VPI JMW 12.7 Spindle/pivot distance

Thanks to all

Best regards,
Paulo

This is an old thread, but it caught my attention
because I have been trying to refine the alignment
geometry on my VPI 12.7 tonearm (mounted on a VPI Classic 3 TT). I recently overcame my reluctance
to buy a Feickert protractor, and since I already
own a Fozgometer it didn't make sense to cavil
over a few more dollars to do the job right. I
spent about an hour tinkering with the protractor,
and the spindle-to-pivot distance proved to be 297
mm. That's 1 mm shorter than the 298-299 mm range
stated by VPI, and roughly 5mm shorter than the
302 mm measurement mentioned in this thread. I
have no explanation for this anomaly, except
perhaps that VPI was a hair off mounting the
tonearm to the plinth. After I finished aligning
the cartridge, I used the Fozgometer to adjust the
azimuth, and eventually got the signal strength of
both channels to within 0.5 db of each other. Good
enough, said I.

Sdcampbell -

If it's like my JMW 10 - and it looks like it is in photos - there should be a set screw on the left side, just below the height adjust knob. You can adjust the arm to spindle distance by rotating the arm base. I used the JMW jig and snugged the base into the jigs "vee". Measuring the pivot to spindle distance by ruler with the arm removed showed it to be spot on - 250 in my case. It had been maybe one or two mm long. That was enough to create sibilance and mistracking problems that drove me nuts for a year. I attacked the problem from every parameter and learned a lot in that year. Setting the digital scale to the side of the platter and taking the reading at the same height as the record surface is critical. I wonder if that is a unipivot thing. The Fozgometer is a fantastic tool. It got me in the ballpark but the best azimuth setting was found only by slight tweaking after the initially setting for balanced output. The difference was big in my case. YMMV

I Didn't read all the responses, but it is 299.5 mm.

Wlutke:
Thanks very much for your helpful post. I was not aware of the set screw, so I'll try adjusting the spindle to pivot distance. I'll make a follow-up post later this week.
Best regards,
Scott C-