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.
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
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