On 03/04/2017 12:02 PM, Gene Heskett wrote: > > 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. They are most likely either NPN or Darlington NPN transistors, not FETs. > 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 Yes, I agree. > Hexfets can be hard to deal with. Bear in mind they are generally shipped > with a fine wire wrapped around all 3 legs I have never received a transistor with wire around it. I have purchased roughly 3000 FET power transistors for Pico Systems production. The capacitance of a power transistor's gate is so huge it greatly mitigates the ESD susceptibility.
But, I'm pretty sure the servo amps in these older machines were bipolar junction transistors. However, after a fault that blew a fuse, it is quite likely the base drive circuitry may also be damaged. When I get FETs blown out, I don't even TEST the gate driver, I just replace it every time. I think at least the base drive circuits should be checked. Jon ------------------------------------------------------------------------------ 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
