Jerry, Because I found many different 'specs' for the oscillator voltages in the A, I wrote a doc about it. The 390 voltages should be very similar to the 390As in my doc: R390A Oscillator Output Level Affects <https://www.r-390a.net/R390A%20Oscillator%20Output%20Level%20Affects.pdf> .
Regards, Larry On Wed, Nov 6, 2024 at 2:50 PM <[email protected]> wrote: > Hi Bob, > > Thanks, are there any specs as to what a 'normal' range for output would > be? I know working on my KWS-1 recently the mixers took a range from > 100mVrms up to 1-2Vrms . > > Jerry > > -----Original Message----- > From: Bob Camp <[email protected]> > Sent: Wednesday, November 6, 2024 5:18 PM > To: [email protected] > Cc: Larry Haney <[email protected]>; [email protected] > Subject: Re: [R-390] R-390 (non-A) - Low RF Gain or bad Antenna relay? > > Hi > > The issue isn’t so much a *dead* oscillator as one that is putting out > less signal than it should. To get proper mixing, you need a pretty strong > signal out of the oscillator. > > Bob > > > On Nov 6, 2024, at 4:56 PM, <[email protected]> <[email protected]> wrote: > > > > Hi Larry, > > > > > > > > Would I be able to hear strong stations across the bands if one of the > oscillators were not working? > > > > > > > > Jerry > > > > > > > > From: Larry Haney <[email protected]> > > Sent: Wednesday, November 6, 2024 3:26 PM > > To: [email protected] > > Cc: [email protected] > > Subject: Re: [R-390] R-390 (non-A) - Low RF Gain or bad Antenna relay? > > > > > > > > Jerry, Since you will be using a tube extender, you can check the > oscillators by scoping the mixer cathodes on the extenders. You may need > to decouple your scope using a 1 M res. > > > > > > > > Regards, Larry > > > > > > > > On Wed, Nov 6, 2024 at 12:11 PM Larry Haney <[email protected] > <mailto:[email protected]> > wrote: > > > > Jerry, Yes, you can do it with a tube extender. Use a small coupling > capacitor between sig gen and grid of the mixer. If a mixer oscillator is > not functioning, you can simulate it with your sig gen and feed it into the > cathode. It will require a little larger cap for this, maybe around 500 > pf. Have fun. > > > > > > > > Regards, Larry > > > > > > > > On Wed, Nov 6, 2024 at 12:00 PM <[email protected] <mailto:[email protected]> > > wrote: > > > > Hi Larry, > > > > > > > > Thanks. Do I need a set of extension cables to inject into the 3rd > mixer or would a tube extender work? I recently repaired my KWS-1 and > thought that was tight, but I didn’t have to disassemble module to test > each stage !! > > > > > > > > Any practical advice would be appreciated. > > > > > > > > Jerry > > > > > > > > From: Larry Haney <[email protected] <mailto:[email protected]> > > > > > Sent: Wednesday, November 6, 2024 2:00 PM > > To: [email protected] <mailto:[email protected]> > > Cc: [email protected] <mailto:[email protected]> > > Subject: Re: [R-390] R-390 (non-A) - Low RF Gain or bad Antenna relay? > > > > > > > > Hi Jerry, For setting the IF gain, you can try a couple things, > remember where the gain pot is at right now and then turn it all the way up > and see if that improves your problem. If not, put it back where it was at > (it's not critical). Are all the bands about the same deafness? > > > > > > > > The input to the 390 & As IF decks is high impedance (about 1 k ohm I > think), so the 390A suggests a 50 ohm shunt for use with the 25D sig gen. > If you can adjust your sig gen for 1 k ohm, that should work close enough > for you to tell if the IF deck is the problem or not. > > > > > > > > It sounds like it's the RF deck. You could work backwards from the > > 3rd mixer injecting a signal and see if the required signal input > > keeps getting considerably less and less the closer to the antenna you > > get. I'd check the 3rd var IF alignment real closely, you can > > manually lift the inductor bar up and see if the signal strength goes > > down right away or not. It should. One of the small SM coupling caps > > may have gone bad > > > > > > > > Regards, Larry > > > > > > > > On Wed, Nov 6, 2024 at 10:18 AM <[email protected] <mailto:[email protected]> > > wrote: > > > > I have checked