mosfet problem

[eggman]

hi everyone i am new to this forum and i need a small bit of advice regarding some mosfets i have fitted to a 30A dc motor controller - the problem i had was a small bit of metal fell in to the control unit i had open whilst testing which resulted in the magic smoke escaping form the 2 x NCE7580 mosfets (at this point i think the pwm side of the board was still working) i had 4 x RFP50N06 mosfets laying about so thought i would attach them to a large heat sink and wire them back to the board - now it doesnt work and i dont have the electronic know how to find the fault (my thinking on the matter is 1. its the wrong mosfets altogether or 2. you cant use 4 in place of 2???

any help on this matter would be most helpfull and rewarding to me due to my small understanding of components - but i am trying!!!

when i stick the fluke on the mosfets i get nothing on the gate (pin 1 ) and nothing on the middle pin (output?) and negitive on the input? its a switched negitive

thanks again in advance

mike

[Thomas W]

An RFP50N06 is able to switch 50 A, and you mentioned 30 A for the motor. With sufficient cooling the RFP50N06 should be able to do the job.
What kind of controller is it? (Brand / model / DIY) Do you have a schematic?

NCE7580: http://www.dzsc.com/uploadfile/company/ ... 837365.pdf
RFP50N06: http://www.fairchildsemi.com/ds/RF/RFP50N06.pdf