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VPI Scout running FAST...help?

Ladies and Gentlemen-

For your consideration, I present my very first world but very real audio problem.

Proud (sorta) second owner of a VPI Scout One. 11.5 Acrylic platter, 600rpm motor. Approx 3 years old, appears very little previous use.

At the present, the table is running at a steady and consistant speed of 34.6 and 47.1. I have tested the speeds using my ears (songs sound too fast), a strobe, the old fashioned counting RPM's over a 3 minute period, and even so far as to have a friend bring over a centerfuge calibrator from a medical lab. So I am certain that these are the speeds it is presently running.

Things I think I have ruled out:

Belt is new, but not brand new

Table is on a flat, level surface

Pulley is attached soundly in the motor

The reported speeds are at the top "rung" of the pulleys, I am aware that the higher up the pulley the belt is, the slower the platter turns.

Outlet power is ok, I have tested the table on multiple outlets and it is the same, also, my older Pro-ject table ran a consistant 33.5 on the very same outlet.

This is where I run out of ideas. I have placed an e-mail and call to VPI, but have not heard back yet. Anyone have any ideas? Goin crazy here...

Thanks in advance-
thebambino
dtc's avatar
dtc
1,047 posts
 
For reference, with the 600 rpm motor, I was at the very top of the pulley to get 33.3. When I changed to the 300 rpm motor I got much better speed control.

The 600 rpm motor uses a pretty small pulley. The 300 rpm motor uses a significantly larger pulley. For reference, my 300 rpm pulley is 1 and 1/4 inches across the top. The 600 rpm pulley is significantly smaller. Do you have the right pulley? I believe there is also a different pulley for the 12" platter versus the 11.5" pulley.

When using the 300 rpm motor, a capacitor needs to be changed. Is it possible that the original owner changed the capacitor?

If possible, I would ask the original owner if they had made any changes to the motor, capacitor, pulley or platter.

It sounds like you may have the wrong pulley. I would ask VPI to send you the right pulley for your platter/motor. It may be that the setup has never been right.

You are not the first to have this problem. Rest assured, you will get it right.
thebambino OP
19 posts
 
Thanks DTC- my pulley is well under 1.25 inches at the top, more like .5 inches...i also believe you are correct, it would only make sense that there would be a slightly different sized pulley for the 11.5 inch platter vs the 12 inch platter for the 600 RPM motor.

I don't think the original owner made any mods that I am aware of, in fact, I think he's been running this thing fast for the three years he owned it...no wonder he went back to CDs.

Is the pulley swap pretty easy once I get it? I'm no mechanical engineer, but not a total dunce either.
dtc's avatar
dtc
1,047 posts
 
Changing the pulley is trivial. There is a small hex set screw at the base of the pulley. You just need the right size, readily available at a hardware store if you do not have one. Take a look and you will see the set screw.

I remember a similar thread a while ago and the problem was a wrong size pulley. I would ask VPI to send you one for the 11.5 inch platter. I think that will fix the problem.
dtc's avatar
dtc
1,047 posts
 
FYI - I found the 300 rpm motor a significant upgrade. With the 600 rpm, the belt keep slipping and the speed was variable. With the 300 rpm with the larger pulley, the speed really locked in. Not everyone agrees, but I found it a real improvement. You do need to change the pulley and the capacitor in the motor box, but it is a relatively easy change.
pbnaudio's avatar
pbnaudio
1,613 posts
 
As mentioned above it sounds like you have a motor pulley for a 12 inch Platter
and are running it on a 11.5 inch Platter, it will give exactly the deviation you
mention.

The math is pretty simple, 12 / 11.5 x 33.333 = 34.78 rpm

The speed of the motor is determined by the number of poles in the motor
combined with the line frequency it attached to, it will only deviate if the line
frequency changes. Also a less than optimal drive system will only cause the
platter to run slower due to slip, it will never run faster only a higher line
frequency can cause that.

Good Listening

Peter
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