The step-by-step logic of old pinball machines

The step-by-step logic of old pinball machines

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When you need a machine to count but you don’t have a computer, just build yourself one of these. This is a stepper unit - one of six inside this pinball machine. In a previous video, we looked at the targets on its playfield, how the machine totals and shows you your score, and how, with a few relays and a wacky contraption called the score motor, the machine can perform automated sequences. Sequences such as awarding 5,000 points with a single switch hit, or even scanning through the five letter targets and awarding points based on how many you hit earlier in the game.

If you haven’t seen that video, I would highly recommend watching it first. I've summoned a clicky thing for your convenience. A lot of what I cover here builds from that video, and since we’ve got a lot ahead of us still, I promise you that I will be striving with fervent commitment to restrain my various recapitulations to as diminutive a quantity and length as I can possibly muster in the (perhaps optimistic) hope that my restraint in this matter will result in a more economical expenditure of that most precious and finiteresource we call time. We’ll begin at the start.

Pinball machines are an awful lot of fun, but we mustn't forget that the primary reason for their existence isn’t fun — it’s money money money! This machine’s prime directive is to relocate some quarters from your pockets to the cash box locked inside. And to make that more likely, it doesn’t work unless you put money in it. When the “game over” indicator on the backglass is illuminated the flippers are disabled, the ball gets a break and chills in the outhole, and the only way to start the game and play it is by feeding it a quarter. And would you believe it’s literally the quarter that starts the game? ‘Cause it is.

This leaf switch here is what will kick the machine out of game-over mode and start the reset sequence. And it’s actuated by the movement of a small trip wire that quarters fall onto if they’re accepted by the coin mechanism. Coins that are rejected by the coin mech will fall forward of this point and end up behind the coin return flap so you can get them back.

Now, I’m not gonna get into the actual coin mechanisms here. But I will add two bits of trivia. Oh, right. Firstly, these coin mechs are modular components that can be swapped without tools.

Partly that’s for maintenance considerations - these are fiddly things which need occasional cleaning, adjustment, and possibly replacement. But they can also be swapped for different denominations, and when this particular machine left the factory, one of these coin mechanisms probably accepted dimes. You’d get one play for 10 cents, or three plays for a quarter - a volume discount! There are several options actually as far as how you want to configure the plays per coin type, and this coin door can even accommodate a third coin mech in the middle position - right now it’s simply blanked off.

At some point in this machine’s life, its operator swapped the dime acceptor for a second quarter acceptor, changed the faceplate to reflect that, and configured the machine for one coin one play. The other interesting thing here is this: the coin lockout magnet. This electromagnet must be energized in order for the machine to take your coins. If it’s not, spring tension causes small wire loops to poke into the validation path of the coin mechanisms which causes them to return all coins even if they’re deemed good. The purpose of this is twofold: one, if the machine is switched off it can’t possibly start a game, so you don’t want it taking people’s money.

And secondly, even when the machine is on, it can only process one thing at a time. If, say, you wanted to add a second player (which you do by feeding it a second quarter) but you did that while it was in the middle of the reset sequence, the coin hitting the leaf switch wouldn’t actually do anything, thus the machine would just steal your quarter, and you’d be mad. To reduce the risk of that happening, the coin lockout magnet gets its power through a switch on the index stack in the score motor. It will thus only be energized when the score motor is stopped and idle, which is the machine’s only state in which it can correctly process that you’ve inserted a coin. Technically someone could shove a quarter in at just the right moment and still have it get eaten, but the odds are very slim. [clacking as magnet energizes and de-energizes] Moving on, though, between games the machine stands by in game-over mode where nothing works and this light is on.

And what puts it in game over mode, you ask? Why, the game over relay! Which lives here in the main cabinet. This is effectively the main on/off switch for the game’s automated functions. This switch within the relay breaks the return path to the transformer for an awful lot of stuff including the flippers, the bumpers, all of the targets and their respective relays, basically the whole game stops working when the game over relay is tripped. Because, ya know, game over.

