Thanks Rich !

Roger wilco.
Russ

Russ, you could also try deleting the driver from device manager and then running the driver test to reinstall it, just in case the driver is somehow corrupt, my vote is still hardware though.
Hood

Added to my list, thanks Hood.
You mentioned memory. Does the memory fail ? Or go bad ?
Not sure how much is there, but been fine for a long time.

Thanks,
Russ

I dont think the memory would really have an effect on the pulse frequency being wildly out but it could cause other issues and possibly corruption.
I recently had to look at a computer for a friend and it was a bad stick of memory, it had been great for 6 years but one day it just started crashing and all sorts of errors, I had a look and thought it could be memory so hauled one stick out and it was the same so hauled the other out and it has been fine since, so one stick had gone bad.

Hood

OK, thanks, I'll look into that also.

This never really crashes, just hangs up to where the mouse wont move the cursor, device mgr. wont open, totally stuck (or does that qualify as a crash). Only one way out ... kill it.
The code always runs fine. Never a hitch, except for the rpm during threading.
The PWM out must be wavering, will check that the best I can.
There are few and only slightly varying S calls in the code, so I might be able to do away with the pwm output / 106 board all together and just use the spindle relay on the 122, setting the single desired speed in the VFD itself. If the rpm stability returns, I can go that route until I get a permanent fix.

Thanks again Hood,
regards,
Russ