On Tuesday 02 August 2016 11:39:29 Rick Lair wrote: > Hello Guys, > > I have a Fanuc triple axis servo drive on one of my machines, and > since last Thursday it has been randomly tripping out, and faulting > the cnc control. It is from roughly 1995, and has been running just > fine up until this point. Even while just sitting powered up, but with > no servo motion commands it will trip out and shut off the machine. I > noticed though, that when the cabinet doors are shut, it trips almost > all the time, when I open the cabinet doors, it has been running since > Friday, only tripping just once, early yesterday morning. The cabinet > is air conditioned, and had the thermostat set at 95 degrees for the > point to turn on. We turned it down, to 75 thinking that would help, > but I think it actually made it worse. Would there be any way that on > an old PCB, if something was going south on it, a humidity level that > was too low could cause something to not work, and when it is hot and > humid, it would function properly? > > Here is a link to an identical PCB, > > http://www.fanucworld.com/media/image/800/0/A20B-1001-0770%20Front.jpg
If it walks and quacks like a duck, it probably is. I see several electrolytic capacitors of the big power type over near the heat sink. If the top of any of them has the slightest bulge or any signs of a whitish leakage around the bottom and on the board, replace them all, paying attention to the low ESR ratings, the lower the better. 21 years later we can get those caps that are better in that regard than original. While you have it apart, it might be good to remove the heat sink and clean up all the by now dried grease from both the sink and the transistors, replacing it with something like Artic Silver. Its a better heat conductor by far than what was used 21 years ago. If you find thin sheets of mica for insulators, don't lose them, put them back like you found them. It doesn't take much grease, just enough to wet and show a thin sliver squeezing out when the nounting bolts are tightened. Replacing all of the capacitors might be a good idea. After 21 years, the chance of any of the low voltage ones, rated 25 volts or less, of having their original capacitance today is not a good bet at all. If you have, or can access, a dvm that has both a capacitance scale and an ESR function, the capacitance in circuit might lie way high, but the incircuit ESR should be 100% believeable. Anything over 2 ohms on the ESR scale should be suspect. And let us know if that fixed it, please. Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Genes Web page <http://geneslinuxbox.net:6309/gene> ------------------------------------------------------------------------------ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
