Inverter problems on my Powermatic 4224

[Jim Kilton]

On and off. While turning on my PM4224 the lathe will just quit running. I have to disconnect the power and the lathe will restart.this happens frequently and sometimes not at all.
I have changed my switches and checked all my wiring connection in my inverter.
any suggestions what to look for. My lathe is an early 4224 about 15 or 20 years ol.
jim kilton

[Richard Coers]

Have you checked all the way back to the breaker box? Checked line voltage to the lathe? Potentiometer is the biggest problem, any signs of trouble increasing or decreasing speeds in the past?

[Dick Strauss]

Sawdust getting into the red mushroom switch is the most common problem that I'm aware of currently. Eventually it gets so packed full that it limits the front to back travel and the actual switch mechanism on the back does not activate.

[John K Jordan]

On and off. While turning on my PM4224 the lathe will just quit running. I have to disconnect the power and the lathe will restart.this happens frequently and sometimes not at all.
I have changed my switches and checked all my wiring connection in my inverter.
any suggestions what to look for. My lathe is an early 4224 about 15 or 20 years ol.
jim kilton

The same thing happened to one of my jet 1642 lathes, identical symptoms - some times it worked after unplugging for a at least 15 seconds and sometimes it didn’t except after several tries. I used it for several years like that until one day the inverter failed completely and never came on again. (The LED display on the back stayed dark) I tried disassembling and debugging the internal circuits but was unsuccessful without a circuit diagram or a second one to compare - besides, due to the construction it was difficult to get to some of the internals. I gave up and replaced the inverter with an inexpensive one.

I read that sometimes an electrolytic capacitor on the internal bank will go bad but that didn’t seem a problem on mine. The on/off switch and the speed/reverse controls are on a low voltage circuit and easy to test.

There are places that will repair these inverters but I don’t have a contact.

[Jim Kilton]

I mostly use my remote switch and seldom the red mushroom switch.
I have replaced the remote switch and it does the same thing. May go for days or hours or minutes befor shutting down. As I said after disconnecting power for a few seconds it usually comes on and my work the rest of the day.one other thing my display lights never go dark.

[John K Jordan]

...one other thing my display lights never go dark.

What does the LED display on the back show, both when running properly and when the lathe doesn't come on?

If it's one of the Delta inverters it should have a F (for frequency) followed by a number (0.0 when not spinning, higher otherwise). Does it give an error message those times when it doesn't come on?

This is mine from a PM 3520B, powered on but not spinning.

484803

JKJ

[Dick Strauss]

The remote switch gets sawdust in it as well. Trace the wires and test the switch for continuity the next time you have the issue.

[John K Jordan]

The remote switch gets sawdust in it as well. Trace the wires and test the switch for continuity the next time you have the issue.

I don’t know of this particular problem is caused by a malfunctioning switch (or two) but switches are trivial to debug - either disconnect and check continuity or disconnect and simply short across the correct terminals on the VFD with a wire and see if the lathe starts. (the control circuit and switches use low voltage - no danger of dying unless one does not understand which terminals are which) I’d jumper first at the screw terminals inside the inverter then if that worked continue to the wiring and switches.

If the big mushroom switches are in fact not functioning I remove and disassemble them (don’t loose the tiny detent ball), clean as needed, polish the contacts with 1000 grit paper for good measure, apply a thin film of dielectric grease on the contacts, reassemble and test. If working and the problem was due to dust I seal the outside with silicone caulk, wrap well with plastic wrap, then reinstall and test again. This has permanently restored switches on several lathes and other equipment.

Note that if the potentiometer or connection is bad the lathe might not run even if both switches are fine. All these have to work together. If the VFD is ok someone with experience and the manual could prob debug the control circuit in a few minutes. If more than one thing is wrong at once it might be a little more challenging.

The report that the display on VFD is not dead is a good sign. It concerns me though that the symptoms described (working after unplugging and replugging) were similar to one of my Delta VFDs that eventually died.

If he hasn’t done so the OP might read Doc Green’s article on Powermatic lathe control circuit debugging. The lathe model is different but the principles are the same.