From what I know of, bad MOSFETs were a problem on "fat" Xbox 360's, not the slims. The power supply turning red is a sign of a short somewhere on the motherboard. Look around for broken traces, or anything else out of the ordinary. If you want to test the MOSFETs, use a voltage meter, and place one prong on a ground point somewhere on the board (Such as the metal shielding around one of the I/O ports) and place one prong on "drain" rail of the MOSFET that you want to test. (Shown In [http://transistor-man.com/images/mosfet1.gif|This Picture], you can also use the metal tab on the end, if you wish) With the console powered on, start by testing the MOSFETs closest to the power connector on the motherboard, and work your way away from it, until you find the MOSFET that isn't working. A working MOSFET will read +/-3.3-24V on the volt meter. A dead one will show no voltage at all.