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Mounting a Jelco Tonearm

This is from a good friend of mine who is having a dilemna mounting a Jelco Tonearm.  I hope someone is able to help:

" I've been trying to determine a foolproof method for accurately locating the hole for a tonearm in a plinth.   I think the pivot to spindle distance or the total effective length provided by Jelco is just wrong.    Everytime I mount this thing it seems like it's not quite in the position it should be so the cartridges sit 1) in the middle of the headshell and 2) line up nicely with the alignment grid.  I think one of the numbers is wrong. But which one, and by how much?


I actually have one of those Dennesen Soundtracktors.   Do you remember those?  They are basically an older, plastic version of the expensive, but very nice aluminum Dr. Feikert one.


There's got to be a simple, logical way to work this out.  


It's amazing I can't seem to find information on the Internet about this.  I wonder what audio shops do?"

Thanks in advance for your comments,

Louis


128x128lou_setriodes

Showing 1 response by helomech

helomech
1,525 posts
 
I'd post this question on Audio Karma or Vinyl Engine, where there are larger DIY communities. I haven't mounted a Jelco, but have thoroughly read up on the process as it applies to Thorens tables. This is the first I've read of any discrepancies with the published length specs. However, when it comes to their effective mass, it's a mystery, no one agrees.

Whether a cartridge sits in the middle of the hesdshell is irrelevant. What is important is that it can align to both null points on a two-point protractor, or in your case, align to the grid with the arm/spindle jig in position. Carts and stylus' come in various lengths, so focusing on the middle of the headshell will only lead you to the mad house.


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