Pioneer PL-112D Turntable too fast.....Help!

IowaFightFan

AK Subscriber
Subscriber
I have a Pioneer PL-112D belt drive turntable. There are no manual speed adjustments, like an automatic deck will have. This is spinning at approximately 34.4 - 34.8 RPM, which is noticeable on some songs.

I took the motor apart, cleaned it (it had been overlubricated it looks like) and then put a small amount of turbine oil in the lower bearing, as well as a small amount at the top of the shaft (which should make its way into the upper bearing).

I took the spindle shaft out, cleaned it. Cleaned the well that the shaft goes into, including removing the small ball bearing and cleaning it. I put a drop of oil into the well, put the ball back in and the spindle shaft back in.

Removed the belt. Cleaned it and the inner rime of the platter (where the belt rides) with alcohol. Cleaned up the motor pulley as well. Everything is cleaned, oiled and seems to be working great, with the exception of it being too fast.

Any ideas?
 
I have a Pioneer PL-112D belt drive turntable. There are no manual speed adjustments, like an automatic deck will have. This is spinning at approximately 34.4 - 34.8 RPM, which is noticeable on some songs.

Any ideas?

Some belt drive turn table needs a belt of the proper thickness as well as the proper length.

Try the one from the following site, they are generally right on. :thumbsup:
http://www.vintage-electronics.net/pioneer-pl-112-belt.aspx

If not you should be able to return it. :idea:
 
I have the same turntable and had exactly the same problem with the belts available from ebay. I actually tried 3 different suppliers there, two of the belts made the turntable run too fast and one too slow. There no motor adjustments (it's a synchronous motor, tied in to line frequency) Finally found the solution which is a belt of the right thickness sold by Thakker in Germany. https://www.thakker.eu/en/ If I remember correctly it took about 3 weeks to get the belt and it was a bit more expensive than the ones at ebay but the speed is dead on.
 
I'm almost positive that it is the belt, based on my recent experience with a Yamaha YP-B4. When I bought it, it ran about 32.8 rpm. I bought a new belt, and it runs right on speed now. I should probably take the motor apart, as there's some kind of noise/vibration happening somewhere with the belt on it.
 
Yes, It's pretty much always the belt. A tried and true (and generally frowned upon) cheat is to apply nail polish to the pulley, one layer at a time, which will slow down the speed.
 
A layer or two of electrical tape on the platter will slow it down. That is good fix if you cannot find the correct belt.
 
I have the same turntable and had exactly the same problem with the belts available from ebay. I actually tried 3 different suppliers there, two of the belts made the turntable run too fast and one too slow. There no motor adjustments (it's a synchronous motor, tied in to line frequency) Finally found the solution which is a belt of the right thickness sold by Thakker in Germany. https://www.thakker.eu/en/ If I remember correctly it took about 3 weeks to get the belt and it was a bit more expensive than the ones at ebay but the speed is dead on.
I know belt drives to bring benefits to the table, but this is one of the reasons I abandoned belt drive back in the mid 70's and only do direct drive. Though both systems can bring their own strengths to the table and some EXTREMELY expensive and good turntables use belts, I just like not having to even think about it. I can drag a discwasher across my record, really slowing it down, and I don't have to worry about stretching or breaking a belt. I just don't like having to maintain stuff unless it's the only way.

And to be clear, all three of my current DD turntables are dead quiet.

Now, if you'll excuse me, my car has 100,000 miles on it, I think it's finally time I changed the oil. :D
 
Yes, It's pretty much always the belt. A tried and true (and generally frowned upon) cheat is to apply nail polish to the pulley, one layer at a time, which will slow down the speed.

This pulley?
IMG_20190210_150920208.jpg

Why would that slow down the speed of the platter?
 
There must be a couple dozen threads on this subject, most of them on this very same model. Belt thickness changes effective radius causing speed error. FWIW I totally agree with RobRoy after having gone through this time and time again. Last couple of times I just wrapped the platter with tape after three or more attempts with what various eBay sellers insisted was supposed to be "THE correct belt for Pioneer belt drive tables" didn't work. Never tried Thakker though, if anyone's going to get it right he will!
 
Yes, It's pretty much always the belt. A tried and true (and generally frowned upon) cheat is to apply nail polish to the pulley, one layer at a time, which will slow down the speed.
Thinking about your post, wouldn't an increase in the diameter of the pulley (by layering nail polish) speed up the turntable even more? After all, when switching from 33 to 45 the belt is switched from a smaller diameter to a bigger diameter on the pulley. Now the other suggestion of putting tape around the platter would logically work to slow down the platter rotation speed.
 
Thinking about your post, wouldn't an increase in the diameter of the pulley (by layering nail polish) speed up the turntable even more? After all, when switching from 33 to 45 the belt is switched from a smaller diameter to a bigger diameter on the pulley. Now the other suggestion of putting tape around the platter would logically work to slow down the platter rotation speed.

Exactly! Increasing the diameter of the small drive pulley will speed the platter up. Increasing the diameter of the large platter belt rim will slow the platter down, like @peerson suggests by adding a layer of tape to the platter rim. Unless the suggestion is to put a layer of nail polish on the platter rim?? Which I wouldn't do. Actually, I wouldn't do either, no guarantee that you could get a uniform thickness coating of tape or nail polish around the circumference of the ring.

