[R-390] r-390a chirping CW

[Michael Murphy]

I wonder if the chirping R390A fixes bona fide chirp by undoing it?
De-Chirping in effect. Of course the chirp would have to be going in the
right direction - like upper side chirp and lower side chirp.

MM


----- Original Message -----
From: <JMILLER1706 at cfl.rr.com>
To: <r-390 at mailman.qth.net>
Sent: Monday, June 14, 2004 3:39 PM
Subject: Fwd: Re: [R-390] r-390a chirping CW


> This has taken on an interest to me because I have two 390a's here, one is
a Stewart-Warner, the other a Collins (almost).  I notice a very slight
"chirp" barely noticable in the SW as AGC changes.  However, it was much
more noticable in the Collins until I changed a mixer tube, ...it is
lessened, but still noticable, maybe a tad more than the SW now (judging by
ear).  My theory was that the AGC was pulling on a mixer tube, which then
pulled more on one of the oscillators causing it to "chirp".  Changing the
tube reduced it.  I also observed the +250 volt line which drives the xtal
oscillators and other stages, and noted a moderate change in its level as
AGC changed (a change in AGC would cause all controlled tubes to pull a
varying plate load from that line).  The 250V line in both radios seemed to
pull the same amount, but the Collins still show a little more "chirp" as
AGC changed.  I would guess by ear to be 20-40 Hz.  Is this normal?  Would
be interesting to hear from ot
>
> hers... turn your BFO onto a strong, stable signal and run RF Gain up and
down. ... you may notice a slight pulling in beat note.  Do others note this
also?
>
> ----- Original Message -----
> From: Forrest Myers <femyers at attglobal.net>
> Date: Monday, June 14, 2004 8:04 am
> Subject: Re: [R-390] r-390a chirping CW
>
> > Hello James,
> > I checked the 150 volt line with my Fluke DMM and it seems to be very
> > stable. Will check it more closely with my old analog VTVM and see
> > how it
> > looks.
> > Thanks for the help.
> >
> > Later,
> > Forrest
>


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