[TMC] VOX-3 question

[John Poulton]

I haven't had time to research this, but it's possible that one of the
S-documents (Specifications, located under "S" in the Drawings part of
tmchistory.org) may include a document that outlines the factory procedure
for VOX alignment.  They exist for some TMC products, but not all...

And, I'm assuming you guys already checked the various manuals for the VOX..

Sorry not to be more help!  This week has turned into a bit of a nightmare,
time-wise.

73, John K4OZY



On Tue, Apr 12, 2022 at 11:38 AM Chris Bolkan <bolkyboats at gmail.com> wrote:

> Hi Meir!
> Thank you for that restoration link. I completely missed that. There is
> so much on John's site! I will check it out.
> It is unfortunate that the frequency multipliers have no calibration
> procedure. I'm not as troubled about fiddling with the multipliers as I am
> by further messing up the tracking and endpoints of the master oscillator.
> Best regards,
> Chris
>
> On Tue, Apr 12, 2022 at 4:19 AM Meir Ben-Dror WF2U <wf2u at ws19ops.com>
> wrote:
>
> > Chris,
> >
> > The only procedure for disassembling and repairing/calibrating the MO is
> > in the link
> >
> >
> https://www.tmchistory.org/tmc_restoration/paul_spivak_docs/gpt_750_mo_repair.htm
> > .
> > The GPT-750 MO is identical to that of the VOX and PMO series master
> > oscillators.
> > In the procedure covered there is no mention of how to align the
> > multiplier/output stages.
> >
> > Good luck with the VOX-3.
> >
> > 73, Meir WF2U
> > Landrum, SC
> >
> > On Apr 11, 2022, at 7:27 PM, Chris Bolkan <bolkyboats at gmail.com> wrote:
> >>
> >> Hi TMC lovers!
> >>
> >> I now have the VOX-3 back together and working. Everything seems to
> >> function more or less. The master oscillator works very well putting
> out a
> >> nice sinewave throughout its frequency range.
> >>
> >> Unfortunately, I lost track of the exact relationship of the tuning
> shaft
> >> to the counter dial, and of exactly where within the almost inch travel
> of
> >> the calibration slug, the movement limits are established by the control
> >> mechanism for it.
> >>
> >> So, even though I set the counter dial to be correct at 3Mhz, it is off
> a
> >> bit at each end and I am not sure if placing the calibration slug in
> >> another segment of its travel will help.
> >>
> >> I did not mess with the fancy eccentric calibration tracking mechanism
> >> built into the master oscillator capacitor. All I did there was
> carefully
> >> clean and lube everything so it all worked again. I think if there was a
> >> way to calibrate the end points, it might be pretty close in the middle,
> >> but I am not sure.
> >>
> >> The other thing that doesn't seem exactly right are the frequency
> >> multipliers. They all work...sort of.....with reduced amplitude and a
> funky
> >> relationship to the output control, where the output control "peaks" the
> >> output rather than just acting like a level control. The output
> waveforms
> >> are not super clean either with differing amplitudes over many cycles
> >> probably indicating they need to be tuned up.
> >>
> >> I am only starting to dive into this, but thought I would ask if anyone
> is
> >> aware of a factory calibration or setup procedure for the VOX when it
> was
> >> originally being built. I think if one exists it would be very useful to
> >> me. The VOX-5 manual I have is very helpful but does not dive into the
> >> areas I took this thing apart so does not provide what I am looking for
> >> unless I have somehow overlooked it.
> >>
> >> Thanks in advance if you can point me in the right direction!
> >>
> >> Best regards,
> >>
> >> Chris Bolkan
> >> KI7NXY
> >> ------------------------------
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