On Saturday 04 March 2017 11:33:27 Ben Potter wrote: > Good afternoon, > > > > I've got a converted Bridgeport Interact which decided to give up the > ghost last week. I think that one of the servo drives/amps is dead, > and am hoping that someone can sanity check my troubleshooting before > I start spending money. > > Before I removed any wires, I checked the wire numbers against the > schematic and put everything back in the same place. > > > > Fault: > > On power on, blows fuse/breaker. > > > > Diagnostic: > > 1: Remove power + HV bus from X, Y, Z drives > > Powered up, no axis movement possible > > 2: Connected power + HV bus from X drive > > Powered up, X movement OK > > 3: Connected power + HV bus from Y drive > > Powered up, X + Y movement OK > > 4: Connected power + HV bus from Z drive > > Blew fuse
>From a CET, me. Good procedure, now you know its the Z drive circuitry. > 5: Removed X drive, put Z drive in place of X > > On power up X motor ran at maximum speed until I hit e-stop Could be drive tuning. But save for future reference. > 6: Put Z drive back in place, replaced X drive. Disconnected motor > connection only from Z drive > > On power up X and Y movement OK. Good. > 7: Reconnected Z motor to Z drive > > On power up Z ran at maximum speed until I hit e-stop Different from original blew fuse symptoms. > > I'm pretty sure that the Z drive is dead - can anyone suggest any > other tests I should do? > Do you have gear to measure a Hexfet transistor? The usual transistor tester that may be part of a digital volt-ohm-meter never heard of a Hexfet, and its a different critter entirely. It sounds like one side of the h-bridge pair shorted, and its now drawn enough current thru the other side to blow the source strap inside the epoxy from the src terminal of the other side of the bridge, so its now outputting the power supply rail thru the shorted one with no fuse blowing arguments from the other Hexfet now. You will need to replace both of them. Hexfets can be hard to deal with. Bear in mind they are generally shipped with a fine wire wrapped around all 3 legs and which should only be removed by static grounded tools once the device has been soldered into the board where the bad one came out. The gate oxide can only tolerate about 20 volts before it punches thru, and you start all over again with fresh devices if that happens. And it will still be decades cheaper than a new drive from Bridgeport. If you know how to read the specs, its possible you may find even better Hexfets in a dead computer PSU, I've done it, 6 years later the controller is still working fine. > Thanks > Ben Good luck Ben. 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> ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, SlashDot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
