Hi Jerry, OFF: 520k CW: 583k CCW: 638k
Those don't exactly meet the specs. I probably have more than one drifted resistor that I need to address at some point. So strange that so many of those readings are so far off in your radio. It's almost as if another connector is loose or making poor connections. I presume you've reseated P117? Hope that helps, Barry - N4BUQ > 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
