[TMC] VOX-3 question

[Meir Ben-Dror WF2U]

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, 7:27 PM, 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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