Burnt Mark On Circuit Board
There will always be a decision whether to scrap off the burnt mark or just let it remain at that way. Please see the photo. It all depends on the problem. If the problem is intermittent then it is advisable to remove/isolate the burnt mark. Even if it did not pose any problem at current moment it doesn't mean that the circuit will be stable in the future. This means it has the possibility to cause problem after many hours of using the equipment. The reason why the particular circuit board became darkened was because of a resistor placed too near to the board. The resistor was tested good. The best solution is to place the resistor with longer lead so that the resistor body would not touch on the circuit board. And at the same time scrap the darkened area off with a blade to prevent any conduction between circuit tracks or components. This will eliminate future solid or intermittent problem.