SDS speed control

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

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.