Mr. Pinball Tip:

Reading an electromechanical schematic is not difficult once you understand the symbols. Each schematic contains common elements and follows certain conventions as described below.

The schematic is not a wiring diagram. It represents a logical description of the machine's electrical circuits. Being such it will represent lamps, motors, switches, coils, and so on--but will not represent connectors, mechanical hardware, or cabinet locations. This other information is usually contained in the manual or parts catalog, but sometimes appears as a side note on a schematic.

A pinball machine is composed of many, many circuits, and the schematic groups them in a way that is relatively easy to follow. Most machines run 2-4 main circuit groups. Each of these groups, of necessity, is grouped on the schematic. These groups are high voltage (110 VAC), lamps (6.3VAC), relays (24-50VAC), and solenoids (24-50V). Sometimes the relays and solenoids run on the same 24-50V group. Sometimes just some of the solenoids (flippers and bumpers) run on a higher voltage or direct current group for more power. There are some exceptions to these generalizations, but by far this covers most games.

You can easily see these groups by looking at the schematic, and identifying the transformer, noting this is where all the different voltages and groups meet.

Wire Colors
All machines use color coded wiring to help identify wires. A wire color code is constant unless it comes to a switch or load (lamp, motor, coil, etc.), at the other side of which it would change. This means that a wire color is the same on both ends of a connector. Remember--connectors are not represented on the schematic.

Prior to the 70s most schematics used color numbers. Since then most have either color letters or abbreviations to designate wire colors. Be careful of code 'B'. It can represent black or blue, depending on what other codes are being used. 'G' is another ambiguous color code since it can mean gray or green. Gottlieb used 'S' for slate to avoid this problem. Color number codes are consistent among manufacturers and can be a pain to remember. Here's the table of color numbers, just in case you need them.
1 = red          6 = brown
2 = blue         7 = orange
3 = yellow       8 = black
4 = green        9 = gray
5 = white        0 = no trace color
                 J = jumper (color irrelevant)
The color listed in the codes is the base color. The second is the trace color. Sometimes you will have two trace colors. For example, 15 is a red wire with a white trace, 30 is a yellow wire. Be aware that many of the color codes are reused in the game. This reuse is usually denoted by a dash and they a third number.

Yellow, Black, and Red-White are the most common wire colors by far for power & ground in most machines for most circuits.

Note: On some games the red tint in the insulation fabric has faded and looks more like a faded orange, salmon, or cream. So a red-white wire sometimes looks like a salmon-white wire. This problem doesn't seem to be limited to one manufacturer.

The fuse symbol should have a rating next to it. The coil symbol represents both relay (solid core) and solenoid (hollow core) coils. Sometimes you will see the coil symbol reversed to distinguish between relay and solenoid coils. The hollow lamp symbol is the most recent and most common. The motor symbols vary quite a lot among manufacturers.

A normally open switch means that the switch is open when the switch or relay upon which it is mounted is at rest. A normally closed switch means that the switch is closed when the switch or relay upon which it is mounted is at rest. A make break switch means the common pole connects to one of the other two poles, but never more than one. On this type of switch one of the connections is normally open and the other is normally closed.

Sometimes you will see a circle surrounding a switch. This means the switch is located on the motor assembly. Usually there will be a number and letter designating the position of the switch on the assembly. Some manufacturers, Gottlieb in particular, has a location code for motor switches that does not always uniquely identify a particular switch, only the switch stack. From that point you need to check the wire color codes or look at the motor diagram stapled to the inside of the cabinet to identify the switch.
The above representation means the same as the previous switch description and is used on very old schematics, usually those older than 1965. These kind of switch symbols are very difficult to read and understand!

The wiper unit disk is used on bonus units, 0-9 (00-90) units, match units, player units, coin units, ball count units, etc...all stepping units. The option plug is usually for game options such as liberal-conservative, 3-5 balls, match on-off, coins per play, and so on.

Connection symbols have changed over the years. Pay attention to which type you have. It makes a big difference!

You may run across a few other symbols, all of which should be labeled so you can tell what they are. You may also see slight variations in how some symbols are drawn.

A dashed line represent optional wiring, usually coin circuits. A dashed box, or solid box around some connections represent a single disk on a bonus unit, match unit, etc.

The state of the machine in the schematic depends on the manufacturer. Some represent the game with power on in game over mode. Others represent the game started with the ball at the plunger. Some even represent the game without any balls! Some games, usually 70s Gottliebs will tell you what machine state the schematic represents.

Schematics prior to the late 60s were mostly hand lettered and drawn. At least some prototype schematics for later machines were also hand lettered and drawn.
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