Now, you may notice that this relay is not like any of the others we’ve seen. It has two electromagnets because this is a latching relay. Not, it should be noted, a relay which “latches” by powering itself through some other switch somewhere else in the machine, but one that mechanically latches into one of two stable states. This coil, the trip coil, will shut off the game once it's fired.

The other coil is the latch coil which… turns on the game once it's fired. Also, quick note, this is the Williams logo. Not the Motorola logo. They are awfully darn similar, but Williams made these relays in-house. So did Bally and Gottlieb - when you make thousands of pinball machines per month and each machine has dozens of relays, it definitely pays to roll your own.

See, they’re rolls of wire. Wire’s rolled around a hollow cor- anyway, moving on... Given what we’ve just learned about the game over relay and how one coil turns off the machine and the other coil turns it on, what do you suppose the coin switches in the coin door send power to to start the game? That’s right, the coin relay! Or maybe the 10 cent relay. Or even the 25 cent relay! OK, I’m skipping over all of the stuff you can do for different coin types and plays per coin. It involves the score motor and adjustment jacks and is a layer of complexity we just don’t need right now.

But it is in fact the coin relay that actually gets the ball rolling. And folks, explaining the next steps here is going to take a while. If you haven’t already gathered, a lot of stuff needs to happen when you insert a coin to play this game. The machine has various mechanisms throughout that may be in any number of configurations depending on how the last game went - including, of course, the score readouts. But we need them all to return to a known starting point before we can begin a new game. We are about to embark on a dissection of this machine’s reset sequence, and I regret to inform you that calling it a single sequence is quite the oversimplification.

So strap in. Up here on the schematic is the coin relay’s coil. It becomes energized by the coin switches, but as we’ve seen before, a switch within the relay provides a power bypass so the relay will lock on and stay energized even after the original signal from the coin switch is lost. The coin relay is also one of the many things that will start the score motor turning. And just like the 5,000 point relay we looked at in the last video, its power bypass goes through switch 5-b in the score motor. So here we have another example of a relay that locks on, starts the score motor, makes some stuff happen as the score motor turns, and releases just before the score motor returns to the parked position.

This unassuming little switch in the coin relay is what actually resets and starts the game. Looking at the schematic, you’ll notice that the circuit branches off at this point and meets another two switches. This switch here is in the score motor on switch stack one, and since it’s normally open, power doesn’t make it through just yet. The score motor has to move forward a bit to close this switch.

But power will make it through this switch in the game over relay. Now, you might very well be saying to me, “but that switch is drawn as open, dingus!” And you’d be right! But this particular switch is a confusing little bugger. Every switch in the schematic is depicted as either normally open or normally closed, which is obvious enough for nearly everything in the game.

Normal is defined by a switch’s resting position, so in the case of relays that means their position when the relay isn’t energized. But the game over relay doesn't have a single resting position, it has two resting positions! Its two separate coils flip it back and forth between one and the other. So, for the purposes of drawing that relay’s switches in the schematic, the drafters had to just pick one. And, unfortunately for us looking at this specific part of the game’s logic and sequencing, they decided to depict the game over relay in its latched position (meaning the game is on and in-play).

For most of the schematic that decision makes much more sense, but since I’m going through what happens to actually turn the game on, prior to inserting a coin the game over relay is in fact tripped and thus every one of its switches is in the opposite position from how it’s drawn. Therefore, at the moment you insert a quarter and the coin relay energizes, power does get sent up through here to the reset relay coil and so the reset relay pulls in. And just in case you’re not confused enough already, you should know that the reset relay isn’t actually responsible for resetting the game - it only resets the scores. I will explain that in a moment but for now we’re going to ignore that and focus on the next thing that’s about to occur.

