[R-390] R-390 Woes

[Jacques Fortin]

Hi Adam,
No need for an "original" BFO switch.
As the W3JHR mod. used a DPDT one, and if it is still fitted there, only half of it can be used as a BFO power sw.
Check how the V508 socket is wired in your IF deck: that should confirm that it was modified to use a 6BE6.
You can also keep the mod. in place (if it works) unless you want to have an "original" R-390, meaning without a product demodulator fitted in. 

73, Jacques, VE2JFE in Montreal

-----Message d'origine-----
De : r-390-bounces at mailman.qth.net <r-390-bounces at mailman.qth.net> De la part de Adam Morehouse
Envoyé : 8 octobre 2025 11:53
À : Jacques Fortin <jacques.f at videotron.ca>
Cc : R-390 Mailing List <r-390 at mailman.qth.net>
Objet : Re: [R-390] R-390 Woes

Well that's interesting, I guess I'll need to find an original BFO switch.
No wonder the thing didn't work, there are no substituted tubes in it. Now I get to figure out how to undo all of this.

:(

On Wed, Oct 8, 2025, 10:18 Jacques Fortin <jacques.f at videotron.ca> wrote:

> Hi Adam,
>
> I think I recognise this mod., the clue being the 56k resistor in the 
> picture.
>
> See attached doc.
>
> If it is really the original W3JHR mod. that was implemented there, 
> the BFO on/off switch has been also changed for a DPDT version 
> (switching the audio input between the AM and product detectors and 
> powering the BFO oscillator at the same time).
>
> If it is that, the BFO tube (V508) have to be a 6BE6/5750 instead of a 
> 6BA6/5749…
>
> This is basically the same product detector that I use in my own R-390 
> and R-390As, by using a changeover relay inside the IF deck instead of 
> using a substitute BFO switch.
>
> See also the W7DI type of implementation attached.
>
> Larry Haney also worked around this theme and used a 6BY6 tube for the 
> product detector because it works better than a 6BE6 in the same 
> configuration.
>
> I also worked with Larry to find a way to still use the noise limiter 
> in the SSB mode, but the result of our experiments are not final, and 
> the AGC modifications we devised to “improve” the R-390 / 390A are 
> still not fully tested.
>
> Stay tuned, I should have time to re-visit that during the next winter.
>
>
>
> 73, Jacques, VE2JFE in Montreal
>
>
>
> -----Message d'origine-----
> De : r-390-bounces at mailman.qth.net <r-390-bounces at mailman.qth.net> De 
> la part de Adam Morehouse Envoyé : 8 octobre 2025 03:44 À : R-390 
> Mailing List <r-390 at mailman.qth.net> Objet : Re: [R-390] R-390 Woes
>
>
>
> I might have found the issue.
>
>
>
> Can anyone tell me if the white coax in the follow pictures is supposed to
> be there?
>
>
>
> https://photos.app.goo.gl/M6Qcr9mXFrZ6sgiRA
>
>
>
> It doesn't look original to me, nor does the the resistors and caps in
> front of the BFO. They seem to be hooked to V508 and RT512.
>
>
>
>
>
>
>
>
>
> On Tue, Oct 7, 2025, 16:55 Adam Morehouse <morehouse90 at gmail.com> wrote:
>
>
>
> > Hey guys,
>
> >
>
> > I appreciate the pointers on my R-392, and now that it's buttoned up,
>
> > it's time to work on my R-390. I only tested this briefly when I first
>
> > got it, today I threw it up on the bench. Supposedly this was restored
>
> > by Rick Mish, it is very clean (except the gear train, which has a lot
>
> > of fresh grease...), and the front panel is pristine.
>
> >
>
> > It does pull stations, but the volume is extremely low in AGC mode,
>
> > and gets slightly louder when placed into MGC.
>
> >
>
> > In MGC, with the BFO switched on, it plays at a normal (not super
>
> > loud, but loud) volume.
>
> > In AGC, with the BFO switched on, it hums, low volume audio.
>
> >
>
> > The limiter seems to have no effect, and varying the BFO doesn't do
>
> > anything at all no matter AGC/MGC.
>
> >
>
> > I have Tom's solid state kit installed, and B+ at the AF deck test
>
> > point is a steady 180.5vdc.
>
> >
>
> > I am going to dig out the TM's later on, I have them somewhere...but
>
> > maybe somebody here can help point me in the right direction.
>
> >
>
> > Thanks!
>
> >
>
> > Adam K2AAM
>
> >
>
> >
>
> >
>
> ______________________________________________________________
>
> R-390 mailing list
>
> Home: http://mailman.qth.net/mailman/listinfo/r-390
>
> Help: http://mailman.qth.net/mmfaq.htm
>
> Post: mailto:R-390 at mailman.qth.net <R-390 at mailman.qth.net>
>
>
>
> This list hosted by: http://www.qsl.net
>
> Please help support this email list: http://www.qsl.net/donate.html
>
______________________________________________________________
R-390 mailing list
Home: http://mailman.qth.net/mailman/listinfo/r-390
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:R-390 at mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html