I Can't Get A Break

[gmay3]

Sorry to hear it Zulfe, don't be discouraged by these few issues you're having, stuff like this can just happens when you build your own 3d printer! You'll get it working!

Personally, I've tinned my wires that go into each screw terminal because in my experience, connections pull out more easily and are weaker when left stranded. Regardless, whether they are tinned or not, I don't think this alone is the root of your issue. It is more important to make sure that all of your wire slack is anchored to the frame so the wires aren't pivoting at the board connection when the printer moves. Your issue is that that one wire touched another while both were in the connector either by loosening slightly after being pulled on by the printer or by having too much wire exposed between the connection and the insulation during the installation. This also makes me want to go back and check that my screw down terminals are still tight!

Before buying a new board, does it still provide all other functions except the heat bed? If so, could you remove the burned connector and solder the heat bed wires directly to the board? To test this I would power down your printer first and remove the heat bed connector. Once it's cleaned up command the heat bed on with prontorface and measure the voltage between the two pins on the board where the connector used to be, also being careful not to touch the multimeter leads together. If everything's working the best practice would be to order a new screw down connector to replace the burned one. If you need help finding a replacement I'm sure we could help you look.

UPDATE BEGIN
I recently redid all the wiring and wire routing on my printer and after testing the strength of tinned wires and untinned wire terminations in the screw terminal, I 100% agree with printbus and Mjolinor that the wires in a screw terminal should NOT be tinned. Especially if you are trying to fit more than one wire into the terminal. Make sure that you twist the ends of your stranded wire before inserting the untinned end into the screw terminal. Many thanks to printbus and Mjolinor for educating me!
UPDATE END