Ground Fault Detected VF0
I'm getting a 175 alarm on my 1990 VF0:
175 GROUND FAULT DETECTED - A ground fault condition was detected in the 115V AC supply. This can be caused by a short to ground in any of the servo motors, the tool change motors, the fans, or the oil pump.
I have all three axis motors physically unplugged from the control cabinet, the tool changer unplugged from the control, the fan supply unplugged from the IO board, and the oiler unplugged from the control. I still get the alarm.
Can anyone suggest any other potential causes I can look into?
If it matters, the machine is powered from a Phase Perfect digital phase converter, 230V.
If you're interested, the background :
I bought a used (1990) VF0 5-6 years ago, set it up in the shop, ran it for less than one day, and suffered a short in the x-axis cable. Turns out HAAS did a poor job manufacturing the cable and left a ball of solder in the AMP connector that somehow during transit to it's new home made it's way between the +160VDC output wire to the motor and an encoder wire coming into the MOTIF board. End result, fried the MOTIF board and the I/O board. At the time, I called HAAS in to get an estimate to fix the machine; total price with labor was going to be ~$4000 which was about half again what I paid for the machine...I deemed it not worth the cost and waited to either find parts for it myself or retrofit.
Since then, I scrounged two spare MOTIF boards from ebay (both claimed to be new) and replaced all the components on the I/O board that I assumed could go bad (namely all the ICs) and fixed the x-cable and checked all others.
I recently got to putting the MOTIF board in along with the repaired IO board. Turned the machine (for the first time in ~5 years) and voila...control booted up with no apparent issues...until it spit out a "ground fault detected" alarm.
I assumed this was due an issue in the axis motors (brush dust) so I disconnected (and disabled in the control) all of the axes as well as the tool changer, coolant pump, work light, and oiler. This didn't fix the problem. Then I systematically disconnected all outputs from the IO board and still couldn't get rid of the ground fault.
Then I got stupid and decided to override the ground fault detection, enabled the drives, and bam...immediately fried an IC and resistor on the IO board (see recent post). After some checking, I found the MOSFET in the tool changer circuit had been bad (perhaps from the original short?) so I fixed this and the IC and the resistor.
I assumed this had been causing the ground fault so I put everything back together this weekend hoping the ground fault would be solved...but it's not. With all axes and tool changer disconnected, I still get the alarm. After a full day of trying to track down where the ground fault could be coming from, I decided to override the detection again...this time no bad side effects...machine will power up and servos will enable. So what else could be causing the ground fault.
Thanks,
-Ryan
Ryan K. Dygert
www.Empire-Engineering.com