Hi Larry, Thank you so much for pointing to that document. I now see the endpoint coil, the corrector stack, etc., in very clear photos. Hopefully just a simple endpoint adjustment will get me close enough but won't know until I get that adjusted.
Thanks again, Barry - N4BUQ On Wed, Sep 18, 2024 at 9:14 AM Larry Haney <[email protected]> wrote: > Hi Barry, Since the 390 PTO is mechanically the same as the 390A PTO made > by Collins (has the corrector stack on the inside), the document I wrote on > the Collins 390A PTO should be applicable to the 390 PTO. Here's a link to > it in the tutorials section: R390A My Collins PTO Observations > <https://www.r-390a.net/R390A_My_Collins_PTO_Observations.pdf>. I think > Collins was the only manufacturer of the 390 PTO. FYI - removing a turn > off of the EP adjustment coil, L701 reduces the EP adjustment range. This > can be a problem in the future when readjustment is necessary. > > Changing the ratio of L to C can put a linearity bubble in the middle of > the range. Small changes should not be an issue. Also, removing the > covers off of the PTO changes the operating frequency quite a bit, but is > restored when replaced. And, adjusting the 'stack' is quite challenging. > Unless something specific has happened to it, its current state should be > OK. > > Working on the internals of these can be frustrating and time consuming - > be prepared. > > Regards, Larry > > On Wed, Sep 18, 2024 at 4:58 AM Barry <[email protected]> wrote: > > > 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 ______________________________________________________________ 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
