How driver board coil transistors are switched

Each coil driver transistor gets a positive pulse from the control board through a 1N4148 diode; the diode also protects the control board if the transistor fails. Three high-current coils use a transistor pair: an MPS-U45 drives a 2N3055, which switches the coil.

Systems

• Gottlieb System 80
• Gottlieb System 80A
• Gottlieb System 80B

Related tips

• System 80 driver board transistor types
• Optional ground mod step 1: ground the 2N3055 cases on the driver board
• A CPU-controlled lamp or coil stays on
• Spare diodes for coils and switches
• Which transistor types sit where on the driver board
• Flippers dead during play: check the "U" relay
• Haunted House trap door won't open
• A driver board output is stuck on or dead

Source: System 80 Service Manual, Gottlieb