As the title says the belt of my TD125 MKII slips off the motor pulley on startup. Besides this recent nuisance the table works flawlessly.

It is an original purchase by me back in 1975-76 which I used extensively and had it looked at a few times since then for minor maintenance including belt replacement about five years ago (if memory serves me correctly).

I'll try and post a pic or two of the table itself along with the pulley.

Any thoughts as to what may be causing this?

Thanks in advance.

Maybe the belt is running on the wrong side or maybe there is some grease in the inner metallic plate or the TT is not leveled properly. At least, three easy points to check.

Turn the platter upside down and watch the belt on the pulley during startup. My guess would be the little adjustment spring on the pulley mount. When the motor starts up, the belt is running either up or down on the pulley and pops off. There is a "sweet spot" that you have to dial in exactly, and it requires some measure of periodic adjustment. I ended up machining a new pulley wheel out of delrin for mine.

rooster.

Take the belt off and clean it, then clean the motor pulley and the inner platter thouroughly. Use 91% Alcohol and carefully just enough to clean things up. Put the clean belt in a plastic bag and pour in some baby powder. Shake it up to coat the belt. Take the belt out of the bag and without getting it covered with fingerprints wipe off the excess powder with a paper towel. The belt will now appear a dusty gray color.

Install the belt and it should run fine. It will slip at first when you start the motor but will grip and run fine. If it has stretched and continually slips or runs slow flip the belt where it meets the pully. This will tighten it some, enough anyway to determine if you need a new one.

Buy a new belt! Yours is stretched out.

While you are waiting for a new belt, try giving the belt a twist when mounting it and it may run right.

Take the belt off and clean it, then clean the motor pulley and the inner platter thouroughly. Use 91% Alcohol and carefully just enough to clean things up. .....

Is it OK to use 91% alcohol on rubber?

Is it OK to use 91% alcohol on rubber?

This one time won't hurt. You should be buying a new one anyway. What I have done here is attempt to fix your immediate problem.

Is it OK to use 91% alcohol on rubber?

I'd use it on the pulley but not on the rubber.

Have you been having sustained humidity and is your turntable in an environment without central air conditioning? iI so, the problem could disappear when the weather changes.
If you can start the platter spinning and it'll stay spinning, the belt is on its way out but a change in the weather may save you for another (almost) year.

I like that turn the platter upside down suggestion. I've learned something rooster18.
Thanks

Have you been having sustained humidity and is your turntable in an environment without central air conditioning? iI so, the problem could disappear when the weather changes.
If you can start the platter spinning and it'll stay spinning, the belt is on its way out but a change in the weather may save you for another (almost) year.

I like that turn the platter upside down suggestion. I've learned something rooster18.
Thanks

No sustained humidity to speak of.

Please elaborate on "If you can start the platter spinning and it'll stay spinning, the belt is on its way out".

I also like the upside down platter suggestion (thanks rooster18), I'll give it a try. In the meantime I'll be ordering a new belt (or two).

Thanks everyone.

sounds like you need a belt. having to turn that huge platter mass means the need for a secure transfer of torque.

If you get a new belt - make sure its a genuine thorens. Otherwise the new belt will get tossed off the motor and or platter. The thorens have a specific texture and elasticity which generic belts to not. I think Acoustic Sounds carries them.

I think I got my TD125 MKII belt from Q Audio. It's the real deal.

rooster.

sounds like you need a belt. having to turn that huge platter mass means the need for a secure transfer of torque.

If you get a new belt - make sure its a genuine thorens. Otherwise the new belt will get tossed off the motor and or platter. The thorens have a specific texture and elasticity which generic belts to not. I think Acoustic Sounds carries them.

Acoustic Sounds does carry them, the OEM belts are slightly narrower than the aftermarket, so the speed will not be correct with an aftermarket belt.

First I heard this one...:scratch2:

First I heard this one...:scratch2:

Keep your eye on the archives, it's pretty well documented problem. :thmbsp: