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Sansui SR-313 too fast.

Madeline12

Madeline12

Super Member
Hello everyone.

I was hoping a belt replacement would help with this one. I had a loose belt before, but when I brought it in to a local shop to see if there was a hum (refer to my previous thread) suddenly the turntable was moving too fast, even with a loose belt. I’m wondering if something got jostled when I was driving there, because it used to be perfect speed. Anyways, I bought a belt replacement for it from Bob’s Vintage Electronics. Still, same problem. It’s improved, but it’s still too fast. Is there a way I can adjust this mechanism in order to get the correct speed? That is if it’s to be advised. It starts getting to the right speed when I adjust the lever for speed selection. Any help is appreciated.

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On the vinyl engine site, there is a service bulletin that may help. The first thing I would do I did is lubricate the capstan and motor, and see if you can find the length of the belt through a google search. The thickness of the belt is also important, and I have seen thickness cause speed changes.

Some belt drive turntables are very difficult to find the right belt. Not sure about this one. I think I had the 222 and the 323. But that was a while ago. If you can find any adjustment potentiometers on the boards, it may be dirty contacts. Deoxit

I’m sure others will be around who know more on your model.
 
BilboBaggins said:
On the vinyl engine site, there is a service bulletin that may help. The first thing I would do I did is lubricate the capstan and motor, and see if you can find the length of the belt through a google search. The thickness of the belt is also important, and I have seen thickness cause speed changes.

Some belt drive turntables are very difficult to find the right belt. Not sure about this one. I think I had the 222 and the 323. But that was a while ago. If you can find any adjustment potentiometers on the boards, it may be dirty contacts. Deoxit

I’m sure others will be around who know more on your model.
Click to expand...
Thank you, I figured BVE would be a good bet, but it’s definitely possible it’s the wrong belt I supposed. Not too concerned, this isn’t a knock against the business FYI. I will take a look internally, though I don’t remember seeing any pots.
 
Not much on there is there? Just that one board that I can see. Funny. Take a look at the service advisory. Probably the belt. I remember trying three belts before I found the right one for one I had. Now I have 6 or 7 belts of different sizes I can try. Left over from past mistakes. I recommend you clean and lube the capstan shaft and the platter receptacle. Be very careful not to get any lube on the belt, platter, or the capstan in the belt path.
 
Very good! I didn’t look it over in detail enough. Yes, you are right. That is the schematic for 120 v. I can’t see a cap going to Thebes motor will cause the speed to be faster or slower. I think that cap gives a power boost for motor startup.
 
The motor capstans on many belt-drive tables have barrel shaped sections where the belt rides. There is usually a provision to "tilt" the motor, which changes where the belt rides on the capstan; on the fatter middle part speeds you up, on the thinner upper or lower areas slow you down. Usually a minimal change, but generally enough to get you dialed in.
 
arts said:
The motor capstans on many belt-drive tables have barrel shaped sections where the belt rides. There is usually a provision to "tilt" the motor, which changes where the belt rides on the capstan; on the fatter middle part speeds you up, on the thinner upper or lower areas slow you down. Usually a minimal change, but generally enough to get you dialed in.
Click to expand...
I’m sorry, I’m unsure of what you mean by thinner parts. I’ve pictured the capstan in my original post, however it seems the thinnest part it the middle. Am I incorrect?
 
It is hard to see, as the speed change lever is mostly blocking the view. If you look at where the belt actually rides for each speed, is the shaft barrel shaped? I believe that the thinnest part that you are referring to is just the space between the two speeds.
 
Here is a close-up photo (really bad) that I snagged off the net that shows the two barrel shaped areas where the belt rides:

images
 
arts said:
Here is a close-up photo (really bad) that I snagged off the net that shows the two barrel shaped areas where the belt rides:

images
Click to expand...
It’s similar for sure, but a slightly more gradual transition from the top thinner part to the bottom thicker part. I’ll get a pic momentarily.
 
Nothing in the circuitry will have any bearing on speed. It's an AC synchronous motor so it relies on the 60hz of the line current to get it's speed.

There are really only 2 ways to slow the platter down. One is the correct belt. Thickness does matter and width will too to some extent, especially since it impacts where it rides on the barrel shape. The other method would be to change the ratio of size of the motor capstan to the rim on the platter. The easiest way to do this is to add layers of electrical tape to the platter. It sounds a bit hokey but it works.

How much are we off on speed anyway?
 
Hey everyone, sorry it took so long to get back to you guys. Got caught up with work. Anyways, the turntable is moving 4.5% fast, and here’s a pic of the capstan.

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Think I figured it out, the capstan is too close to the center of the platter, the motor is a little wobbly. I bet that’s it. I asked someone personally what could cause this, and he said the grommets are probably ruined. Anyone know where I can get new ones?
 
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