The problem and solution seems to be finding a belt of the right thickness. The drive pulley/capstan is a very small diameter, and it doesn't take much of a difference to have a noticeable effect on speed. If the belt is too thick, it changes the radius at the drive capstan enough to increase the speed. My first turntable was a PL-112D. Long gone now. I've never been able to find the belt thickness specification.

Here's an example (pulley diameters are in mm, pulley 1 is the small pulley, pulley 2 is the platter belt rim, assume drive motor runs at a constant 1,000 RPM)
Drive pulley is 6.6mm diameter. Solve for platter speed = 34.6 RPM
Platter_Too_Fast.jpg
Increase the drive pulley diameter by a mere 0.2mm to 6.8mm and the platter is now running at 35.6 RPM
Platter_Speed_Faster.jpg
 
I have the same turntable and had exactly the same problem with the belts available from ebay. I actually tried 3 different suppliers there, two of the belts made the turntable run too fast and one too slow. There no motor adjustments (it's a synchronous motor, tied in to line frequency) Finally found the solution which is a belt of the right thickness sold by Thakker in Germany. https://www.thakker.eu/en/ If I remember correctly it took about 3 weeks to get the belt and it was a bit more expensive than the ones at ebay but the speed is dead on.

I tried one belt from Ebay, had no luck (was still too fast, as well as kept slipping off when going from 45 RPM to 33 RPM), so I ordered from thakker also. It ended up being about $17.50 I think, so not too bad. I will report back once I get it and let everyone know how it worked out.

Thank you all for your responses!
 
I tried one belt from Ebay, had no luck (was still too fast, as well as kept slipping off when going from 45 RPM to 33 RPM), so I ordered from thakker also. It ended up being about $17.50 I think, so not too bad. I will report back once I get it and let everyone know how it worked out.

Thank you all for your responses!

Hopefully it'll work for you as well as it worked for me. One thing I recommend is cleaning the pulley really good. The table I bought on ebay had all kinds of crusties on it. It had probably been siting on some closet shelf or garage for the last quarter century or so no surprise.
 
I cleaned everything really well. I had seen lots of pictures and videos where that motor pulley had remnants of old belts that had adhered to them when the decks sat around for years. This one was well cared for, in good shape. I got it just because the speed was off.

I hope the belt works too! It was the most expensive, but if it fixes it, well worth it!
 
I have the same turntable and had exactly the same problem with the belts available from ebay. I actually tried 3 different suppliers there, two of the belts made the turntable run too fast and one too slow. There no motor adjustments (it's a synchronous motor, tied in to line frequency) Finally found the solution which is a belt of the right thickness sold by Thakker in Germany. https://www.thakker.eu/en/ If I remember correctly it took about 3 weeks to get the belt and it was a bit more expensive than the ones at ebay but the speed is dead on.

Got the belt from Thakker yesterday. Put it on and both the 33 & 45 RPM speeds were pretty much dead on! Not to mention, it switched from 33 to 45 RPM without slipping off the motor pulley. The cheaper Ebay belt kept slipping down the motor shaft when I switched from 45 RPM to 33 RPM.

Took a few weeks and ended up around $18 shipped, but the Thakker belt is definitely the way to go!
 
Got the belt from Thakker yesterday. Put it on and both the 33 & 45 RPM speeds were pretty much dead on! Not to mention, it switched from 33 to 45 RPM without slipping off the motor pulley. The cheaper Ebay belt kept slipping down the motor shaft when I switched from 45 RPM to 33 RPM.

Took a few weeks and ended up around $18 shipped, but the Thakker belt is definitely the way to go!

Glad it worked as well on your turntable as it did on mine. Before I read up on it I had not realized the importance of the thickness of the drive belt because I didn't understand the physics of the pulley/belt relationship. I had always assumed that a belt works the same way as the idler wheel on an idler turntable such as my Dual 1019 where the diameter of the idler makes no difference as long as it has good contact with both the motor pulley and the platter. On a belt drive the center of rotation moves with the thickness of the belt so that a thicker belt results in an effectively greater diameter on the drive pulley. Greater diameter> greater speed. That's why the 45 RPM pulley has a bigger diameter. An that's why all of those supposedly correct belts from E-bay don't work right - wrong thickness.
 
All that comes into contact with either pulley is the inner surface of the belt. The outer surface doesn't drive anything so the darn thing could be a half inch thick and it would not change the formula for determining speed. I'm not saying that it belt thickness isn't a factor. I am saying that the reasons stated don't have valid reasoning behind them. Now, if you were to say that there is a minute amount of slip on the drive pulley which changes with different thickness belts, that is logical. There is very little actual surface area on the drive side compared to the driven side, so any wear on the drive pulley will show up as a reduction in output speed. That would be where the building up of the drive spindle could put the machine back into spec.

My guess is that belt tension is the determining factor. Too thick of a belt equates to higher tension and less slip, causing a slightly higher speed of the platter. Too much tension in any belt drive puts strain on the bearing surface of the drive shaft resulting in premature motor bearing or drive bearing failure. My guess is that somewhere some engineering data exists that states a proper belt tension and maybe even some numbers defining an acceptable belt stretch range at that tension. Without those numbers, buying non OEM belts is just a roll of the dice.
 
Back
Top Bottom