I bought this machine as is, not knowing what issues it had. Got it home and replaced the dead battery. I started up the machine and the MPU board lights started flickering off and on causing the monitor to also flicker off and on. So, I then did a clear ram using a key 22 chip. After clearing the ram, the machine booted up but having a “door open B” error. I checked the bill validator door wires, and they are tied together and checked continuity back to the backplane board and it was good. Thinking about the MPU board is bad. I purchased 3902 MPU board, swapped out the 3803 rev A board to a 3902 board but it also had a dead battery that I changed out. The machine booted up “Hooray” but would not accept any coins. I pressed the white test button on the comparator and displayed “Coin Jam” or something like that. I cleaned the coin comparator and coin optics. Error would not clear, so I decided to do a ram clear with key 22. Went through the clear ram process okay, put the base chip back in and I just get a white screen. I tried clearing the ram 5 or 6 times with no luck. I also tried the 3803 MPU board, it also just has a white screen. Hopefully, someone can help to get this machine to boot back up.