Since the coin relay also starts the score motor turning, in just a moment switch 1-B will be pushed closed by the movement of cam 1 and a pulse of power will get sent through to all this stuff. Now you’ll notice that the reset relay is also involved here with these two switches. Why? Well, there’s some complicated interlocking going on here since this is a multiplayer game. For now, let’s pretend we’re just starting a new single player game.

Since the reset relay has been pulled in to reset the scores, this make-break switch will send power down this way and we’ll skip the coin unit step up coil. This switch is also closed so the upshot is that everything shown here except the coin unit step up coil will get actuated by the score motor through the coin relay. So now… what are these everythings? First, we have the total playmeter. That’s this odometer-lookin' thing which counts how many times the game has been played which is useful to know for lots of reasons, including gauging the need for servicing and auditing the machine’s cash intake. Then, remember, we’re skipping the coin unit step up coil.

Instead we hit the coin unit reset coil. Then there’s the game over relay latch coil (which, remember, actually turns on the game). And we also send power to reset the ball count unit and the player unit. What are all those units? Stepper units! That’s what you saw in the thumbnail and I mentioned in the beginning. These are the devices that allow the machine to count and/or change its behavior based on their physical positions. Stepper units come in three flavors: continuously stepping, step up/step down, and step up/reset.

Now, they might look pretty complicated but in reality they’re a pretty simple idea. In fact, score reels are technically a kind of continuously stepping stepper unit - a solenoid advances a ratcheting mechanism which moves the drum forward by 36 degrees. They are continuously stepping because they can only move in one direction and don’t have a defined end-point. But you don’t have to move a plastic drum with numbers printed on it - you could also move a series of wipers across a circuit board which will bridge contact patches together. And you can change the machine’s behavior based on what you wire to that circuit board. If you add a second solenoid to this mechanism which can step it in reverse, then you’ve got a step up/step down stepper unit.

This machine has two of those which we’ll be looking at later. But if the second solenoid resets the stepper to its starting position with a single actuation, you’ve got a step up/reset stepper unit. The ball count unit, coin unit, and player unit are all reset with a single pulse to their reset solenoids, so when the score motor and coin relay send a pulse of power to their reset coils, they all return to their starting positions in one fell swoop.

And that’s what the coin relay just did: in addition to switching the game on by pulsing the game over relay latch coil, it got all of the game’s critical stepper units reset to a known beginning state. The ball count unit was reset to ball one. The player unit was reset to player one. And the coin unit was reset to… single player.

Don’t worry about that right now. But also don’t forget that we have to return 20 other stepper units back to a known state - the score reels. I’m sorry we’re moving back and forth so much but what I’ve just described all takes place in a fraction of a second. [ka-CHUNK] It’s been a challenge to decide how best to go about this. Remember that the coin relay also sent power to the reset relay up here - but you’ll notice that there is in fact more than one reset relay: there are four, helpfully numbered one, two, three, and reset relay. For your sake, I’m gonna call those numbered fellas the bump relays 1, 2, and 3.

Trust me, that makes way more sense. The main reset relay, like so many others in the machine, will lock on through a switch within itself but this time its interlocking switch can get power from three separate sources. Did I say three? I meant 22. See, the primary thing the reset relay is actually doing is sending pulses through the score motor to those bump relays.

When the reset relay is energized, power flows through impulse switch D which will send pulses to bump relays 1 and 2, and a second branch flows through impulse switch A to pulse bump relay 3. And this is what that looks like: those three relays are clacking away in the backbox five actuations at a time. Of course, I’ve rigged this to keep on clacking nonstop.

Typically they only do this ten times and then the game is reset. What is it that those bump relays do? The switches within these relays send pulses of power to all of the score reels to repeatedly bump them, or advance their position. And each one of the score reels will stop automatically when it reaches zero. If you’re wondering how that could happen, remember the 9th position switch we saw in the last video? Well, I strategically ignored the other switches in that stack until right now because those are zero position switches. The little pivoting arm that pushes the switch stack up at the nine position swings the other way at the zero position and opens these two switches.

