Hotbed makes ramps smoke HELP

Whenever I turn on hotbed using pronterface it causes the ramps to smoke a little. The smoke appears to be coming from just behind the hotbed output, although it is hard to tell exactly.
I am building a prusa mendel using a RAMPS 1.4 and a Arduino MEGA 2560 R3. I have checked for any short circuits or anything that is not meant to be on the board.

Any help would be appreciated. Thanks in advanced.

Quote
adamr1994
Whenever I turn on hotbed using pronterface it causes the ramps to smoke a little.

Be careful, you'll eventually run out of magic smoke.

In all seriousness though, have you check to make sure the screw connections are tight, and that there aren't any bad solder joints? Have you measured the resistance of your heated bed? Does the poly fuse get hot (the big flat yellow thing behind the power connector)?

Thanks for the reply. The resistance of the hotbed is around 1ohm. I have made sure all of the screws are tight. I turned the hot bed on at 30 degrees C but turned it off before the magic smoke because I could smell burning, the poly fuse was warm.

The smoke is coming from the MOSFET burning the header. This happened to me also. You need to get a TO220 heatsink and screw it onto the MOSFET (black thing with metal tab on its back). You also need to mount a fan above your bed and have it powered at all times. This will cool down the MOSFETs, the fuses, and your stepper drivers. If you are using a 144 watt heater (12V * 12A) then you will need to do this. Otherwise you will cook your board. Also, make sure you are using thick enough wires for both your heater --> RAMPS connection and also your RAMPS --> PSU connection. You may find those are getting really hot too if you are using wire thats too thin.

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"Never argue with stupid people, they will drag you down to their level and then beat you with experience."

I'm curious about this, where did you purchase Ramps from? Please provide the seller and price if you would like. I've ran two Ramps1.4 boards for a year now and have never had any issues with either of them so I suspect that all these issues may be related to cheap boards. Likely the all in one packages sold for ~$50 on ebay.