That first line should have been: Regarding the tutorials, I'm wondering which, if any, might apply to the PTO in the R-390/URR.
Thanks, Barry - N4BUQ > Hi Larry, > > Regarding the tutorials, I'm wondering which might apply to the PTO in the > R-390A/URR. I see most(all?) of them are regarding the COSMOS units but am > wondering which PTO is in the R-390/URR and whether any of the > rebuild/linearity documents apply to that one. Were all the R-390/URR PTOs > made by Collins and no COSMOS in that version? > > Mine is running just a bit fat - maybe 1.5 kc end-to-end. I have the actual > numbers written down and can post that when I get back to the workbench. From > what I remember, removing a turn shortens the end-to-end but perhaps > additional > C would work as well. I don't know what effect that might have on linearity > but I don't think it should. > > The R-390A/URR PTO has an endpoint adjustment. Does this exist for the PTO in > an R-390/URR? > > Thanks, > Barry - N4BUQ > >> Hi Barry, I thought what you wrote makes sense and is correct. It's good >> that you are understanding how it all works. It makes diagnosys so much >> easier. Good going. >> >> If you're interested in more reading on the 390A PTO's, there are 3 docs on >> our website in the repair tutorials section by Tom Marcotte, Jim Miller and >> myself. >> >> Regards, Larry >> >> On Mon, Sep 16, 2024 at 5:51 AM Barry Scott <[email protected]> wrote: >> >>> Okay, Larry. Thanks for the reply. >>> >>> On further reading, the VFO is a Hartley design and, given that the >>> frequency formula for a Hartley is an inverse function of the LC values, >>> presuming that at xx 000, the iron core is "out" of the coil and a >>> clockwise turn of the KC knob causes the core to be pushed further inside >>> the coil increasing the L, then the frequency would indeed drop with CW >>> motion of the knob. Sorry for the awkward way of stating that but I think >>> it makes sense to me. >>> >>> Thanks again, >>> Barry - N4BUQ >>> Thanks, >>> Barry - N4BUQ >>> >>> >>> On Sun, Sep 15, 2024 at 11:10 PM Larry Haney <[email protected]> wrote: >>> >>> > Hi Barry, You are absolutely correct in your deductions. When the KC is >>> > at its lowest of 000, the vfo is at its highest (3.455 mh). >>> > >>> > Regards, Larry >>> > >>> > On Sun, Sep 15, 2024 at 7:23 PM Barry Scott <[email protected]> >>> > wrote: >>> > >>> >> Looking at the simplified schematic for the 3rd mixer (V205), the output >>> >> from the 2nd mixer (V204) tunes from 3 to 2 MC and the VFO tunes from >>> >> 3.455 >>> >> MC to 2.455 MC yielding a constant 455 kc mixer product. Is it correct >>> to >>> >> interpret those numbers to mean that if the counter starts at XX 000 >>> and >>> >> the KC control is rotated CW to XX +000 the VFO's output frequency >>> starts >>> >> at 3.455kc and falls 1000 kc for 10 turns CW on the KC knob? >>> >> >>> >> I'm asking because I want to know what the frequency of the VFO is >>> >> supposed >>> >> to be when the dial is at XX 000 and I presume it's 3.455 kc but >>> wanting >>> >> to make sure. >>> >> >>> >> 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 ______________________________________________________________ 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
