107 Possibly Failing/Failed

[JrdnH]

So, the other day my spindle slowed way down, I hadn’t made any significant changes to the setup.  For the life of me I couldn’t get it working right again.  In desperation I hooked up the pot instead of the PWM and the motor worked fine.  I gave up for the night.  Came in this morning and now it’s not working at all!  Anyone have any troubleshooting tips?  Thanks!

[12strings]

Does the PMDX-107's test mode drive the spindle?

What is it's voltage on the PMDX-107's "Aref" terminal referenced to "Agnd"?  Do you have a 10V reference going IN to the PMDX-107's "Aref" terminal or are you using the 107's internal reference?

Using the PMDX-107's test mode, measure the voltage on the "Aout" pin references to "Agnd" for the two speeds.  You should see close to 10V and close to 3V (presuming you are using a 10V internal/external reference).

When controlling spindle speed from Mach, the 107's PWM LED should change brightness with commanded speed (brighter for faster speeds, dimmer for slower speeds).  Do you see that?

[JrdnH]

The 107’s test mode ceased to function day before yesterday, same time it quit controlling the spindle.  This was the day after the motor slowed down considerably.  Makes me think something was failing.  A few millivolts on the pwm out when active.   

[12strings]

When in the PMDX-107 test mode, do you see the 107's PWM LED change brightness when it is supposed to be changing speeds?  Or does it never enter test mode at all?

As per my other questions: Are you using the 107's built-in 10V reference or an external 10V (perhaps from your VFD - if you are using a VFD)?  If you are using the 107's built-in 10V, what voltage do you measure between the "Aref" and "Agnd" terminals?

Most likely the 107 is toast.  BUT, first need to verify the PWM LED is functioning and that the 10V ref is OK..

[JrdnH]

My control box was in a different orientation when I built it, now it’s very difficult to see the words on the board, but one is on constantly (assuming power) and two more come on when I enter test mode, one solid and one blinks.  I’ve tried both internal reference and using aref.  I’ll measure between aref and agnd tomorrow and get back to you.  It enters test mode, but no voltage out of aout against agnd.  I’m interfacing with the g0704 motor controller, a kbic clone I believe.  Yes, I do believe the led is dimmer when I command a slower spindle speed.  Thanks very much for taking the time to help out, I’ll measure aref after work tomorrow.

[JrdnH]

Ok, pwm led does definitely change brightness when going from full speed to 30% in test mode, status led blinks.  20 or so millivolts on aref to agnd, when in test mode or not.  20 or so millivolts on all three no matter what I do.

[JrdnH]

I really like the pmdx stuff, the 126 and 107 have been exceptional, so if I have to I’ll just buy another 107, but I’m pretty handy with a soldering iron, so if I can fix this with a few components and a little bit of work all the better!  I just don’t have the electrical expertise to diagnose issue.  That’s why I’m here, and why I’m very grateful for the prompt and informative tech support.

[12strings]

I can't give you any specifics about the circuitry on the 107 board.  If you have a strong/high powered magnifying glass you might look and see if you can spot any damaged components on the 107 (cracks in the plastic case of any of the ICs, black soot or scorch marks on the board, etc.).  Then see if you can identify what that part USED to be before it went POOF.