This game was brought to me for some garage workshop love. Cosmetically, it was in actually very nice condition for an all original EK, but electronically it had sat for a long time and was a complete bring back to life game.
Unfortunately, the original Ni-Cad battery was still on the bottom of the MPU and there was heavy corrosion. After getting it on the bench, I determined that this was beyond the amount of time worthwhile to repair from a cost-benefit stand point. So, I used one of my spare boards that was already unlocked and had a coin-style battery on it and dropped it in with some new EK ROMs.
On the solenoid driver board, I did my usual upgrades. Replaced capacitor C23 with a new 15,000 uf 25 volt cap, ran a jumper from the negative end of C23 to ground and tied TP1 and TP3 together. This game also had a few chips replaced and socketed on it. A lot of the joints on these were cold, as well as a good deal of the header joints. So, I reflowed all of them.
The game was also having some flickering and flaky display issues on the first and fourth player. I pulled these and reflowed the header pin joints and that cleaned up those issues on the displays.
Immediately upon boot up, the game was blowing the 20 amp GI fuse. Turns out that the ground braid was taunt and when the playfield was in game flat, the braid was shorting to one of the back GI sockets. I insulated the ground braid and dropped in a new 20 amp fast blow fuse which took care of this issue.
At this point, the game would boot but only work correctly about half the time. The other half of the time, the solenoids weren’t firing in the right order or the right solenoid. A lot of times this has correlation to pins 1-4 on J4 of the MPU and pins 3-7 on J4 of the solenoid driver board. These are the lines that communicate from the MPU to the solenoid driver which solenoids to fire. I completely repinned connector J4 on the solenoid driver with a new female connector and trifurcn .100 connectors. I repinned pins 1-4 and pin 10 of J4 on the MPU with new trifurcon .100 molex connectors.
This got the issue much more stable, but still not 100% reliable. There were still a couple solenoids not firing right. The U11 PIA is a chip component in line with the circuitry that sends the data from MPU out 1-4 on J4. I replaced U11 with a new 6821 and between that and the repinning, we were back to reliable functionality of Evel Knievel!
After getting everything off the ground and working, I replaced all the GI lamps with frosted white LEDs, replaced burnt bulbs and cleaned sockets as needed, cleaned the plastics, adjusted switches and ensured good playability and responsiveness of the game.