Hey guys! I’m working on a Road Kings at the moment and having a tough time chasing down problems with with coils locking on. I originally started off trying to fix a dead left pop bumper by replacing the driver transistor (tested bad using DVM - IJ19 disconnected) at Q69 on the board. After changing out the transistor, I’ve been running into problems with the special solenoids locking on. I should mention that there's zero corrosion or hacks on the board.
I’ve swapped out all the old SS components on the CPU board with new ones. I changed the pre-drivers, drivers (replaced with TIP102), and the 7402 at U45. I’ve also replaced all the diodes on the corresponding coils and double checked their band positions. When the game is powered on all is fine in attract mode. When a game is started, gameplay is normal for about 5-10 seconds and then a coil locks on and cooks the driver. When the game is shut off and turned back on, the coil with the cooked driver locks on immediately in attract mode. So far I’ve had the left bumper (Q69), right kicker (Q71), and top bumper (Q73) lock on all on separate occasions. Kind of stumped at this point and trying to avoid shotgun replacing anymore parts. As always, any guidance where to start troubleshooting is greatly appreciated.