I have a Stern mpu100 thats not flashing LED. When I power up the game the LED is stuck on, first thing I did was pull all the chips off the board and I tested them in a working game and they are all good. Irie socketed you ate also replace some transistors and diodes but still no luck. the board is super clean with no corrosion on it believe it or not. I went over every solder joint ,check continuity on everything seems to be good but still can't get the board to flash. Reading a lot of stuff online but it's mainly confusing. The proms that are in the board are for the game originally was working with no problems so it's not a jumper. All tests Point show proper voltage. Don't know where else to go from here.