We had our first adventure in pinball-machine repair. One of the drop targets on our Tri-Zone --- the Z --- was sticky. A good solid ball hit would make it drop, but it took a more solid hit than the O, N, and E targets did. MWS, who sold us the machine, described what needed to be done to fix that. There's a circuit board behind it, and the drop target registers a hit, and drops, and scores, when two contacts on the board get jostled by the ball hitting the target. If the board's a little out of place, the drop target gets sticky. So to fix it, we'd open the machine and lift up the playfield --- there's a built-in metal brace to hold the playfield up, exactly the way a car's hood has a metal brace --- and fiddle with some screws to get the sensitivity right. We did poorly at first until MWS explained the drop target had to be dropped for the relevant screws to even be visible.
Also, bunny_hugger had studied the problem with the bonus lanes. There's two channels near the top of the playfield, labelled A and B, and the ball has to roll down both to increase the bonus multiplier. But it didn't always register when it rolled down B. She noticed that on either side of the A lane were plastic walls, guiding the ball over the switch (a bent wire) that makes contact to register the rolling. There was a missing plastic wall for the B lane, though, and she thought the extra space a ball had might be why it sometimes missed the B lane.
She found on Marco's --- a major pinball-parts supplier --- lane guides for that era of pinball machine. And she installed it. It's nearly a perfect match for the lane guides that were already on the machine. It's brighter, but that's probably just a matter of the plastic not having faded. And the B lane now registers perfectly; we haven't caught it missing yet.
And then we opened up one of the bumpers and tightened up the light inside. It's now lighting reliably. We also put the cap back on correctly; it had gotten rotated 180 degrees sometime in the past, so that the design on it was out of step with the design on the two other bumpers.
So this is our first experience with doing actual, if minor, repairs on a pinball machine. bunny_hugger also bought a bag of all the rubber pieces in the machine. When we feel up to the challenge of cleaning it properly we'll also try replacing all the worn or ready-to-crack rubber bands.
Trivia: Fox, Henderson, and Company's contract for the Crystal Palace for the Great Exhibition of 1851 gave a price of £79,800 to build, and later dismantle, the building. (It would end up costing more than £200,000.) Source: To Engineer Is Human: The Role of Failure in Successful Design, Henry Petroski.
Currently Reading: 1946: The Making Of The Modern World, Victor Sebestyen.
PS: Reading the Comics, December 23, 2015: Richard Thompson Christmas Trees Edition, returning to the world of comic strips and trees.