I can get greater than -7v without a 50-ohm terminator but not with it. From what I can measure with an HP-410C, the HP-8640B needs the terminator to accurately reflect the voltage on its meter and, therefore, I should be using the terminator for this.
Of course, I could most likely get that output with, perhaps, 225uv and I may try that just to see how I like it. I need to do some voltage and resistance checks in the IF deck. I haven't done that yet and I suspect there are some drifted resistors. If not that, then I could have some weak tubes. I'll know more once I run some checks. Thanks, Barry - N4BUQ Thanks, Barry - N4BUQ On Fri, Oct 11, 2024 at 10:52 PM Larry Haney <[email protected]> wrote: > > Hi Barry, If your 390 is in correct working order then Chuck's short cut is > good to use. But if you are not positive that it is working correctly, then > use the '55 tech ref method you ref'd. And, the IF input is not low > impedance, so the sig gen output will need to have a 50 ohm load on it and > the gain adjust must not be at the ends of its adjustment. > > Regards, Larry > > On Fri, Oct 11, 2024 at 7:49 PM Barry Scott <[email protected]> wrote: >> >> Yes, that's the 1955 version that I was referring to where it >> describes using the IF input and a 30% modulated 455kc signal at 150uV >> to produce -7.0V at the Diode Load. The later paper manual I have >> from 1962 uses the antenna input for this. Chuck Rippel's method uses >> strictly the noise level and the LINE GAIN meter to set it. I'm a bit >> confused as to what's the best way. >> >> Thanks, >> Barry - N4BUQ >> >> On Fri, Oct 11, 2024 at 8:56 PM Jim Whartenby via R-390 >> <[email protected]> wrote: >> > >> > https://bama.edebris.com/download/military/r390/Collins_R390_1953.pdf >> > >> > Logic: Method used to arrive at the wrong conclusion, with confidence. >> > Murphy >> > >> > On Friday, October 11, 2024 at 06:16:31 PM CDT, Barry Scott >> > <[email protected]> wrote: >> > >> > Looking at the older (1955) vs newer (1962) manuals for the R-390/URR, >> > the older one describes setting the GAIN ADJ pot using input directly >> > into the IF deck; whereas the newer one describes setting it using the >> > antenna input jack. Is one method any better or preferred to the >> > other? >> > >> > One of the reasons I'm asking is that when I try the direct input to >> > the IF deck method, I can't get -0,7V on the Diode Load which makes me >> > think I have a gain problem in the IF deck. >> > >> > I know there were several posts about this over the years but I've >> > lost track of those for the most part so I thought I'd ask. >> > >> > Thanks, >> > Barry - N4BUQ >> > ______________________________________________________________ >> > 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
