Hi Gary, Pin 7 on V201 was changed to go directly to ground, so that is good that change is on your RF deck.
Regards, Larry On Sun, Nov 26, 2023 at 12:36 PM <[email protected]> wrote: > After pulling the RF module and tracing the wiring on V201, I am not sure > how this radio ever worked. Pin 7 has a wire that goes through the hollow > metal center of the tube socket and across the bottom tube and is hooked up > to pin 3 on the other side of the tube socket which is the ground side of > the filament on the tube. Of course it reads 0 ohms! Unfortunately, > everything is so tight in there, I am not sure I have the skills to > unsolder and re-solder. Before I move forward with trying, can anyone > confirm that the schematic is correct and that I won’t bugger everything up > if I rewire as per the schematic? > > > > Thanks. > > > > *From:* [email protected] <[email protected]> > *Sent:* Sunday, November 26, 2023 12:44 PM > *To:* 'Larry H' <[email protected]> > *Cc:* '[email protected]' <[email protected]> > *Subject:* RE: [R-390] R-390a not receiving below 8 MHz > > > > To continue the story, I used tube extenders and measured the voltages and > resistances of V201 to V206 (I couldn’t get both the tube extender and tube > on V207). The most interesting readings come from V201 as follows: > > > > Tube V201 > > Pin # > > V to Gnd > > Reading > > Ω to Gnd > > Reading > > 1 > > -0.4 > > -0.07 > > ∆1 M > > 729K > > 2 > > 2.8 > > 1.94 > > 220 > > 242 > > 3 > > 0 > > 0 > > 0 > > 0 > > 4 > > 6.3VAC > > 5.9VAC > > 0.1 > > 0.2 > > 5 > > 185 > > 185.3 > > 20K > > 23.7K > > 6 > > 154 > > 160 > > 24K > > 26.4K > > 7 > > 2.8 > > 0 > > 220 > > 0 > > > > From a review of the schematic, pins 2 and 7 are supposed to be connected > together so they should both have the same voltage and resistance. > However, you can see that it not the case. When I pulled the tube and > checked the resistance between pins 2 and 7, it was infinite so, whatever > connection the schematic says should be there, is not. So, time to pull > the RF module but I may have to wait until later to do that. > > > > Thanks for reading. > > > > 73 > > Gary > > > > *From:* [email protected] <[email protected]> > *Sent:* Sunday, November 26, 2023 9:09 AM > *To:* 'Larry H' <[email protected]> > *Cc:* '[email protected]' <[email protected]> > *Subject:* RE: [R-390] R-390a not receiving below 8 MHz > > > > Folks, > > > > The saga continues (but so does the fun!). I think I have narrowed the > problem down to either the VFO Oscillator or the RF module. I have put > known working IF, audio and Power Supply modules in the radio and no > difference. > > > > I did find out why I couldn’t get a calibrate signal below 6 MHz. > Apparently, Z213, the middle one, had some sort of obstruction in the coil > form that prevented the ferrite slug from going in more than about half > way. If I had some sort of boring tool that was exactly the right size, I > might be able to bore out the obstruction. Instead, I replaced the coil > with one from a parts RF chassis and now I get the calibrate signal below 6 > Mhz. But, still very low audio (and noise) – both almost non-existent. I > can receive WWV at 10 MHz and 15 MHz (I will try 5 MHz tonight, now that I > appear to have some reception below 6 Mhz) but I still cannot receive > strong BCB stations in the area. > > > > Time to figure out how to troubleshoot the RF module and the VFO Module. > > > > Stay tuned, if you’re interested. > > > > 73 > > Gary > > > > *From:* [email protected] <[email protected]> > *Sent:* Monday, November 20, 2023 6:44 PM > *To:* 'Larry H' <[email protected]> > *Subject:* RE: [R-390] R-390a not receiving below 8 MHz > > > > Larry, > > > > Thanks again for all your comments. I found a half hour to check out the > radio further today and tightened all of the screws on the IF module > including the ones on ground lugs and tube sockets. The readings are now: > > > > IF Subchassis > > J512 Pin > > Ω to Gnd > > Reading > > 1 > > Inf > > Inf > > 2 > > 50K > > 54.2K > > 3 > > 54K > > 55K > > 4 > > 500K > > 486K > > 5 > > Inf > > Inf > > 6 > > Inf > > Inf > > 7 > > Inf > > Inf > > 8 > > Inf > > Inf > > 9 > > Inf > > Inf > > 10 > > 440K > > 458K > > 11 > > Inf > > Inf > > 12 > > 27 > > 66 > > 13 > > Inf > > Inf > > 14 > > 0 to 20 > > 16 > > 15 > > 132K > > 135.4K > > 16 > > 100K > > 108.4K > > 17 > > 0 > > 0.4 > > 18 > > 0 > > 0 > > 19 > > Inf > > Inf > > 20 > > 0.5 > > 0.6 > > As you can see, the only out of tolerance reading is J512-12. On review > of the schematic, there is supposed to be a 27 ohm resistor to ground, > R548. When I looked at the colour bands on the resistor, it is actually a > 68 ohm resistor. I guess the question is – should I change this to a 27 > ohm resistor? > > > > More to come, I am sure. > > > > Regards, > > > > > > *From:* Larry H <[email protected]> > *Sent:* Monday, November 20, 2023 12:47 AM > *To:* [email protected] > *Subject:* Re: [R-390] R-390a not receiving below 8 MHz > > > > Hi Gary, I see that a lot of readings that should be 0 are not - this is > an indication that the grounding on these points is a problem. That is a > very important item to fix. Now for j208-E, that is the agc line in the rf > deck and should read as you have listed, 1.8 M Ohms, so that's ok. j208-F > is the filament line and may be ok. > > > > J512-6 is the open agc line in the IF deck and should read open - your > reading indicates this is a very bad problem and must be fixed. J512-12 is > in the c/l meter bridge - 69 ohms may be ok there. This higher value may > allow it to read higher and reach 100 db, where 27 may not. Leave it and > check the c/l with 100,000 uv in. > > > > J620-5 & 7 are indeed the 800 cps filter. You don't need it for the > basic function of the rx. > > > > Have fun. > > > > Regards, Larry > > > > On Sun, Nov 19, 2023 at 3:36 PM <[email protected]> wrote: > > Folks, > > > > Here are my findings with respect to the substantially “off” resistance > readings: > > > > AF Module – J620: 5 This goes to the 800cps bandpass filter and, since it > is infinity instead of the expected 200Ω, I will have to assume that the > filter is open and non-functional. When I try it with the current issues I > am having, rather than hearing an incredibly faint WWV, I hear nothing. > > > > IF Module: 6 – this is the AGC line and appears to go to ground in 3 > places – 1. Through R516 (22K) and C519 (5000pf); 2. Through R507 (22K) and > C512 (5000pf); 3. Through R501 (22K) and C502 (5000pf); Since this is > supposed to read infinity but reads 33.5KΩ, would it be an appropriate test > to check the 3 capacitors for leakage? > > > > RF Module: E - – this is the AGC line and appears to go to ground in 1 > place – Through R206 (22K) and C319 (5000pf); Since this is supposed to > read infinity but reads 1.795MΩ, would it be an appropriate test to check > the capacitor for leakage? > > > > Thanks in advance for your help. > > > > Regards, > > > > > > Please help support this email list: http://www.qsl.net/donate.html > > <snip> > > ______________________________________________________________ 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
