A short circuit on your board. It can be caused by liquid or solid bridging two circuits with power running through them. It is like a welder and creates heat. Improper soldering can create this situation too. Sometimes it's caused by improper hookup but this is rare because the wires dont just hook up anywhere you want them too. Too much power going through transistors and resistors and circuits will burn it too.(this is usually due to a faulty power source or if your switch it set to the improper voltage)
Linear Mode
