.
> > >
> > > 73 DE AG4ND
> > > Forrest Myers
> > > -------------------------------------------------------------------
> > > "Security is mostly a superstition.  It does not exist in nature...
> > > Life is either a daring adventure or nothing."  -- Helen Keller
> > > -------------------------------------------------------------------
> > >
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