[TMC] VOX-3 question

Wed Apr 13 11:53:11 EDT 2022

I dove a bit into the "S Documents" doing a word search on VOX. There are
22 related documents! Many of them are very interesting and applicable. I'm
just starting to dig in, but have found a document on mechanical setup of
the capacitors in the master oscillator and how to align the control
shafts, a calibration procedure for the VOX-5, an interesting doc on
applicable crystals, the one Nick provided the link to and many others.
This "S" file is a gold mine!

One thing to look out for is that the titles of the documents
sometimes seem completely unrelated to the actual content. It's weird to
me, but they must have had reasons for naming some of them the way they
did. The important takeaway for me is to do the word search and look at
everything! There are gems hidden in documents whose titles seem completely
unrelated to what I am looking for.

Thanks again for pointing this file out. It is awesome!

Chris

On Tue, Apr 12, 2022 at 2:33 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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