[78-L] Co 113a Alignment issues

Iñigo Cubillo ice261263 at gmail.com.invalid
Sun Jan 15 07:55:46 PST 2017

Ron, and all:

I've taken several photos, as best as I could, to illustrate the geometrical 
issues with the Co 113a tonearm. The images are self-explainig, and I tried 
my best to underlay a paper with master lines traced so the real thing can 
be examined. I also show the 65 degree (more or less) achieved due to the 
self-made rubber back joint. There is also a typical geometrical diagram 
showing the general principles of tonearm alignment. The photos show how the 
Co 113a tonearm is aligned when a 65 degree zenith is fixed.

Of course, the solution for this case is to provide an inwards angle to the 
soundbox (what is the same in the end, more offset distance). Otherwise, the 
distance between the spindle and the tonearm pivot should be modified, but 
this implies modifying the motorboard, etc.

Thus, by trial and error one can try smaller modifications to improve the 
tracking as possible, by a wedged joint, a trunnion connector between 
soundbox and tonearm, etc. These things would not seriously modify the 
machine while improving the tracking error.

Here is the link to the images;


Hope this helps...

Inigo Cubillo 

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