Gottlieb Free Play Modification

Early Gottileb solid state pinball machines, prior to 1990, did not have a free play option available within the game settings.  With this simple modification, a game can be set up for free play.  First, identify the diode strip in the bottom of the cabinet.  Once the diode strip is found, locate the credit button and coin switch strobe line wires.  The wires will be located on the left of the diode strip - the non-banded side of the diodes.

System 1 diode strip location
System 80 diode strip location

Gottlieb System 1

Credit button wire - Green-White or Brown-Yellow-Yellow
1st coin switch wire - Orange-White or Brown-Red-Red
2nd coin switch wire - Brown-White or Brown-Orange-Orange

Gottlieb System 80

Credit button wire - Green-Yellow-Yellow
Left coin switch wire - Green-Brown-Brown
Center coin switch wire - Green-Orange-Orange
Right coin switch wire - Green-Red-Red

Solder a small lead wire from the credit button wire to any of the coin switch wires.  Make certain that the diode, credit button wire, and coin switch wire are still soldered securely to the diode strip terminal when finished.  If soldering is not an option, use a small alligator clip test lead.  Now, when the credit button is pressed, a credit will be incremented and decremented.  A game can be easily started without the need to open the coin door to trip the coin switches anymore.