One of the switches connects the solenoid in the score reel to its respective bump relay switch. When it’s showing any number other than zero, that switch is closed so the score reel solenoid will repeatedly receive a pulse of power during the reset and thus keep moving forward. But once it gets to zero, that switch opens so the pulses no longer make it through to the score reel’s solenoid and it stops moving. The other switch in the switch stack is part of the interlock circuit of the reset relay. And every single one of those in the machine is wired in parallel so that if any score reel should be on a number other than zero, the reset relay will remain energized and thus it will keep firing the bump relays to get them to zero.

That means there are actually twenty-two different switches that can provide power to the reset relay - this switch in the index stack, this switch in the bonus relay, and the 20 switches in all of the score reels. Oh and look at that - there’s a mistake in the schematic! Somebody forgot how many score reels they were putting in this machine and said there were only 16 switches. How embarrassing! It’s a good thing schematics don’t have comment sections or they’d never hear the end of it. Jokes aside, that’s understandable.

It’s actually quite odd that this game uses five score reels per player. Most of its contemporaries only used four, and I have a hunch that since this machine was built during the development of the new solid-state control systems which would use digital display technologies, Williams realized that all of the score reel parts they had in their inventory were about to become obsolete. So they might as well start using five per player to try and get rid of ‘em. Aztec wasn’t alone in this, several other Williams games from 1976 such as Grand Prix and Space Mission also use 20 score reels per game, but as far as I can tell all games released in 1975 stuck with four per player, 16 total. So I bet that little slip-up on the schematic was simply out of habit. Anyway, in action the resetting of the scores looks like this: [CLACK CLACK CLACK CLACK CLACK ... CLACk CLAck CLack Clack clak]

Every score reel gets bumped until it shows zero. Since it should only take nine bumps at most to reach zero, two cycles of the score motor (with five bumps each) is enough to reset all the scores. [two sets of five clacks, diminishing as more reels reach zero] Once they’re all on zero, all of their zero-position switches are open, so the reset relay will de-energize.

If we look at the three bump relays during this sequence, you’ll see tremendous amounts of arcing going on when the machine resets, especially after a four-player game where nearly every score reel is off of zero. Now twenty solenoids all firing at the same time is a recipe for a blown fuse, so you might have noticed that the score reels were actually moving in two groups. It’s very subtle, but see if you can spot it. I’ll slow that down. This grouping is accomplished by the impulse-forward switch on the score motor. That switch, which the schematic designates impulse switch D, is positioned literally forward of the other impulse switch stack.

That way the two don’t get actuated at the same time by the movement of the cams below. Instead they alternate, and the number three bump relay fires before one and two. That breaks the score reel solenoids into a group of 12 and a group of 8, much more manageable current-wise. OK - so at this point, the game is on, the scores all show zero, and the stepper units the game needs to keep track of its program are all reset. So now what? Well, it needs to kick the ball out of the outhole and into the shooter lane so you can actually play the game. Let’s look on the schematic for the outhole kicker coil so we can find out what sends it power.

Apparently it’s called the ball release coil. OK, so it’s gonna get power from switch 4-B in the score motor, but only if this switch in the outhole relay is closed. [sigh] so let’s find the outhole relay then.

Oh, it’s right up here. OK so that relay’s got its own switch to lock it on (of course it does), and like so many other things that power path will eventually be broken by switch 5-B in the score motor. But what gives it the initial pulse of power is… the… um… what’s all this? Why is it going through the bonus relay… and the bonus unit zero position switch? I’ll tell you why: it’s another utterly confusing thing! The outhole switch - that is, the switch the ball closes when it lands in the outhole - energizes the bonus relay, not the outhole relay. The outhole relay, in turn, is energized by the bonus unit’s zero position switch. For now, we’re gonna ignore the bonus unit.

I promise this is going to make sense eventually. So - we’ve inserted a coin. The game and the score have reset We’re on ball one and player one is up. The bonus unit was in the zero position, so the outhole relay did get energized which caused the ball release coil to be fired when switch 4-B of the score motor was actuated. And now the ball is finally in the shooter lane and the game can be played. But now, I’m going to put the ball back into the outhole - watch what happens.

