Old Engineers are Amazing

I just spent the last 40 minutes up to my elbows with a fellow student in the nether regions of a pinball machine. It's an old Adams Family pinball table that the student hangout and pizza joint recently acquired and it wasn't working; the ball would vanish down a little chute and should have been knocked to the side and then shot out. When the solenoid triggered to knock it to the side, though, the ball didn't move. We pulled the ball out to look at the chute and I found a light bulb from elsewhere in the machine had been knocked off and gotten stuck in the chute, preventing the ball from going through the hole in the side. We pulled it out and the machine worked.

Mostly. The screen didn't, which is kind of a pain. It appeared that everything else worked, so after some rooting around we discovered a key hanging inside the case of the machine that, once we tested it, opened the panel that the screen is on. We took it out and looked around to find a very smoky looking fuse -- we suspect it was blown when Ross zapped himself under the table, but we couldn't quite tell and didn't have a spare on us. We'll go back soon and check to see if that was it.

But the cleverness that you see in old mechanical things! It's really amazing what those old-timey engineers could come up with. Take the bumpers, for instance. They are a plastic or metal tube that the ball collides into. Around the base is a pressure switch that the ball presses when it hits the bumper. That switch triggers a solenoid (almost everything in the machine is a solenoid) that drops a metal ring from the top of the bumper. The ring is concentric with tube part of the bumper but slightly larger around so that it hits the ball somewhere on the bumper-side of the ball's center, forcing the ball away from the bumper. There was also a solenoid pointed at the side of the case. The best guess that Ross and I could come up with was that it was for making big thumps as sound effects.

~KMarsh