Which protractor to use ? (DUAL CS-750)

Today I bought a nice Dual CS-750 turntable in almost mint condition for 25€. The store owner had no idea how to value the thing...

Anyway, wich protractor should I use ? I'm not that experienced with that stuff. I used
"Rega Baerwald alignment protractor v.2"
from Vinylengine. For the sole reason that it was the closest to the 221mm arm lenght. I have no idea how to use their generator program.

 

You can go back to vinylengine and check the specs for arm effective length and overhang, they are below ...

Description
Features microprocessor control and aluminium tubular tonearm

Specifications
Drive: microprocessor controlled quartz belt drive

Speeds: 33, 45 and 78rpm

Wow and flutter: 0.023% WRMS

Rumble: 80dB

Platter: 302mm non magnetic

Effective length: 221mm

Overhang: 18mm

Then go to the Conrad Hoffman site ... Conrad's Free Stuff ... and download the arc protractor generator. Run it and plug in the spindle to pivot distance, which should be the effective length from above minus the overhang, or 203mm (you could measure to be sure, if you have the tools), and select the alignment you want and what groove radius you want to optimize for (DIN/IEC/Typical). Then print and verify scaling.

And you should then wind up with something like below, this is my table, but you get the idea, just adjust the overhang and platter/protractor position until the stylus tip follows the arc, and then without moving the platter or protractor anymore, set offset at one of the grids, and double check at the other grid, and then check arc again before final tightening of screws...

 

Guess I was actually doing the right thing then. Worked like a charm. (didn't have to alter anything at all)

 

OK, guess I'm missing something (happens all the time) but I'm not totally clear what you mean. The protractor you initially used was for Rega, which has about 222mm pivot to spindle distance, but the Dual apparently has 203mm pivot to spindle based on the VE info above.

 

dscn3169.jpg | picload.org

dscn3170.jpg | picload.org

Thats what I got.

(Yes, not perfectly paralell, I just noticed. I do have to manually press down on the tonearm, because of the "safety mechanism" these duals have where they won't drop the arm unless the turntable is spinning and the speed is perfect.)

The cartdridge is mounted pretty far at the front. It seems like i'd have to set it at the very top, since the stylus is sitting right before the destinated circle.

Edit2:
Even set at the very top it's just barely hitting the middle of those circles

also, that program by Conrad says I should have an overhang of "19.653" rather than 18

 

If you don't have enough slot length to get that overhang, change the parameters for lower overhang (use different alignment or change the inner/outer radius values). I tried it with Stevenson and it was under 18mm overhang, or Lofgren A with DIN for the radius.

 

Ok I ended up using Löfgren A with DIN grooves. almost exactly 18mm, so I guess that's what DUAL made their calculations on. Cartdridge still mounted at the very top, but if that's how it works...
Anyway, it worked like a charm. Thanks for your help