Slipping Belt on Thorens TD-150

I have a modded Thorens TD-150 with a MusicHall Cruise Control 2.0. The issue I'm running into is the best is slipping when you turn the TT on. Any ideas on how to improve the "traction" of the belt? Thanks!
Sounds as if the pulley and platter where the belt touches will need some cleaning, and then the problem is likely that the belt is stretched and dry.

Thus the belt needs a bit of ’renewal’.

You can buy a small container of rubber renewal fluid and then soak the belt in that, but only after you clean it.

A second trick I like to use is to buy a 3000 or 2500 or 2000 grit sandpaper (higher is better) and lightly sand the surface of the belt, with some slight low pressure pulls through a folded bit of the sandpaper sheet. do this minimally, kinda thing.

the rubber is drying out so alcohol cleaning is the wrong direction.

First the pulley and sub-platter cleaning, more the pulley than sub-platter.

then the belt sanding, belt cleaning then rubber renewal.

Or just buy a new belt.

If trying to get it done now, then the pulley cleaning and sanding as the rubber renewal fluid is not going to be found in many places. Mostly just electronics component supply shops.

The light sanding renews the surface, and gives you better grip and slightly better flexibility. It may be enough to get by for the moment.

Be careful with the sanding, with regard to potentially creating an uneven thickness of the belt. Wow and flutter will go up if handled incorrectly with too much force and too much sanding. This may stretch the belt even more (low chances) if the job is aggressively handled (higher chances). Try to not round the edges unevenly.

Eg, Linn and others sand their belts to a precise surface characteristic and a precise uniform thickness and even slope profile (cross section view), depending on the manufacturer of the belt and table. This is why a cheap inexpensive replacement belt will work for a Linn table but always move toward buying the proper original Linn sourced table belt.

Whatever the table..if it is a performance table and it is known to employ special or well made belts.....try to get an original or correctly made belt for it. Considering the cost differences, $20-40 more for the correct belt is worth it as the percentage increase in performance can be at least at few percentage points in one’s estimation, if not more. The gains are minimally priced bargains. ’No-brainers", of a sort.
@zavato i have an older and a newer belt. The newer one is an original Thorens belt. This one doesnt slip as much when starting (it is smaller) but it did drop to the lower part of the pulley causing the speed to bump to 45.

My table is modded to remove the metal guard, and leverage a MusicHall Cruise Control 2.0 to manage the speed.

Nice try, but as you can see, the OP doesn’t respond to involved posts that may require effort on (his) part.

Next he’ll want us to evaluate how a certain lp sounds on his system?

#been here before
@slaw  on the contrary actually... there are certain requirements that I am trying to work around, hence why some actions are not feasible. That said, regarding my other post, I will be stiffening the floor.

Regarding this post, I have two belts, different sizes, and looking for confirmation that this is not a specific problem to my TD-150.

One of the belts is brand new, one is 3 years old. The new belt is tighter than the older belt (obviously). The newer belt slips to the lower part of the pulley.

Sanding the belt is a solid idea that I will be trying this evening if nothing else improves.
@teo_audio I have cleaned the pulley and the inner platter with alcohol and ensured that there is no oil residue as that can wreck havoc on the belt's ability to hold.

The reason why I didn't reply specifically to your post yet is because I haven't had a chance to try a few of the other steps.

Thanks for your involved post, very great insight there.
The traction on a flt belt and a crowned pulley has to be controlled and also that there will be wear, and thus a slicking or shining of the surface of the belt and the pulley, but obviously the belt carrying the majority of the wear and becoming slick. Which only exacerbates the problems, and can eve change the patterns of the different motional/loading components of the relationships.

Thus the lowest level of wow and flutter and thd, etc, will come about with a certain level of loading of the system, which is carefully adjusted by the given designers of said system. Overall, the system is more complex than it initially looks. The belts are allowed wear range and the distances and and tension(s) between components are carefully adjusted. Certain derometers and constitution of the rubber belt and so on, are carefully selected.

For example, with a crowned pulley, a certain scalloped or hollowed out characteristic of a belt cross sectional profile might work better than a purely flat belt. More perfected speed, lower wear? Depends.

While just any combination of these parts will make for a minimal ’turntable’, best results are invariably down the complex analysis path.

This is why for example, with a Linn LP12..there is only one real choice regarding getting what you are paying for, and that is to use a Linn sourced belt.

This is getting into the nitty gritty of it, though, so one’s own priorities and limits in involvement is the deal. As per norm.
New belt fixed the issue, also tuning the pulley screw to better align the pulley. Only a small amount of scrubbing on startup now.