[R-390] R-390 Woes

Barry n4buq at knology.net
Wed Oct 8 13:39:55 EDT 2025 

Adam, 

Okay. Please keep us posted if you do decide to do that. I see where it appears to be a mix of surface mount and through hole components. I can still do surface mount but it can be a bit more of a challenge. 

I do okay with SSB and the envelope detector but at one time, I had an add-on PD for an R390A that I had at the time and it was kind of nice. Of course, I could always feed the diode load out to a radio that can receive the IF and listen to it that way as well. 

Good luck with it, 
Barry - N4BUQ 

> Barry,

> I was going to try my hand at putting them together and getting them working. If
> I can pull that off, I'd be more than happy to help the R390 community out,
> probably for the cost of the board and components, which isn't too bad.

> This is just a college hobby of mine, not looking to sell anything :)

> On Wed, Oct 8, 2025, 13:27 Barry < [ mailto:n4buq at knology.net |
> n4buq at knology.net ] > wrote:

>> Adam,

>> What did you plan to do with those boards? I might be interested in one if
>> available.

>> Thanks,
>> Barry - N4BUQ

>> > The only mod I had planned was using a Treetop Circuit SSB board. I had
>> > ordered boards from PCB express using TTC's design and was going to try to
>> > piece one together, and when I picked up this R390 it came with one that
>> > was never installed.

>> > The mod doesn't seem to work very well, let me take a closer look and see
>> > if I can notice any mistakes, now that I have the documentation for it! I
>> > appreciate it sir.

>> > Adam

>>> On Wed, Oct 8, 2025 at 12:06 PM Jacques Fortin < [ mailto:jacques.f at videotron.ca
>> > | jacques.f at videotron.ca ] >
>> > wrote:

>> >> 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 : [ mailto:r-390-bounces at mailman.qth.net | r-390-bounces at mailman.qth.net ] <
>>>> [ mailto: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 < [ mailto:jacques.f at videotron.ca | jacques.f at videotron.ca ]
>> >> >
>>>> Cc : R-390 Mailing List < [ mailto:r-390 at mailman.qth.net | 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 < [ mailto:jacques.f at videotron.ca |
>> >> 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 : [ mailto:r-390-bounces at mailman.qth.net | r-390-bounces at mailman.qth.net ] <
>> >> > [ mailto: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 < [ mailto:r-390 at mailman.qth.net | 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 |
>> >> > 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 < [ mailto:morehouse90 at gmail.com |
>> >> > 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







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