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

[Dave Sublette]

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
>