all tubes and found two weak 6JB6 in the AF module which > I replaced. The primary issue seems to be inadequate RF gain. > > > > > > > > I did a side-by-side comparison of strong and weak stations above and > below 8MHz with my HF-380 and R-390. I found the R-390 was deaf to signals > with less than an S-6 reading on the HF-380. I also compared signal > strength to a Flexradio 6700 and the Flex and HF-380 gave similar > readings. > > > > > > > > Would adjusting the overall Gain (TM-11-856, para. 71 a and b) be a > reasonable next step? If my R-390’s Gain is indeed low, the adjustment > requires a signal generator with a Network, Impedance Matching device > (CU-406/URM-25F, part of the AN/ URM-25”. I have a Rigol signal generator > where the load impedance can be set to provide correct voltage readout. > Is there any recommended method when not using the AN/URM-25 and impedance > matching device? > > > > > > > > Jerry > > > > > > > > > > > > From: [email protected] <mailto:[email protected]> <[email protected] > > <mailto:[email protected]> > > > Sent: Monday, November 4, 2024 8:14 PM > > To: '[email protected] <mailto:[email protected]> ' > > <[email protected] <mailto:[email protected]> > > > Subject: R-390 (non-A) - Low RF Gain or bad Antenna relay? > > > > > > > > Several years ago, Don W5OR (SK) asked me to share administrator > > responsibilities with him to manage the r-390 mail list server. While > > I have several R-390/R-390A, I never had the need to repair any. So, > > this is my first post for help… > > > > > > > > My R-390 has gone partially deaf. It sits in a fan-ventilated rack > which rarely gets rolled around. Its last maintenance was in 2002 when Don > Heywood did an incredibly thorough job. It worked great until a few weeks > ago when it became completely deaf. My initial inspection found something > bizarre, the RF cable had popped loose (see attached picture) After > reconnecting, it was only partially deaf. I could tune in moderate and > strong signals across all bands but I need to set Local Gain to 7 or higher > just about where hum comes into the speakers. The best description is what > you might expect to hear if RF Gain is not at maximum. Also, another ‘clue’ > is I noticed that switching to CAL does not remove or attenuate a CW or > phone signal.. sounds same as if in AGC. I checked that the antenna relay > is working: > > > > > > > > * On powering to STBY – the relay clicks and pulls in visually and > checking both twin-ax connector pins, I confirmed both 2 pins are > grounded. > > * On switching to AGC or MGC – the relay clicks off and neither of > the twin-ax pins are grounded. > > * On switching to CAL – the relay clicks on again and the twinax > pins are grounded. The manual says in CAL, unlike in STBY, +180 volts de is > applied to the rf. if., af, and calibration oscillator stages and in both > STDBY and CAL, terminal 2 of CR801 is grounded to apply 6 volts dc to relay > K101. > > > > > > > > I also checked Break-In and that works in AGC giving complete silence, > but the manual says that’s achieved by grounding the AF output in addition > to grounding the antenna inputs. How does that prevent overloading the RF > section with a local transmitter? > > > > > > > > My 1st question is, why is there no signal attenuation when switching to > CAL? Is there anything in the electromechanics that could explain this? > Is this coincidental to the R-390 partial deafness or part of the same > problem? > > > > > > > > Pending some replies, my next step is to check the tubes in the RF and > audio stages but I’m hoping that my description may sound familiar to the > many experienced members of the list. > > > > > > > > TIA Jerry > > > > ______________________________________________________________ > > R-390 mailing list > > Home: http://mailman.qth.net/mailman/listinfo/r-390 > > Help: http://mailman.qth.net/mmfaq.htm > > Post: mailto:[email protected] <mailto:[email protected]> > > > > 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:[email protected] > > > > 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:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