[several mechanical noises in a rhythmic sequence] The ball was sent back to the shooter lane after two cycles of the score motor, and the ball-in-play did not change. We’re still on ball one. I can just keep doing this forever [that same rhythmic sequence] and the game will keep serving me the ball again and again. Why is it doing this? [KA ch ch ch ch ka-CHUNK ch ka-CHAKA clunk] Well, suppose the ball release coil is getting weak or the mechanism is gummed up in some way.

It may not get the ball into the shooter lane on the first try. The designers foresaw that possibility (or, more likely, older games screwed this up and they learned a lesson) so they designed an interrupt into the program which prevents it from advancing to the next ball until the ball has actually hit a target. That interrupt is in the form of a relay, would you believe it? And that relay is the ball index relay. This is the relay itself, and this is where it lives on the schematic. This relay is connected to switches in the 10, 100, and 1,000 point relays. In this particular game, the ball must hit at least one target worth those point values as it enters the playfield: if it doesn’t hit a 100 point rollover button, it may hit the 10 point bumpers, and if it misses both it will absolutely go through one of the 1,000 point rollover lanes.

hat means that technically the only relay that needs to activate the ball index relay is the 1,000 point relay, but all three can activate it most likely for redundancy in case one of those switches gets dirty or fails. Anyway, here’s why it’s important: until this relay is energized, the game does not consider the ball to have made it to the playfield, and it will not increment the ball count if the ball ends up in the outhole. It will just keep trying to serve the ball to you over and over again. But once it does, you’re free to have a ball and play the game. Since I’ve already gone over how all the stuff on the playfield works, we’re not going to get into much at all here. Except for this: Advance Bonus.

Some of the targets advance the bonus value, shown by this arc of illuminated inserts on the playfield which us pinball nerds call the bonus ladder. Every ball begins with 5,000 points which will be awarded at the end of the ball, but you can increase the bonus value by hitting the targets that say “advance bonus.” Watch what happens when I hit the center rollover button. [clack] We hear a click, and the next light on the bonus ladder is now lit. That click: [clack] It came from, well two things actually: the advance relay and the bonus unit step up coil.

The bonus unit lives on the underside of the playfield, not too far from the bonus ladder, as it turns out. You may notice that there's a pretty large crack in it. Did I do that? That’s not important. This is a step up/step down stepper unit.

One solenoid moves the wiper arms forward by one step, and the other moves them backward by only one step. This has eleven possible positions: zero, 5,000, 10,000, 15, 20, 25, 30, 35, 40, 45, and 50,000 points. The contacts and wipers here are mostly used for the indicator lights in the playfield.

These bonus lights are wired to these little studs, and the wipers connect each individual light up to a power source as they move - thereby showing how many steps away from the zero position the bonus unit’s mechanism is. The player doesn’t realize that’s what’s going on - they just know how many bonus points they’re due at the end of the ball. But you know that’s what’s going on because I just told you. That’s the critical piece of information here: “how many steps is the mechanism away from zero?” That in and of itself is what’s totaling the points to be awarded. To explain how that works, let’s say there’s 15,000 points on the bonus ladder and you lose your ball.

The ball’s gonna end up in the outhole and land on the outhole switch. When it closes, power that’s coming from the score motor and traveling through this switch can finally make it through and energize the bonus relay coil. That relay will lock on through this switch here, and then… well it's got to award 15,000 points. To find out how that happens, we need to look at the 1,000 point relay. In addition to all the stuff down here that we looked at before, there’s a path through the double bonus relay and this bonus relay switch and the ball index relay to this grey and white wire up at D-7.

And what we find once we go up there is impulse switch C. Since that’s going to send five pulses of power through as the score motor turns, the 1,000 point relay gets actuated five times and 5,000 points are added to the score. But of course we’re not done - and indeed, adding those points isn’t all that happened. Watch how this sequence actually occurs.

