Okay, Larry. I thought that might be the case. I was able to make the endpoint adjustment and it's tracking extremely close now - at least end-to-end and I think points in between are quite good too. I need to do some more checking on everything now that the PTO is reinstalled.
Thanks! Barry - N4BUQ On Thu, Sep 19, 2024 at 12:20 AM Larry Haney <[email protected]> wrote: > OK Barry, That is certainly the right approach to take. I thought you > were already planning on what to do if the screw driver adjustment was not > enough. I hope it is. > > Regards, Larry > > On Wed, Sep 18, 2024 at 11:51 AM Barry <[email protected]> wrote: > > > Hi Larry, > > > > I'm sorry but I'm still a little confused. My intent of adjusting L701 > > would be by using a screwdriver on the endpoint adjusting core. If that > > doesn't give me enough range, then I presume I'd need to start modifying > > the C or L values but would start with just the core adjustment. > > > > Thanks again, > > Barry - N4BUQ > > > > Hi Barry, I believe that the total range of adjustment of L701 is about > > 7.5 kc (5 turns of wire). If you needed to only adjust it 1-2.5 kc to > get > > it back into range, I'd probably go the route of removing 1-2 turns, but > at > > about 1.5 kc per turn, you'd need to remove 3 turns and that makes the > > adjusting range quite small after that. It's doable, but a little > > restrictive. > > Regards, Larry > > > > On Wed, Sep 18, 2024 at 10:52 AM Barry <[email protected]> wrote: > > > >> Hi Larry, > >> > >> I'm curious why changing out a cap would be the first line of effort. > Is > >> that because there may not be enough change available from L701 to > correct > >> for 4 kc? > >> > >> Thanks, > >> Barry - N4BUQ > >> > >> > Hi Jim, Yes, I've done that and it works quite well. > >> > > >> > Barry, Since the EP is about 4kc off, I'd suggest using the capacitor > >> > adjustment method because removing 1 turn off of the L701 is not going > >> to > >> > be enough. Removing 2 turns really limits its adjustment range. Be > >> very > >> > careful with those 10 pf caps inside the pto, they are very fragile. > >> You > >> > should be able to calculate fairly close as to the value to put in > >> series > >> > with a 10 pf, and give it a little wiggle room for adjustment. > >> > > >> > Regards, Larry > >> > > >> > On Wed, Sep 18, 2024 at 9:07 AM Jim Whartenby via R-390 < > >> > [email protected]> wrote: > >> > > >> >> Since the trend is a reduced frequency range, something has obviously > >> >> increased in value internal to the PTO. There are two inductors and > >> three > >> >> capacitors in the circuit. The inductors have two ferrite cores so > >> there > >> >> are seven components in total that determine frequency. I have the > >> feeling > >> >> that the ferrite permeability has increased over time perhaps due to > >> >> shrinkage. I don't see how either coil can have increased in > >> inductance > >> >> without causing binding with their respective ferrite cores. Of > >> course it > >> >> is still possible that any or all of of the tank capacitors could > have > >> >> increased in value. > >> >> > >> >> I assume that the two 10 pF capacitors have either a positive or > >> negative > >> >> temperature coefficient of different slopes to compensate for the > >> operating > >> >> temperature of the PTO. Lifting one of the two 10pF caps and > placing, > >> for > >> >> example, a 100 pF NPO in series with it will subtract 1 pF from the > >> total > >> >> tank capacitance and raise the operating frequency without > >> significantly > >> >> changing the temco. This should preserve the end point coil > inductance > >> >> range. Has anyone tried this instead of removing a turn on the > >> endpoint > >> >> coil? > >> >> > >> >> Jim > >> >> > >> >> Logic: Method used to arrive at the wrong conclusion, with > confidence. > >> >> Murphy > >> >> > >> >> On Wednesday, September 18, 2024 at 10:04:39 AM CDT, Barry < > >> >> [email protected]> wrote: > >> >> > >> >> Sorry. The first line of that last paragraph had kc where it should > >> have > >> >> been MC (or Mc or MHz or...): > >> >> > >> >> I don't how the counter now shows 499.7 for the VFO set at 2.9550 MC > >> and, > >> >> conversely, the VFO frequency at 500.0 is now at 2.9548 MC. > >> >> > >> >> Thanks, > >> >> Barry - N4BUQ > >> >> > >> >> > Previously, I mentioned I have the endpoint data. > >> >> > > >> >> > VR Counter VFO Frequency (in MC) > >> >> > ---------- --------------------- > >> >> > +001.4 2.4550 > >> >> > 499.7 2.9550 > >> >> > -997.4 3.4550 > >> >> > > >> >> > That makes the counter span for 1000 kc of the VFO to be 1000 + > 1.4 + > >> >> 2.6 = 1004 > >> >> > kc. > >> >> > > >> >> > Switching to zeroing the VR counter at both ends: > >> >> > > >> >> > VR Counter VFO Frequency (in MC) > >> >> > ---------- --------------------- > >> >> > +000.0 2.4566 > >> >> > 500.0 2.9548 > >> >> > 000.0 3.4524 > >> >> > > >> >> > That makes the VFO span for 1000 kc on the counter to be 3452.4 kc > - > >> >> 2456.6 kc = > >> >> > 995.8 kc so 4.2 kc short. Hopefully the endpoint adjustment still > >> has > >> >> that > >> >> > much