I like a good challenge, but my Grand Prix has just about got me whipped. I’ve been working on it off and on for six months, and it’s about 90 percent functional. That’s the good news, because when I started it was totally dead.
The bad news is it still exhibits crazy, intermittent issues. Sometimes it won’t fire the ball release coil at the beginning of a game or between balls. The top eject hole sometimes steps up the right bonus ladder more than the expected two steps. The right eject hole doesn’t always kick out the ball. The most aggravating issue is the unreliable way it steps up the ball in play. Sometimes it steps up correctly, sometimes 2 balls, sometimes not at all.
I have read all the Grand Prix and stepper related posts I could find on pinside and the old RGP newsgroup. I’ve pulled the playfield and bottom panel multiple times. I’ve examined every relay and score motor switch, only cleaning and adjusting when obviously necessary. I have disassembled and rebuilt both bonus steppers, the coin unit, and the ball count unit. I’ve poured over the schematic and feel like I have checked and tried to adjust anything that might relate to any of the odd behaviors.
Because the issues are inconsistent, I figured there was something intermittent going on, like a shorted switch or wire, or a mis-adjusted switch. But I’m at the point where I’m about ready to throw in the towel and start on another project. I hate to admit defeat – even temporarily - but I am at a loss as to what to try next. I also know Grand Prix is a complicated EM and prone to issues, but my experience with EMs tells me once they’re adjusted and set up right, they’re pretty reliable.
So I guess this is my final plea – is there anybody out there with a creative suggestion that doesn’t involve a sledgehammer? Thanks in advance for your help!