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Common Equipment Failures

Most of the time, industrial equipment is rock solid.  However over the years, I’ve noticed a tendency for certain products to have characteristic failures or problems.  Examples:

  • MEI PCI/DSP Motion Controllers and blown I/O.  The PCI/DSP is pretty expensive motion controller, and as befits its price, has opto-isolated I/O, but the general purpose I/O is not protected against over current, so anything over say 20 mA will kill the opto-isolator.  The result: blown I/O and, if you’re lucky, a $500 repair bill.  We learned pretty quickly to make sure we always had appropriate current limiting resistors.
  • AMC DX15 and DX60 CANOpen servo drives have the blinking red light.  The drive powers up, the red light starts blinking, and the drive stays mute: it will not communicate over the CAN bus (and there’s no alternate port to try).  I’ve done some troubleshooting, but haven’t made any progress.  Of all the DX15/DX60 drives I’ve bought from eBay, probably about 50% had this problem (yes, an unfair sample, since the good ones are less likely to get on to eBay.  AMC is a good company, but this record indicates that the DX has a design weakness).
  • Parker ACR9040 Motion Controllers seen to have an easily blown 24V power supply, based on eBay: I’ve seen a few advertised as “won’t power up”, and I bought one that was in “unknown condition” that won’t power up (its physical condition is fine).  I’ve spent a little time troubleshooting, but haven’t found the problem yet.  On the plus side, I’ve enjoyed taking it apart and looking at Parker’s design decisions.
  • I’ve also had bad luck with Elmo servo drives off eBay, with only 1 of 3 working.
  • I have a number of old servo drives with broken halls or broken encoders.  My guess is too much heat for the halls, and too much mechanical shock for the encoders (one even had broken glass).

Now it’s time for some screw-up stories that were totally operator error:

  • One day many years ago, as I came in the back door, I was greeted by blue fireball about 1 foot in diameter.  A tech was live troubleshooting a variable speed conveyor motor, and accidentally shorted out the motor driver, causing the fireball and the top of a driver chip to vaporize.
  • More recently, I was going to measure the current supplied by an AMC PS300 unregulated linear power supply, but had my probes setup wrong, so I shorted across the power supply.  Result: a welder!  The meter and power supply survived, but my meter probe tip melted.
  • I had a weird problem with a FP-Sigma PLC output partially failing.  The PLC’s light was coming on, but the relay driven by that output wasn’t.  The problem was that Common at the relay coil was about 2V different from the PLC’s Common, and over time that destroyed the PLC’s output.  On the other hand, I’ve shorted Panasonic PLC’s (easily if you accidentally swap the input and output cables) and they’ve always survived.



1 Dave M { 11.04.14 at 5:23 am }

Tony, I can relate to your user error story #2. About 14 years ago, I was checking the power bus on a Delta Tau 300vdc power supply. They had the test points accessible through two holes in the sheet metal cover. I accidentally shorted the multimeter probes on the cover and ended up with molten probes traveling about in the metal shelf the PS was mounted to. It left burn marks (a trail) everywhere!

2 Tony { 11.04.14 at 9:21 am }


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