I got this cabinet originally from Gaymond Lee, a great dealer in Southern California. It was complete except the power supply was missing, so Gaymond gave me a good deal on it. The control panel stickers were also gone and the special "Hall Effect" joystick was very stiff and "sticky".
I never found a replacement power supply for it, and I hear the originals aren't too reliable anyway, so I put a switching supply in and an audio amp since the original amp came on the power supply. The monitor AC power wasn't connected to the isolation transformer, so I wired that up. Unfortunately, I got the wiring wrong and I blew up all kinds of stuff on the monitor chassis. Clay Cowgill was kind enough to sell me a new chassis, so after figuring out my wiring mistake, that got the game working. There was, however, weird sparkly white dots all over the screen. The advice from the experts was to replace the video RAM. I desoldered it all and added sockets and a new set of RAM. This cleared up all but one tiny white dot, which didn't bug me much, so I left it. Yay, it was playable! I brought the game to the first CA Extreme show, where it lasted through the first day but on the second day when I turned it on, the screen would rapidly flash solid white like it was a light-gun game with the gun on full auto. I pulled all the video RAM, searched the various pinout databases and found I could use 41256's without modification. These should make for a more reliable, plug-and-play replacement. That cleared up all the video problems, including the little white dot left over from my previous fix. The game played fine for a few months after that, then the polygons started freaking out. The experts advised that I replace the math box ROMs, so I did. Problem fixed again. About a week later, the monitor blew it's main fuse. I replaced the fuse and it just blew again. Ugh. Probably a shorted HOT, I'm told. Since I had no idea where the HOT was (horizontal output transistor) and it's not labeled "I am the HOT" on the schematics, I pulled the monitor (a "Disco") and replaced it with a nice faithful Well-Gardner. The last remaining issues were the missing control panel stickers and the stiff Hall Effect stick. Clay came through again with scans of the stickers which I redrew and printed on sticker paper. They look pretty good installed! Then I found someone selling a NOS, never used Atari Road Runner control panel, complete with brand new Hall Effect stick. I bought it and put the stick on the I, Robot and now it plays like a dream! What a big difference the joystick makes! I really love this game.