3520b quitting

[Bernie Kopfer]

The lathe is 12 y/o and has only been used for hobbyist turning,I’ve never felt that the lathe had to labor on anything I’ve turned. Yesterday while prepping a 10”dia x6” honey locust greenwood blank for coring the lathe simply quit. I was pushing hard but nothing extraordinary.I unplugged the saw waited 30 sec and it started right up. A minute later it did it again - unplugged, waited and it started up and ran fine. Finished coring the piece(which IMO puts a real load on the motor) with no problems. So my question is, is this just a fluke or is something starting to breakdown? Oh and I should mention that a couple of times over the past year the machine would not start until I did the unplug- plug back in routine. And if I get a bad catch the belts usually squeal, but the motor does not shut down.

[Edward Weber]

I know others have more experience with this but this may be the VFD going bad.

[Bill Howatt]

Unfortunately, Edward may be right.
Can you see if any fault codes are displayed on the VFD when it quits?

[Bernie Kopfer]

Unfortunately, Edward may be right.
Can you see if any fault codes are displayed on the VFD when it quits?

I forgot to look. I was hoping the machine was just having a bad day, I really don’t want to see a VFD in my future!

[Richard Coers]

It can also be sawdust in the switch or just the potentiometer going bad.

[Bill Howatt]

Richard has given what are often seen as the most common problems, especially the switches. Although, if the machine starts it usually means the start switch did its thing properly and it is being (or should be) now held on by the internal circuitry.
The usual first thing to try is to blow the switches or VFD with some compressed air.

[Russell Neyman]

The usual first thing to try is to blow the switches or VFD with some compressed air.

Might need to do more. Years ago, I had a machine quit and the first thing I did was clean out the switch with compressed air. That didn't fix the problem and there weren't any other obvious loose connections, so I took the motor into the local Red's Electric and he said it was perfectly good. So, I revisited the switch and -- lo and behold -- there was a tiny spec of charred sawdust on the switch that couldn't be removed with air alone. I popped it off with a razor blade and the machine ran for another six years.

[Paul Ruud]

It sounds like the VFD to me. I just replaced the VFD on my PM3520a. They don't last forever. And the newer ones are better. There is a pretty detailed post on the AAW forums for replacing the VFD on a 3520b. Only thing is the new VFD that he used doesn't seem to be available anymore. You can get the original VFD for your lathe on eBay. But, as I said, the newer ones are better.