SDS speed control

This may be an irrelevant or stupid (or both) response, but make sure you are not using any type of battery-powered light source; it needs to be powered by AC to result in the necessary "strobing". How do I know? I tried a battery-powered fluorescent light for hours until I called VPI and they told me to use an AC-powered (plugged into the the wall outlet) fluorescent...DOH!

If the bars move counter clockwise the platter is slow, increase the frequency of the sds to correct. If the movement is clockwise then the platter is fast so reduce the frequency to correct.

If the rate of rotation of the bars does not change when you change the frequency of the sds then that would suggest the the frequency is not changing and something is wrong with the sds.

If you are changing by .01 hz it will take quite a bit to make a visible change on the strobe disk. Try changing the frequency by 5 or 10 hz and see what happens.

Shakey- Belt slippage doesn't have to be, "severe" to show with a strobe/disc and not everyone can discern minor speed/pitch variations aurally. The OP did say, "a slow spin to the right."

Thanks for all the advise/tips. I just got in the mail today a Keystrobe disc and associated Keystrobe Quartz strobe light. Will try it out when home from work. It all sounds good but I want to insure accurate speed with a proper strobe set up. Thanks again.

if your wooden/plastic motor spindle the belt touches is the wrong diameter the sds will be adjusted to a level it is not designed for and never settle down. this happened to me. vpi sent me a smaller diameter and cured problem

How does the table sound? If the table sounds alright, then perhaps you are using the strobe disc and light incorrectly. What are you using as a light source and strobe disc?

If your belt is slipping significantly; no amount of correction from the SDS will help.

I would think something that severe would be immediately audible....

Shakey

Have you changed, or applied talc to your belt & lubed the motor lately? Cleaned the circumference of the platter and pulley, with alcohol? If your belt is slipping significantly; no amount of correction from the SDS will help.

What strobe disc and light are you using? The VPI supplied strobe disc is pretty much useless, and I didn't have much more luck with a decent quality Hansen strobe disc and a "neon" light until I got the KAB Speed Strobe and used the quartz illuminator to determine the platter speed. You really need to be able to see the strobe disc markers clearly, which could be difficult without proper light.

Why not call or E-mail VPI....it sounds like something is wrong.