left in it and I won't need to open the can and perform any > >> surgery. > >> >> > > >> >> > I don't how the counter now shows 499.7 for the VFO set at 2.9550 > >> and, > >> >> > conversely, the VFO frequency at 500.0 is now at 2.9548 kc. > >> Something > >> >> must've > >> >> > moved just a tiny bit since I set it. > >> >> > > >> >> > Thanks, > >> >> > Barry - N4BUQ > >> >> > > >> >> >> Hi > >> >> >> > >> >> >> Using a impossible extreme case to keep the math easy: > >> >> >> > >> >> >> If your PTO covers (say) 900KHz rather than 1000 KHz, there will > be > >> a > >> >> 100KHz > >> >> >> “gap” that you can not tune to. > >> >> >> > >> >> >> Any significantly “too small” range would have the same impact. > >> (Yes, > >> >> there is a > >> >> >> bit of extra travel at the ends of the range so this does not get > >> >> totally > >> >> >> insane ….). > >> >> >> > >> >> >> Bob > >> >> >> > >> >> >>> On Sep 18, 2024, at 9:54 AM, Barry <[email protected]> wrote: > >> >> >>> > >> >> >>> Would a significant difference in span between bands be due to > the > >> >> first crystal > >> >> >>> oscillator? Otherwise, I'm not sure how that would occur. > >> >> >>> > >> >> >>> Thanks, > >> >> >>> Barry - N4BUQ > >> >> >>> > >> >> >>>> Hi > >> >> >>>> > >> >> >>>> As long as the end points still line up so you have a 1000 KHz > >> span > >> >> with one > >> >> >>>> being at 2955, the radio should be in reasonable shape. Having a > >> >> “gap” between > >> >> >>>> bands ( = a < 1000 KHz span) would be a PIA …. Fortunately that > >> >> rarely is the > >> >> >>>> case. > >> >> >>>> > >> >> >>>> There are still piles of R-390A’s sitting here or there …. > >> >> >>>> > >> >> >>>> Bob > >> >> >>>> > >> >> >>>>> On Sep 18, 2024, at 9:39 AM, Barry <[email protected]> wrote: > >> >> >>>>> > >> >> >>>>> I set the PTO's frequency per the manual (i.e. set the VR > >> counter to > >> >> any 500.0 > >> >> >>>>> reading and adjust the PTO to 2955 kc. The endpoint on the low > >> side > >> >> is > >> >> >>>>> different from the endpoint on the high side so I'm presuming I > >> have > >> >> just a bit > >> >> >>>>> of non-linearity; however, I think if I get the endpoints set > to > >> an > >> >> even 1000 > >> >> >>>>> kc, then any non-linearity will hopefully be minimal. I'm not > >> all > >> >> that > >> >> >>>>> concerned if the minor divisions aren't exact and will live > with > >> it > >> >> as long > >> >> >>>>> it's not too much. The trouble to tweak that may be much more > >> >> effort than it's > >> >> >>>>> worth to me. > >> >> >>>>> > >> >> >>>>> I wish I could've seen some of those "mountains"! I've seen > >> >> pictures of the > >> >> >>>>> stacks of blue-striper R-390A/URRs that sat out in the rain. > >> Sad. > >> >> >>>>> > >> >> >>>>> Thanks, > >> >> >>>>> Barry > >> >> >>>>> > >> >> >>>>>> Hi > >> >> >>>>>> > >> >> >>>>>> The gotcah is that the internal adjust coil may not have > enough > >> >> range to get the > >> >> >>>>>> PTO back to where it needs to be. You may need to get a bit > >> >> creative. Better to > >> >> >>>>>> do this *before* any of the other work. > >> >> >>>>>> > >> >> >>>>>> This is not a new issue. Back in the day, the military spent a > >> lot > >> >> of time and > >> >> >>>>>> money swapping out PTO’s. It was cheaper / easier to do that > >> than > >> >> doing a full > >> >> >>>>>> rebuild. There are stories of “small mountains” of PTO’s > >> building > >> >> up behind > >> >> >>>>>> repair depots as a result. Like any story, the size of those > >> >> mountains likely > >> >> >>>>>> got bigger and bigger with each telling of the story :) :) :). > >> >> >>>>>> > >> >> >>>>>> Bob > >> >> >>>>>> > >> >> >>>>>>> On Sep 18, 2024, at 8:28 AM, Barry <[email protected]> > wrote: > >> >> >>>>>>> > >> >> >>>>>>> Hi Bob, > >> >> >>>>>>> > >> >> >>>>>>> I see where the PTOs for the R-390/URR and R-390A/URR both > have > >> >> end point > >> >> >>>>>>> adjustments. L701 performs that in both. The schematic I > see > >> for > >> >> the > >> >> >>>>>>> R-390A/URR conveniently labels that as such on the schematic. > >> RM > >> >> >>>>>>> 11-5820-357-35 calls it out on page 12, Paragraph 12-b > defines > >> the > >> >> function of > >> >> >>>>>>> that coil. I just wasn't seeing that last night. I sure > wish > >> I > >> >> had a > >> >> >>>>>>> searchable PDF for the R-390/URR's service manual. > >> >> >>>>>>> > >> >> >>>>>>> Thanks, > >> >> >>>>>>> Barry - N4BUQ > >> >> >>>>>>> > >> >> >>>>>>>> Hi > >> >> >>>>>>>> > >> >> >>>>>>>> Motorola most certainly made their own PTO’s for the radios > >> they > >> >> supplied. Long > >> >> >>>>>>>> ago I talked to the folks who did the linearity adjustments > on > >> >> them. They still > >> >> >>>>>>>> had (not so) fond memories of doing those adjustments. > >> >> >>>>>>>> > >> >> >>>>>>>> Bob > >> >> >>>>>>>> > >> >> >>>>>>>>> On Sep 17, 2024, at 11:29 PM, Barry <[email protected]> > >> wrote: > >> >> >>>>>>>>> > >> >> >>>>>>>>> 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 > >> >> ______________________________________________________________ > >> >> 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
