[78-L] Co 113a Alignment issues

Ron L'Herault lherault at verizon.net.invalid
Sun Jan 15 09:50:37 PST 2017

Great set of pictures, Inigo.  The movment of the tone arm and position of
the needle are never ideal over all the record, correct?   Ideally does the
needle meet the center of the spindle if possible or is it supposed to be
beyond the center spindle?   Since the needle starts out spherical and is
constantly being modified by the abrasive nature of the record surface, does
this action correct for some physical tracking error?

Ron L

-----Original Message-----
From: 78-l-bounces at klickitat.78online.com
[mailto:78-l-bounces at klickitat.78online.com] On Behalf Of Iñigo Cubillo
Sent: Sunday, January 15, 2017 10:56 AM
To: 78-l at klickitat.78online.com
Subject: Re: [78-L] Co 113a Alignment issues

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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