[R-390] R-390 Woes

Wed Oct 8 13:27:23 EDT 2025

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 <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 : 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
>> >
>> > >
>> >
>> > >
>> >
>> > >
>> >
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