MOSFET burnt out

Please could someone tell me why the mofset next to the power terminals has burnt out. Unfortunately I don't have a multimeter to hand so does anyone know a way I can make sure this doesn't happen again as I've just ordered a new ramps board since my old one got quite damaged.
Thanks for the help.
Ben

The MOSFET can be damaged by short-circuiting the + and - on the output terminals, or grounding the metal tab that sticks up from the chip. It can also fail due to too much voltage or too much current, though the polyfuses should protect against over-current. Don't throw away your old RAMPS board - the MOSFETs are very inexpensive and easy to replace...

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-David

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Don't buy crap ramps board with cheap MOSFETs from china....

Infact replace the MOSFET on D8 imediatly no matter where you got the ramps from, as the standard MOSFET is not good enough for the job, it needs a heat sink and a fan on it.

Use any of the MOSFET replacments in the list below.

Best mosfets for driving your heated bed: IRLB3813, IRLB8743, FDP8870, AOT240L, CSD18502KCS. These mosfets will run merely warm with NO heatsink and a load current of 10A. They should be good to over 15A with no heatsink according to the worst-case numbers in their datasheets and is also [reprap.org]

Edited 2 time(s). Last edit at 01/21/2015 02:52AM by Dust.