[five dings, then a clunk] Just after the 5,000 points are awarded, we hear a clunk and the bonus ladder moves down to 10,000 points. That clunk was the bonus unit reset coil moving the stepper unit’s wiper arms back one notch. Let’s find that on the schematic so we can see why that happened. Here we are - that coil gets its power through switch 5-A in the score motor.

That then travels through a make/break switch in the double bonus relay, before hitting the switch in the bonus relay. Because of the sequencing in the cams of the score motor, switch 5-A is actuated just after the fifth pulse of the 1,000 point coil. So, as we saw, we got 5,000 points, then the bonus unit moved down to 10,000 points remaining. Now the ball is still in the outhole, and the bonus unit is still not in the zero position. So what happens next? The same exact thing.

The 1,000 point relay coil gets five pulses, awarding 5,000 points, and just after the fifth pulse the bonus unit steps down and now 5,000 points remain. Since it’s still not at zero and the ball is still in the outhole, we repeat this once more and our 15,000 points have been awarded. [five dings, then a clunk - repeated three times] However, after those last 5,000 points are awarded the bonus unit reset coil is still going to get pulsed. Once it gets that pulse, it’s going to move and end up in the zero position. And now, things change.

Remember how the bonus relay was getting power? It initially came through this make/break switch marked “bonus unit zero position switch.” At zero, power is redirected, disconnecting power from the bonus relay coil and instead sending power to the outhole relay coil. Also of note, the bonus relay’s power bypass went through a zero-position switch in the bonus unit, too, so once the bonus unit has made it to the zero position, the bonus relay is de-energized and effectively locked-out.

So now, what happens next? We know the outhole relay has been energized, but without hunting through the schematic to find every outhole relay switch, how are we to know what it actually does? Well, we do know three things are going to happen for sure: it needs to give the ball back so ball two can be played, it also needs to reset any of the relays that might have been triggered in the last ball (like the AZTEC relays, and let’s not forget the ball index relay), and then it needs to move the ball-in-play from one to two. Let’s look at those one at a time, starting with those relays. That’s actually pretty simple. Every relay which locks on through the course of a ball-in-play but resets when a new ball begins is wired through this normally-closed switch in the outhole relay. As soon as the bonus count is finished, those relays will all release since the outhole relay becomes energized and opens this switch. And sure enough, that’s what we see.

[ten dings as bonus is counted down, then several clunks] Since it also has to give the ball back, let’s revisit the ball release coil. We’ve already looked at that before, and it is pulsed by switch 4-B in the score motor through the outhole relay just like it was when it delivered the first ball of the game. But now, since we have played through the first ball, it has to move the ball-in-play from one to two. That’s handled by the ball count unit which lives here in the main cabinet.

It’s another stepper unit but this one only has two wipers, both of which are wired to the common ground back to the transformer. To explain what that means, this arm light up the ball-in-play lights on the backglass. And there’s actually voltage going through the light bulb filaments all the time - the only reason they aren't all lit right now is that wires for each bulb are broken right here. They reach a dead end at the contact patches.

The wiper arm, though, will complete the circuit once it touches the patch. The corresponding light, then, becomes lit depending on the position of the ball count unit’s arms. Oh, and by the way - I do appreciate how Williams arranged the lights in the order 1, 4, 2, 5, 3.

Since this can be set to three-ball play, it would probably make you feel a little ripped off if the last ball shown was in the middle of this yellow box. Clever thinking. The other wiper and contact patches on this stepper? Those come into play at the very end of the game.

See if you can guess what they complete a circuit to. As a refresher, this is a step up/reset stepper, and its reset coil was pulsed at the beginning of the game to return it to the ball one position. But now we’ve played ball one, the bonus points have been awarded, and it needs to move to ball two.

