11 Insights into EM Pinball Machines

After many years being a bit of a pinball nerd (never to the point of owning one, and not playing regularly for many years), here are 11 surprising, interesting, or amusing things I've enjoyed learning about or messing with on my new (recently acquired, far from new) pinball machine.

#1 - There's an On/Off Switch. Who knew? Not I, who was using the power cord (switched via a plug strip) for the first week or two that I owned the game. When I received the schematic, the switch was on there, and I went and found it (a push-button, under the table on the right front side). It does not really look like a switch from the top - a black, round cylinder that I assumed was a tilt mechanism or something. 

The inscrutable, stealthy On/Off Switch (left) and as a bonus, the "Knocker" which slaps the side of the cabinet when you win a free game

#2: The tilt mechanism. Really a fascinating bit of electro-mechanical tech, with a weighted pendulum suspended in a conductive ring. If it moves enough so that the conductive wire supporting the pendulum hits the ring - you tilt. And you can adjust the sensitivity by raising / lowering the pendulum.

For a few moments I thought the "anti-cheat sensor" was a spare ball or place to store the ball when removed from the game. It's there to prevent someone from lifting up the front of the game to move the ball around.

#3: The other tilt mechanism(s). This particular game also has several bounce switches and an anti-cheat switch. And I think there's a "Slam Switch" in the door to prevent folks from jarring the coin-up enough to register games.

Tilt / Bounce switch. There are several of these sprinkled throughout the cabinet / back-box in different orientations, they activate in response to sharp blows.

The various tilt mechanisms do different things - some end the ball (mild), some end the game (more serious), and some cut power to the machine and you need to power down to reset. A surprising number of ways to discourage table abuse!

#4: There's Only One Ball. I guess my experience with home / toy pinball games was that there was a reservoir of balls (3 or 5). But nope, just one. And it's considered good practice to replace it from time to time to preserve the wooden game surface. I bought a new ball for my game, right off the bat.

I had this battery powered Marx Oasis pinball game as a kid, which had five balls lined up. I guess I assumed all pinball machines worked that way.

#5: Three Ball vs. Five Ball. On this machine (anyway) there is a way to program the number of balls per game (also the number of games per quarter), using rather crude (at least from my engineering experience) "Jones Plugs". I've perhaps noticed the "number of balls" per game evolve over the years, but did not realize that games could be set up either/or, nor have ever noticed that a particular game was set for 3 balls in one place and 5 balls in another.

I've got mine set up for 3 balls - it's a pretty simple game to score on (just this morning, screwing around, I won 3 games on points in a single game), when I'm troubleshooting I'd just as soon not have to run through all five balls, and when playing friends, 3 balls is a nice contained game. 

Move the little plug strip to the left for 3-ball or the right for 5-ball. The rules and bonuses change slightly depending on number of balls.

#6: Adjustable Bonus Awards. One of the first things I discovered / played with. To set the levels for free games, you insert a pin (representing 10,000s) into a receptacle (representing 1,000s). So for 43,000, you put the 40,000 pin into the 3,000 receptacle. 10 pins, 10 receptacles, which kind of forces odd-ball award numbers.

I was tickled by the process / tech and also by the holes drilled into the plywood panel to store the unused pins. And, also an interesting surprise, there is a website out there which collects and makes available (for free) very well done reproductions of the game instructions and award levels.

Another thing I probably intuited over the years without actually understanding the tech - I'd notice that certain games were easier to win on than others, see these ubiquitous replay award cards on every machine (that all seemed to look alike) but never really understood that it was all set up by the manufacturer. In fact, the download of the instructions and award levels cards includes a table of suggested award levels (liberal to conservative) with recommended baseline levels for 3-ball and 5-ball play. I'm working with the 3-ball recommended levels.

#7: Jones Plugs and Removable Heads. Speaking of Jones Plugs, the back-box of head of the pinball machine can be removed for transport / service, with the electronics disconnected using banks of these Jones plugs. Good place for bad connections, I'm guessing.

#8: The Scoring Motor. Kind of the beating heart of the these old EM (electro-mechanical games), it's kind of like a pulse generator, using a rotary device (motor), multiple cams, and multiple N/O and N/C switches to provide pulsing signals. Here it is in action (start-up).

#9: The Chimes. Also inside the box is a set of three chimes (effectively xylophone bars) with coils and free floating plungers inside - one for 10s, one for 100s, one for 1000s. So if you hit a 100 point target, the chime rings once - DING. If you hit a 500 point target you get five quick strikes - DING DING DING DING DING. And if you turn-over from 900 to 1000 (for instance) you get two chimes in pleasant harmony. A lot of the warm-fuzzies of the pinball machine for me are wrapped up in lights, sounds, and the physicality of the game (flippers, pop bumpers, clicks and clacks and thumps)

Mine are working pretty well (video at the bottom of this post), but that did not stop me from ordering a chime tune-up kit, including new rubber grommets and washers for the chime bars, sleeves for the plungers, and rubber padding for the top and underneath the plungers.

#10: Stepper Units. A lot of the logic / memory in the pinball game are recorded in rotary devices called Steppers. There are the scoring reels (I have 4 reels per player, 8 reels total) which keeps track of and displays the score, sends a carry digit signal (transitioning from 9 to 10) and provides output for the game in terms of zero (to reset), the 10s digit (for the end of game "match" function) and the 10,000s and 1,000s digits (for the high score award).

Stepper unit that tracks the player number (in my case, 1 or 2, although it's designed for up to 4) as well as the ball number (1 -3 or 1 - 5). This is in the back box, there is a similar unit under the table that tracks the bonus points accrued.

Credit Reel, which keeps track of number of games (mechanical reel visible on backglass). Mine goes up to 15; there are relays to track when it's at maximum and when it's fully decremented (no credits)

Scoring reel. This is the 100s reel (no circuit board output), the 10s reel has a board for the match function, the 1000s and 10000s reel has a board for the high score / free game award function

#11: The Backglass. Kind of the aesthetic focus of the game. A simple glass plate with artwork painted on it from behind. Mostly opaque, but some clear spaces (for scoring reels / credit reel), and some transparent (for indicators like Game Over, Tilt, Player Number, Ball Number, as well as a few cosmetic spots. My backglass is in pretty good shape; a few spots burned through (by way of hot incandescent lamps). I covered a few burn spots (black areas above the score reels) with tape; I replaced most of the hidden lamps with frosted, warm white LEDs (behind the glass and under the table). there are a few painted spots that could use a touch up if I get around to it; nothing critical.

Right now the Game Over lamp remains incandescent (a special blinking bulb, like those old xmas lights). Apparently, the original design of the game featured blinking lights behind the robot eyes and I might buy some of those.

And oh, even though the backglass is pretty important the table surface itself is the real star of the game, and mine is in great shape - looks original, with no touch-ups and very few scuffs or worn areas. I bought some wax to keep it that way.