Hello.
I have been using DM860A drivers from Longs for awhile on my CNC augmented Smithy 3-in-1.
When I wanted to machine manually I switched the drivers off and turned the handles slowly to keep EMF backfeed under control.
This week I wired up the Enable lines and it was great. The motors de-coupled, turned freely, and all was well in Grouchyland - for a day.

I'd be working a part, stop a bit to answer the phone or something, and come back to a fried driver or power supply. The drivers were powered up but the machine was idle. I thought it was a fluke, maybe a loose motor wire, or a Voodoo curse placed upon me by the wife. I repaired the driver and moved on. Yesterday it happened twice! Two drivers and a power supply were shorted out. I fixed the drivers but now have to wait for power supply parts. The only change to my system is the use of the Enable lines.

These drivers are Enabled by default and disabled by changing the EN state. When disabled, the drivers seem to decouple the motors rather than ignore pulses. The motors can be turned without EMF feedback or cogging

The drivers are powered by 60V / 350W switching supplies - one per driver.
Drivers use two MOSFETs and one 2a/400v snubber diode per motor line.
The drivers run bi-polar 4-wire NEMA 23 and 34 motors and the current is set accordingly for each.
Destruction is random and happens whether an axis was used, even manually, or not.
Damage has been somewhat consistent - a shorted MOSFET and diode on a random motor line.
Power supply damage ranges from protection circuit shutdown to blown 8A fuses to fried 15A switching outputs. Oddly enough, the dinky fuse in the driver never blows - go figure.
Driver pulse and enable lines are configured HIGH (common +5vdc / pulsed or switched low).
The Enable line was toggled using an SPST switch.

I checked the EN + and - pins with a meter for voltage and resistance to the case and the +5/GND rails looking for loops or backfeed issues and got nothing. The pins appear isolated to everything.

I need to know if it's me and how I use the EN function or how I have it wired OR is it a poor design in the driver.
I assumed the motors were electronically decoupled gracefully and wouldn't damage the drivers but it appears to act just like yanking off the motor leads.

Should I be able to spin the motors freely while disabled?
Would common anode vs cathode wiring make any difference? I don't want to risk any more of my rapidly diminishing supply of spare parts to experiment. I don't know if these are re-badged Leadshine drivers or cheap copies so I can't really ask them for help.

Lastly, is there another method to electrically decouple the motors without frying anything?

Thanks,
Ed

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