Let’s find the ball count unit step up coil. That’s up here - and now you’re going to get a clue about how this machine handles multiplayer games. The circuit path for the ball count unit step up coil is about as convoluted as it could be. Power goes through the outhole relay, then the extra ball relay, then the ball index relay, then switch 1-C in the score motor, then it takes one of several possible paths through the player unit and coin unit before finally hitting the coil which moves the ball count unit up. But all we need is a single pulse, and once it’s sent through it moves to the next position.

And now, ball two is shown on the backglass and the ball is back in the shooter lane to be played again. Everything in the game is exactly as it was in the very beginning other than the score reels for player one being… wherever they happen to be depending on how well you did and the ball count unit being in the second position which illuminates the 2 on the backglass. You play ball two, the first target the ball hits energizes the ball index relay, the rest of the ball goes how it goes, and when you lose the ball the exact same sequence we just went over will happen again. The outhole switch energizes the bonus relay, which will award 5,000 points then step the bonus unit down.

It repeats that until the bonus unit hits zero, at which point the bonus relay becomes locked out, the outhole relay takes over, whatever relays that locked on in the prior ball are all released, and the score motor sends pulses of power to several things in-sequence including the ball count unit to move to ball three and the ball release coil to send it back to the shooter lane. Simple! But I’ve forgotten something. Every ball begins with 5,000 points on the bonus ladder already. That means the bonus unit step up coil must be getting pulsed by the outhole relay at some point in its sequence.

And sure enough it is, through switch 3-b in the score motor. This explains why if the ball lands in the outhole before it hits a target on the playfield, it takes two cycles of the score motor for it to return the ball to you. [five rapid ticks, a clunk, then more ticking and clunking] What actually happened just there is the same exact sequence as if you had lost the ball - the outhole switch energized the bonus relay, and it attempted to award 5,000 points.

That takes one cycle of the score motor, and the bonus unit reset coil was pulsed at the end. Then, with the bonus unit in the zero position, the outhole relay took over. It’s no different from any other ball drain.

However, since the ball never made it onto the playfield, these open switches in the ball index relay prevented it from actually awarding those 5,000 points while the bonus relay did its thing and from incrementing the ball count when the outhole relay returned the ball. Pretty clever. But let’s get back to where we were. We are on ball three, and this time let’s say you score an extra ball during play. That becomes possible when all of the AZTEC letter targets have been hit.

And, quick note, that’s affected by the game’s difficulty adjustment which we find here in the schematic. I am not going over that. But when set to conservative, as it is now, once all of the AZTEC relays are energized, the center target becomes lit for an extra ball by the setup relay. That lights the “when lit” light and also closes this switch.

If you manage to hit the center target, then, a pulse of power is sent to the extra ball relay which then locks on until the end of the ball and lights up the "same player shoots again" lights both in the backglass and on the playfield. How does that give you an extra ball? You may remember that one of the things in that convoluted circuit path which incremented the ball count unit was a normally-closed switch in the extra ball relay. Since, once you’ve earned an extra ball, that switch becomes open… well the pulse from the score motor that would increment the ball count unit after the bonus countdown simply doesn’t make it through. The game will do everything it normally does at the end of a ball, including awarding the bonus and returning the ball to you to be played again, but it won’t move the ball count unit. It will just stay where it was.

It also doesn’t send a pulse through to the player reset relay, but that’s not important right now. The extra ball relay’s interlock path goes through all the point relays as well as the ball index relay, so once you get an extra ball, the “same player shoots again” lights remain lit until the same player shoots again and the ball actually hits something. The last thing I want to touch on is what happens when you activate double bonus. You score double bonus by hitting either of these targets after hitting the Z or T targets - when both conditions are met, that will activate the double bonus relay. We’ve already seen the double bonus relay’s switches come into play a few times in this video, but what they actually do is quite interesting. First, of course, it lights up the “double bonus when lit” indicator.

