I just bought a Road Kings project that will not boot. The 7 segment display shows a solid 8 at powerup. And I get the single tone. The board is very clean and shows no sign of acid damage, or history of repairs. I did confirm battery voltage at battery holder and nearby diode. Machine will respond to coin drop with audio, and can hear a very faint 'chug chug chug' if you press the start switch but nothing else. Checked voltages on power supply and I believe they all check out per online references. Nothing comes on any of the displays. Machine will not go into attract mode. (I don't think)(no lights ever flash on playfield, but if left on, sometimes plays audio) If I play with the adjustment buttons I can blindly come across audio test which all work. I almost think I have dead displays AND mpu problems, which will really suck.
New batteries installed and checked voltage with machine off, good. I did replace all caps and high voltage section of power supply and still have exact same problems. Also reseated roms and went through most connections. Press the CPU button on the mpu board and after a second or two the 7 segment display shows a distorted 3, the upper right segment of the 3 is blank.
Reading dozens of posts it sounds like an MPU problem, which is a little out of my comfort zone.
Where to next? any specifics I can check before I try and find someone to send the MPU board to? whats the going repair cost for an MPU board? Board is really clean.