The only thing I can see that might cause any of that would be if R543 were shorted which doesn't seem very likely.
Thanks, Barry - N4BUQ On Thu, Nov 7, 2024 at 1:29 PM <[email protected]> wrote: > > Before I replace R544, I wonder what caused it to fail. Checking voltages > per manual, with Limiter at maximum 10, there should be 0 vdc at the plate > (pin 6) or grid (7) or cathode (8) which I confirmed. However, with Limiter > switched off there should only be 40vdc at the plate, grid and cathode and I > find +155vdc. Does this make any sense? > > Jerry > > > > -----Original Message----- > From: [email protected] <[email protected]> On Behalf > Of [email protected] > Sent: Thursday, November 7, 2024 2:08 PM > To: [email protected] > Subject: Re: [R-390] R-390 (non-A) - Low RF Gain or bad Antenna relay? > > I unplugged P117 from J517. All connections from P117-9 and P119-10 to > Limiter switch are intact. There is no continuity from V507B-8 (cathode) to > J517-9. I checked directly at the tube sockets; V507B cathode and V510 > cathode are continuous as per schematic so that rules out issues at the tube > sockets. It looks like it can only be R544... so now to remove the IF module. > > More to follow............ > > Jerry > > -----Original Message----- > From: Jacques Fortin <[email protected]> > Sent: Thursday, November 7, 2024 12:10 PM > To: [email protected]; 'Barry Scott' <[email protected]> > Cc: [email protected] > Subject: RE: [R-390] R-390 (non-A) - Low RF Gain or bad Antenna relay? > > Jerry, looks like R544 is open, or just not there anymore ! > > 73, Jacques, VE2JFE in Montreal > > -----Message d'origine----- > De : [email protected] <[email protected]> De la part > de [email protected] Envoyé : 7 novembre 2024 10:46 À : 'Barry Scott' > <[email protected]> Cc : [email protected] Objet : Re: [R-390] R-390 > (non-A) - Low RF Gain or bad Antenna relay? > > Hi Barry, > > Could you do me a favor and also check resistance on V507B (Neg Peak Limiter) > pin 8 cathode -- It should read 500k (Limiter knob at full CW) and 450k with > Limiter switch OFF - I read an open circuit or resistance > 10Meg. The > cathode of V507B is tied to the cathode of V510 (pin 3) which also reads > open on my DMM. > > Thanks in advance > Jerry > > -----Original Message----- > From: Barry Scott <[email protected]> > Sent: Wednesday, November 6, 2024 10:52 PM > To: [email protected] > Cc: [email protected] > Subject: Re: [R-390] R-390 (non-A) - Low RF Gain or bad Antenna relay? > > I just checked resistance from V506 Pin 7 to ground in my R-390/URR and it > checks a few ohms over 820 ohms. > > Thanks, > Barry - N4BUQ > > On Wed, Nov 6, 2024 at 8:38 PM Barry Scott <[email protected]> wrote: > > > > That resistance measurement seems quite odd. R536 is supposed to be > > 820 ohms. Unless C523 is bad, I don't see how there should be > > anything much less than 820 ohms at pin 7 of V506 yet the resistance > > diagram shows 700 ohms. 99 ohms seems very wrong. > > > > Thanks, > > Barry - N4BUQ > > > > On Wed, Nov 6, 2024 at 8:12 PM <[email protected]> wrote: > > > > > > Update.... > > > > > > I checked voltages and resistances per TM 11-5820-357-35 (09 March 1962) > > > for the IF amps V501 - V506. I don’t know if my R-390 had any mods, its > > > SN 1256, but all the results were very close to the listed values except > > > for V506, 6th IF amp. The cathode should read 700 ohms to ground and > > > 8.2vdc and I find 99 ohms and 2.3vdc. The schematic shows the cathode > > > bias resistor of 800 ohms and a 15ohm pot for carrier meter adjustment. > > > There is a decoupling cap 0.1uF off the cathode that if leaky could bring > > > the resistance down to my reading. But would this be enough to drop my > > > gain so dramatically? > > > > > > 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] > > > > > > 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 > > ______________________________________________________________ > 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 ______________________________________________________________ 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