But it also radically changes how the bonus sequence occurs at the end of the ball. Notice that this make/break switch connects the bonus unit reset coil to impulse switch B in the score motor. That will make it rapidly fire five times with each score motor rotation. We also find that this make/break switch redirects power from the 1,000 point relay to the 10,000 point relay. In action, this means that the awarding of your bonus points happens much more quickly when double bonus is lit. Since each spot on the bonus ladder is now worth 10,000 points rather than 5,000, only a single pulse to the 10,000 point score reel is required per lit spot on the ladder.

So the process is really quick, taking at most two cycles of the score motor. [five rapid clunks, then three] [more clicks as it resets for the next ball] Of course, once the bonus unit reaches the zero position, the bonus relay releases, the outhole relay takes over, and the same end-of-ball sequence we’ve been looking at happens once again. Which, by the way, will remove power to the double bonus relay coil so... too bad on your next ball. I’m about to wrap this video up because runtime, but I want to focus on the word sequence.

Remember that the score motor’s numbered switch stacks are actuated one-at-a-time. In this clip, I’ve filmed the score motor in low-light so you can see how the arcing appears to travel from left-to-right. [rapid clicking and clacking] All of this is all happening thanks to the outhole relay - that one relay connects five things to these switches and they are each actuated in order. Some of them we’ve already touched on - others we haven’t. But the order of operations is critical here because each action that takes place might change the next.

The very first thing the outhole relay makes happen is push a pulse through switch 1-C to increment the ball-count unit. And after the last ball, that is the action which shuts off the game. Since this is currently set to three-ball play, once the ball count unit moves into the position for ball four, the other wiper completes the circuit for the game over relay trip coil. The instant it moves to ball four, the game shuts off.

You can see that if I bridge this switch together, despite being in the game over position, ball 4 lights up on the backglass. The ball count unit is actually resting in the ball four position. But the 3 or 5 ball play adjustment jack has connected the game over relay trip coil to this contact patch, so as soon as the wiper touched it, boom. Game over. If I had set this to five ball play, it wouldn't have ended the game because in that case the game over relay trip coil is connected to this contact patch instead. So you would get to play ball four.

And then ball five. At the end of ball five, though, the ball count unit would step up again and in the quasi-sixth position, the game over relay would be tripped. With the game over relay tripped, the rest of the stuff the outhole relay normally does at the end of a ball... just doesn’t happen. For instance, the ball release coil doesn’t get power since this switch is now open. In fact, none of the stuff below this point in the schematic will work.

The game is over so it's shut off. But there is a different thing it might do at the end - and that is give you a free game. If the number at the end of your score happens to match the number that appears in the clouds on the backglass, you’ll hear a knocking sound and suddenly the number 1 will appear here, indicating there’s a credit on the machine, and a new game can be played by pressing the start button. How’s that work? Well… I guess we’re gonna need a part three.

I know, I know, but there’s a lot to this! We’re almost there, though. In part three, we’ll take a look at how this number match feature works. We’ll also look at the credit unit (did you know that that’s what made pinball illegal in some places? Yeah, and we’ll get into that, too). We’ll also look at how multi-player games work, and finally we’ll talk about the tilt switch. Get too rough with the machine and boop - you’ve lost that ball.

Better luck next time. Speaking of next time, see you next time! ♫ tiltedly smooth jazz ♫ In the perhaps ostimi… [disappointment] well... already got one! ...that the primary reason for their existence isn’t fun. It’s… something weird happened.

Mmmneergahbuhguhbuhbuhgaaaaah buhbuhbugabowwwah The main relay like -- AAHHHH But you’ll notice that the… BLARGRRP! But one that mechanically latches into two stable… crap! Not the Motorola logo. Ble…mmmm okay, this is a long line. Gotta start at the bottom. …like so many others in this machine will lock on through a switch within itself but this time its interlocking power path oh crap.

Did you get the two bits of trivia pun? Honestly I doubt even many Americans would. "Two bits" is an old expression for a quarter. That's what "shave and a haircut: two bits" means. The best jokes need explanations.

2023-12-30 11:11

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