[Boatanchors] More on the VF-1 and parallel VR tubes

[1oldlens1]

I wonder which edition this is.  I have RC-24. Which does not even list gas regulator tubes.    There are electronic regulated supplies described in several text books. These use a gas tube as the reference.  The most exact reference tube is the 5651.  This cannot handle much current but is intended to be a precise and stable reference.    The most common arrangement for a gas tube is to use a dropping resistor such that the tube draws its maximum current with no load. However,  one can reduce the resistor value so that the regulator will be in the center of its range with more current through the resistor. This carries the risk of damaging the tube if the load is lost. Sent from my Galaxy
-------- Original message --------From: JAMES D COMSTOCK <comnoz2 at comcast.net> Date: 5/5/22  10:23 PM  (GMT-08:00) To: k4to at arrl.net, Dave Sublette <k4to.dave at gmail.com>, JAMES HANLON <knjhanlon at msn.com> Cc: boatanchors at mailman.qth.net Subject: Re: [Boatanchors] More on the VF-1 and parallel VR tubes According to the RCA tube book two tubes can be run in parallel with a 100 ohm resistor in series with each tube. [new one to me]I don't imagine that would make a very good regulator. A 6L6 or similar used along with an 0A2 would be a better way. [but more complicated] Jim> On 05/05/2022 6:01 PM Dave Sublette <k4to.dave at gmail.com> wrote:> >  > Good evening,  I have left the VF-1 running for the past 5 to 6 hours with> a very stable and accurate frequency counter connected.  I can tell you> that the frequency has varied less that +/- 200 Hz in that time.  However> the case is off.  I will repeat this after I get the case installed> sometime in the future.> > I find it interesting to note that this is the same VF-1 I asked for advice> about a few weeks ago.  At that time I asked if it would be better to> convert the VF-1 to solid state(which would eliminate the heat/drift> problem) or try to keep it original.  The advice was unanimous to keep it> original.> > However, now I find several suggestions that I remove the OA2 circuit in> order to minimize drift.  I only have two questions.  What drift?  I> haven't seen any (but expect to when I get it into the case).  But, what> happened to the overwhelming sentiment for keeping the unit in original> configuration?  I can't have it both ways.> > Now I don't really expect an answer.  I just find it interesting to think> about what has transpired.> > I really do enjoy this group and have learned a lot.  I am not a> "Boatanchor" guy per se.  But I was given this unit recently from the> estate of a dear friend who died in an auto accident a couple of months> ago.  It has only sentimental value for me as it was built by him and used> as one of his first rigs way back when. I also have his DX60, which I have> refurbished and have on the air.  I use the rig as part of the Novice Rig> group activities on Monday night.  It has been a rewarding experience.> > Thank you all again for your help.> > 73,> > Dave, K4TO> > On Thu, May 5, 2022 at 7:37 PM JAMES HANLON <knjhanlon at msn.com> wrote:> > > First about the VF-1 ... That 5K dropping resistor and for that matter the> > OA2 also will get pretty warm and may contribute to some drift in the VF-1> > if they are in theVF-1 cabinet.  You might be better off to put them in the> > power supply and just run a regulated 150 volt line to the vfo.  The Viking> > 122 vfo has its dropping resistor inside the vfo cabinet and it is more> > drifty than it needs to be because of that.> >> > As to VR's in parallel, I actually did do that successfully in two> > applications starting back around 1952.> >> > First off, my brother and I were running a BC457 Command Set as a vfo for> > our transmitter, and we needed a source of regulated 300 volts at something> > more than 40 ma for the oscillator plate and final screen voltages.  We> > used four OD3/VR-150s in series-parallel with balancing resistors to get> > around the current-hogging problem, and ran that power supply and rig until> > about 1960.> >> > Also, our final amp was a pair of push-pull 809s which require grid bias> > of 75 volts and ran 50 ma of grid current in CW, 62 ma in phone.  We got> > our grid bias supply by putting two 0A3/VR-75s in parallel (with balancing> > resistors) with an electrolytic filter capacitor connected across them to> > ground in series with the grid-return lead.  At the first application of> > grid drive (when we tuned up or just went on the air with existing> > adjustments), the grid current would flow through the VRs and ignite them> > and the capacitor would charge up to 75 volts.  Removing drive would> > extinguish the VRs but leave the capacitor charged to the 75 volts> > necessary to keep the final in cut-off with no drive.  So we got along> > without having to build a separate bias supply.  Again, that ran happily> > for a good eight years with no trouble.> >> > So it can be done.> >> > By the way, in 1960 my brother had graduated from college and I was about> > to do the same, so we divided up our station gear.  I took our HRO-50, and> > brother Bob took everything else.  I think I got the better end of the> > deal!  I'm still using the HRO with some additions further along the way> > like a product detector, SSB AVC, mechanical filters, and regulated> > filament voltage on the local oscillator, mixer, and bfo.  It is close to> > my best receiver and certainly still is my favorite.> >> > Jim, W8KGI> > ______________________________________________________________> > Boatanchors mailing list> > Home: http://mailman.qth.net/mailman/listinfo/boatanchors> > Help: http://mailman.qth.net/mmfaq.htm> > Post: mailto:Boatanchors at mailman.qth.net> >> > List Administrator: Gary Harmon, K5JWK> > ** For Assistance: gharmon at idworld.net **> >> >> > This list hosted by: http://www.qsl.net> > Please help support this email list: http://www.qsl.net/donate.html> > Message delivered to k4to.dave at gmail.com> >> ______________________________________________________________> Boatanchors mailing list> Home: http://mailman.qth.net/mailman/listinfo/boatanchors> Help: http://mailman.qth.net/mmfaq.htm> Post: mailto:Boatanchors at mailman.qth.net> > List Administrator: Gary Harmon, K5JWK> ** For Assistance: gharmon at idworld.net **> > > This list hosted by: http://www.qsl.net> Please help support this email list: http://www.qsl.net/donate.html> Message delivered to comnoz2 at comcast.net______________________________________________________________Boatanchors mailing listHome: http://mailman.qth.net/mailman/listinfo/boatanchorsHelp: http://mailman.qth.net/mmfaq.htmPost: mailto:Boatanchors at mailman.qth.netList Administrator: Gary Harmon, K5JWK** For Assistance: gharmon at idworld.net **This list hosted by: http://www.qsl.netPlease help support this email list: http://www.qsl.net/donate.htmlMessage delivered to 1oldlens1 at ix.netcom.com