I have been chasing a reset/lockup problem with my road kings for a while now. Played about a dozen games today trying to pinpoint exactly when and what it does.
Here are some symptoms when I have my problem:

-While entering initials for high score, the displays went crazy and the 7 segment led on the mpu said the number 7, and locked up
-Locks up, music still running, playfield controlled lights go out, display is garbled, 7 segment says 0
-Locks up, no music, playfield controlled light stay in last state, backwards F on 7 segment display
-Locks up, All displays dead, playfield lights go out, 8 on 7 segment display
-Game resets after a minute of play after hitting left flipper, just like game over, can start a new game no problem, no error or lockup
-Game locks up after a minute or 2 of gameplay, Left and right rear controlled gates buzz, appears to be left flipper related
-Game locks up after right flipper hit, playfield lights in last state, displays froze at last score, flippers still work, slingshots still respond, Pops still respond, most other switches do not respond.
-sometimes after a reset and turning the game back on, the high scores will have garbage characters, a factory reset fixes it.

Shutting off the game and powering back up restores it back to normal. I often can not complete one 3 ball game.

I rebuilt the power supply, same thing, Bought a new 'gulf pinball' power supply, same thing.
Made sure all my ground braids, and screws for the boards are tight.
New big blue capacitor.
made sure ground pin is on wall cord.
Because it seemed very often related to the flippers, I replaced the flipper control board, EOS switches, new flipper cabinet switches, new flipper coils, new diodes on flipper coils.

I DID find that the heat shrink on the flipper pawl was worn out, Replaced that too...but maybe the damage is done.

What in the world can I do next?

Thanks!
~mope

Sunday morning bump

I will check on the C30, as I have read similar. The board is clean and never had any battery damage.

I do have another symptom/update.

While playing again it 'sort of' locked up. The displays showed some garbage, but the game would still play and score. I continued playing for like 30 seconds, Shot the ball in the 'left eject hole', coil was not strong enough to kick it out, it fired maybe 20 times before I shut the machine down. The coil was hot and smelly (20 times didn't seem like long enough to melt it) But when I took it apart the coil sleeve did have a stiff spot and would not allow the plunger to move full stroke.

The ball eject to the shooter lane has been a little weak lately too...I have new coils and sleeves ordered, I will check back.

A weekend update.

I replaced the outhole coil and diode. Played like 5 games fine. Then game locked up again. Turned the game back on and it would not start a game and would have lay a sound sample over and over again. Started looking into it and found none of the solenoids worked, found the solenoid fuse blown. Changed the fuse, and the looping sound sample stopped, and I can now play a game or two until it decides to lock up.

Through about a total of 15 games I had my good fluke meter on the 5v and it was solid 5.04 the whole time, even during lockup.

I also replaced the c30 with a new cap, no change.

What else can I check?