M4 motor runs when powered on.

[Kisssys]

Glad you got it working, we'll make note of the Fet replacement. Sometimes hot air is hard to control and using something like Chip Quik is a little easier. You need to have solder wick to get the special alloy off the board afterwards also.

[Mullet]

So I'm back bringing this one from the dead. Had another FET blow or go leaky as they say. Luckily had a replacement FET. However, Mouser says they're obsolete now. This looks like a suitable replacement...

78-SQ2310ES-T1-GE3

It looks like it has enough drain current - 6A. It's an N-channel mosfet... check. Any reason not to use it as a replacement?

[Kisssys]

Should work fine.