Author Topic: Incorrect voltage on PMDX-107 VSD interface  (Read 1764 times)

jrbloom

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Incorrect voltage on PMDX-107 VSD interface
« on: April 19, 2021, 12:51:12 PM »
Hi

I am just bringing up my new CNC controller electronics, using the PMDX-126 and PMDX-107 boards. PMDX-126 seems to be behaving correctly and motion/sensors doing what I would expect.
However my Spindle operates at only around 60% commanded speed, and the VFD also reports similar commanded frequency.

Mach4 logging shows that it thinks the PWM is at full duty cycle (max speed). Voltage on the PMDX-126 Port1/Pin16 is also around 4V confirming the PWM is near full duty cycle.

I measured the voltage across Aout/Aref and sure enough I only see ~5-6V. As a sanity test I flipped the 10v/5v switch and Aout falls to ~3V.

As a final verification, I checked behaviour with the PMDX-107 test button. This shows exactly the same behaviour.

A secondary observation is that sometimes the PMDX-107 stops commanding completely. I see the Port1/Pin14 and 16 LED's flashing as expected on the PMDX-126, but the PMDX-107 LED's remain off, except status. Hitting RESET on MACH4 (not sure what this does yet, this is my first CNC) usually brings this back.

Is my 107 board duff?

Thanks,

Jon

Steve Stallings

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Re: Incorrect voltage on PMDX-107 VSD interface
« Reply #1 on: April 19, 2021, 03:38:32 PM »
Jon,

We have identified an incorrect resistor value that was installed in the output protection for the Aout signal on a couple of units and based on serial number yours is likely one of those. The output voltage would check out correctly using a high impedance meter during testing, but would droop under the lower impedance load of the VFD input.

Please return your unit for free warranty repair.

Our shipping address can be found here:

http://www.pmdx.com/ContactUs

Sorry for the inconvenience.

Steve Stallings
PMDX
Steve Stallings
www.PMDX.com

jrbloom

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Re: Incorrect voltage on PMDX-107 VSD interface
« Reply #2 on: April 30, 2021, 12:21:27 PM »
New board installed and working fine, so this was the issue. Thanks Steve.