gecko problem ( I think they are trying to kill me )

[Senor J]

I have my gecko 320 servos hooked up to my power supply 80v They were acting very flaky with step loss and such. and so I did some poking around and found out that the heat sink that they are attached to is hot, as in carrying voltage, and lots of it, enough to where when I touch the heat sink with a ground wire it sparks( not just a little, the sort of spark that is trying to kill you.) There is no power source touching the heat sink other than the gecko drives. When I lift the geckos off the heat sink it is no longer carry a charge( I can touch a ground wire to it and no sparks) So the gecko drives are acting like a positive terminal applied to the heat sink. Anyone had this problem and know whats going on?

[Larken]

Put insulators under the mosfets (mica or other).
Sounds like one of the high side ones is touching the case.