Speed Control on Quiet Spindle

Anyone having trouble with the speed control on the quiet spindle. I had the spindle running, assembled my case and it wouldn’t run. Redid all the connections and the spindle ran. Shut it down and turned it on, and the spindle would not run. Frustrated, I thumped the speed control on the side of the case. It worked. How can a solid state unit work when you thump it?

I also threw a nasty arc from the speed control capacitor to the frame a couple of inches away.

I am replacing it, but has anyone else seen this kind of issue?

Great answer. I didn’t think about it. I may be able to fix the sucker. Thank you

Are able to control the new spindle via pwm?