I acquired a Delta 3hp 240v Unisaw (70's) that cuts great without vibration but has two issues. Every 20th time I start the saw, it instantly trips the breaker. This happens randomly on first use one day and after repeated use the next. Changed the frayed cord, blew out the 30 years of accumulated sawdust from the switch and starter boxes and thought the issue was solved but after 2 weekends of constant use came back the third and tripped on first start. I have a new 20 amp independent circuit, 12 gauge wire (20' from breaker).

I have tracked some of the great (older) threads on this issue and noted the following options:
1. Bad Breaker
2. Bad Starter Capacitor
3. Defective magnetic starter switch
4. Centrifugal switch sticking
5. Motor winding issue

I will go through the diagnostics in the order above unless someone has a better suggestion?

The second issue is more straightforward. While the saw starts up and runs without vibration, on shutdown the arbor shutters. It appears 2 of the 3 belts are matched but one is clearly oversized. Do I remove this belt, try reordering which belt is inside, middle and outside or buy new belts?

First time poster but avid reader.