I saw the picture of the resistor added. This was never done by factory as they would not put burned heat shrink if it is heat shrink- it might just be some plastic tubing. Idiots get into these all the time and it is easy to see if a bonehead has worked on them. I come across units where boneheads do marginal work all the time. Usually if they made adjustments to design it is small resistors that are glued to the board and sometimes have a fiberglass sheet under them. I have never seen a low wattage resistor like that ever put on that board and if I did it would get changed out for an appropriate 3 W flameproof resistor. There are a lot of people that think they know what they are doing but then you discover this which tells you the real story.