TD160 platter not spinning true. A spring or bearing issue?

music box
johnnyboy114
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Re: TD160 platter not spinning true. A spring or bearing issue?

Post by johnnyboy114 » 13 May 2019 19:45

Ah. That was done by Alan above. He took it and measured the run out on a micrometer while spinning on a correctly set up host turntable and the sub platter is well within Thorens tolerances apparently. And runs competent true on his base unit.

Which is why it makes this all so confusing!

nezbleu
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Re: TD160 platter not spinning true. A spring or bearing issue?

Post by nezbleu » 15 May 2019 19:24

If the sub-platter is OK and spins true on a different turntable, then the issue is your turntable. Lock the sub-chassis somehow (maybe use the transit screws with so spacers to hold the sub-chassis in the "right" position wrt the main chassis). Test for true spinning as suggested by Alec. If it still wobbles then the issue is in the main bearing. If it doesn't, then the sub-chassis must be wobbling when the platter turns. Once again this would imply an issue with balance of the platter/sub-platter assembly, or some external irregular force applied to the sub-chassis.

To summarize:
Original platter assembly wobbles in your turntable.
Original sub-platter does not wobble in other turntable.
Other sub-platter wobbles in your turntable.

So the issue must be in your turntable. There are two loosely coupled parts to the turntable, the main chassis and the sub-chassis. The only source of energy applied to this system comes from the motor (fixed to the main chassis) through the belt to the sub-platter which is mounted in the sub-chassis. If we know the sub-platter is fine, then any unusual movement is happening EITHER between the platter and the sub-chassis OR between the sub-chassis and the main chassis. If the platter is moving wrt the sub-chassis then the main bearing is faulty (because it is the only thing that fixes the position of the platter wrt to the sub-chassis). If the platter is not moving wrt the sub-chassis, then if the platter is moving wrt the main chassis then the sub-chassis must also be moving wrt the main chassis, in some periodic manner.