If the thermal pad blob on the back of the board was touching the case, that'll cause a drain to ground short, which would be the same as a shorted MOSFET. Still measuring a short with the board pulled?
But if the MOSFET is dead anyway, specs are gonna be...
Package that matches whatever's on the board (though you could ghetto rig a TO-220 on there if you wanted to)
Vds rating of 40V or better
Logic level (5V) compatible gate
Rds(on) of 20mohm or better at Vgs=5V - this way the FET dissipates 1/2 watt at 5 amps, so it shouldn't burn up even if they totally fucked up the heatsinking.
If there aren't any clamping diodes across the terminal blocks for the heaters/fan, grab a few shottky diodes too. 1A/40V (like MBR140 or MBRA140 or whatever) should work fine. Put them across the output, cathode to +24V, anode to output.
But if the MOSFET is dead anyway, specs are gonna be...
Package that matches whatever's on the board (though you could ghetto rig a TO-220 on there if you wanted to)
Vds rating of 40V or better
Logic level (5V) compatible gate
Rds(on) of 20mohm or better at Vgs=5V - this way the FET dissipates 1/2 watt at 5 amps, so it shouldn't burn up even if they totally fucked up the heatsinking.
If there aren't any clamping diodes across the terminal blocks for the heaters/fan, grab a few shottky diodes too. 1A/40V (like MBR140 or MBRA140 or whatever) should work fine. Put them across the output, cathode to +24V, anode to output.