Do you know what's wrong with this picture?
Above is a photo taken of a Thorens td150 mk1 from an eBay auction. It is not the purpose of this article to insult the seller. He simply did not know any better. In an email to me he explained that he found the turntable in this condition at a garage sale. His purpose was to generally clean and lube the deck then sell it for a quick turn-over in the online auction. The purpose of this article is to make aware, to those who don't already know, that there is a huge fundamental error in the way this turntable is configured.
Q. so what's wrong?
A. A Thorens tp60 headshell is mounted to the original tp13 tonearm. The tp13 tonearm should be fitted with the tp50 headshell. Both tp50 and tp60 headshells feature the same coupler design and with the same pin patterns. They will mount. But you should not interchange these headshells.
Correct if like this: 
The tp13 (mk 1) with its tp50 headshell mounted.
But not like this:
The tp13 (mk 1) with a later tp60 headshell mounted.
The TP60 should be fitted to this arm:
The tp16 mk 1 and also to the similar Thorens tonearm, the tp11 mk1 (not shown)
Reason why?: Zenith angle. The tp60 headshell was intended for the straight armtube of the tp16(mk1) tonearm. The offset angle is built-in to the headshell itself. The earlier tp13 tonearm has the offset angle formed into the curved armtube. The matching earlier tp50 headshell, therefore, is "straight". When you mount the later tp60 headshell to the earlier tp13 tonearm you effectively double the offset angle. And, for you really stubborn eBay sellers, no amount of twisting the cartridge within its mounting will correct for this much error.
click on thumbnail to see full size image. 
Click on thumbnail to see an illustration of the use of a 2-pt.
protractor in use for tonearm alignment.
Btw there are other Thorens tonearms which use the tp50 headshell. these arms are the tp14 and tp25. Just like the tp13, you can actually mount the later tp60 headshell on these arms, but if you do you will double the zenith angle and make it impossible to align the arm/cartridge.
Q: So what if I get all the other alignment parameters within tolerance and just live with double the zenith angle?
A: Bad stereo separation. Poor tracking because of a huge tangency error. Potential groove damage to your records. Generally, less than optimal sound quality. Mis-tracking. Excessive side loading to the cantilever and its suspension within the phono cartridge. ...etc. Just don't.
