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New Jelco TK-850S Tonearm

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Posted on October 17, 2020 at 18:47:43
joey1127
Audiophile

Posts: 382
Location: Sacramento, CA
Joined: June 25, 2007
Hi All,

I recently upgraded an older Jelco SA-750D tonearm to the NEW Jelco SA-850S. Question...The older Jelco arms indicated the stylus tip to be placed 52mm from the back of the washer on the Headshell to the stylus tip for proper overhang. However, on the new arm which now uses a Baerwald geometry, they don't specify this measurement... Anyone know if the new arm can be setup with the stylus 52mm from the collar on the back of the Headshell to the stylus tip or has that parameter changed now?

Thanks,

Joey1127

 

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RE: New Jelco TK-850S Tonearm, posted on October 17, 2020 at 19:17:18
John Elison
Audiophile

Posts: 22997
Location: Central Kentucky
Joined: December 20, 2000
Contributor
  Since:
January 29, 2004
I don't know the answer to your question, but I would recommend always using an arc protractor to align your cartridge for the most accurate alignment. The beauty of an arc protractor is that it's easy to adjust overhang so the stylus follows the arc and then you know that overhang is set correctly. After that, it's a simple matter of adjusting offset angle at either of the two null-point alignment grids for a perfect alignment. After setting offset angle, go back and make sure the stylus still follows the arc exactly and you're done.

You can print your own arc protractor using Conrad Hoffman's Custom Arc Template Generator for Phono Cartridge Alignment. You can find Conrad's arc protractor printing program at the link below:

 

RE: New Jelco TK-850S Tonearm, posted on October 17, 2020 at 19:21:01
joey1127
Audiophile

Posts: 382
Location: Sacramento, CA
Joined: June 25, 2007
Yup, have one already...and have the Hi-Fi News & Review test record as well.

Thanks,

Joey1127

 

RE: New Jelco TK-850S Tonearm, posted on October 18, 2020 at 07:16:27
tketcham
Audiophile

Posts: 5927
Location: East of the 100th meridian
Joined: March 21, 2005
Contributor
  Since:
October 1, 2005
Hi, joey1127,

Since the alignment geometry has changed I wouldn't expect the previous stylus overhang measurements to be the same. I would just ignore the old setup instructions and align your cartridge to the Lofgren A (Baerwald) geometry.

Tom

PS: I agree with John E. on the Conrad Hoffman arc template, it's a great way to align a cartridge. Enjoy that new tonearm!

 

The flange/stylus distance remains the same, posted on October 21, 2020 at 16:22:34
flood2
Audiophile

Posts: 2164
Joined: January 11, 2011
The effective length and offset have changed due to the revised geometry which requires a new arm tube, but the point of the detachable headshell is that the flange/stylus distance can remain the same with the arm tube accommodating the change in geometry.

Given the tolerances in manufacture and possible shift in pivot position with respect to the intended design value for pivot/spindle distance, your suggestion to use suitable tools rather than taking things on faith is most sensible!


Regards Anthony

"Beauty is Truth, Truth Beauty.." Keats

 

RE: The flange/stylus distance remains the same, posted on October 21, 2020 at 17:41:15
tketcham
Audiophile

Posts: 5927
Location: East of the 100th meridian
Joined: March 21, 2005
Contributor
  Since:
October 1, 2005
If the stylus ends up at the same position relative to the headshell as described in the original instructions, all the better I guess. At least it will be at the right position for a proper Lofgren A alignment if you use a protractor/template. :-)

Tom

 

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