Measuring TT Speed

WoW is every rotation, fludder is intermittent? Or is that backwards..
Been a while.. If the belt is in a grove and the NEW one is just a hair to wide, as the belt comes off the pully and out of the grove, BOING! it snaps out..

Make sure there is not a wide spot. Mark the wide spot, trim if needed (with sandpaper), and re-powder the belt.. BUT wipe and clean the pullies.. DON’T forget.. A sticky spot on a pully, can drive you nuts...
Slipping belt, whole different thing, touch the platter it stops... Slow startup.. la te da.

Regards

Hi, jsman,
What are you using for a light source to check the strobe disc? If the light isn't stable you'll get strobe "bounce".
Tom

I bought years ago a Sutherland Time Line that checks TT speeds VERY accurately. If you can find an Agon member in your area to borrow one that would be what I suggest. If you live in the Boston or Southern NH area PM me. 

Mijostyn, With much respect, especially as I have never used the particular application you recommend, RPM, cell phones are notoriously inaccurate for measuring TT speed.  If the strobe is wavering back and forth, it means something. Sometimes that can be an optical trick due to flickering of the strobe light or see below. So long as the strobe markings do not move definitively in one direction or the other, the problem may lie with the strobe.  The OP does not say what strobe he or she is using.  For me, the only strobe worth having is the KAB product, which comes with a battery-powered strobe light that is constant in its pulse and a larger than average diameter strobe, so the markings are moving at a faster speed due to a further distance from the center of rotation, compared to the average strobe disc.  Any strobe light that plugs into the wall is subject to the minute variations of the AC frequency and could give the phenomenon the OP is talking about. Unfortunately, the KAB kit with strobe disc and battery-powered strobe light costs $100, but is well worth it in my opinion.

Reality check: no belt, motor, AC, or anything else gonna make the lines "bounce back and forth" the changes in platter speed for that to happen are just insane, beyond the torque of the motor, and the OP wouldn't even need a strobe the table would be totally unlistenable. 

Its just light hitting the strobe bars at the wrong time. Ignore those, concentrate on the average, you'll be fine.