[TMC] VOX-3 question

Tue Apr 12 19:19:35 EDT 2022

Thanks JP, this comes pretty handy!

I was totally unaware of the existence of this document.

Should be helpful to you, Chris!

73, Meir WF2U
Landrum, SC
⁣

On Apr 12, 2022, 5:34 PM, at 5:34 PM, Nick England <navy.radio at gmail.com> wrote:
>Yep - I figured there was an S but I couldn't remember where they were
>squirreled away.
>See page & of S-110 for RF section alignment....
>https://tmchistory.org/tmc_drawings/drawings_db/s/s-docs_100_199/s_110.pdf
>
>Have fun, Chris.....
>Nick England K4NYW
>www.navy-radio.com
>
>
>On Tue, Apr 12, 2022 at 4:50 PM John Poulton <jp at cs.unc.edu> wrote:
>
>> 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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