Want to know which transistor drives which coil on your System-1 machine? Which transistor drives which lamp? Got a coil that won't fire or a burned out lamp or two? Here's a bunch of tables for as many Gottlieb System-1 machines as I have schematics for that will help you figure out which component is at fault.

I plan to add more machines as time permits and as I get more information. If you have information on machines that I don't have listed here, please send it to me and I'll post it here too.


Gottlieb System-1 pinball machines use a single driver board to drive both solenoids and lamps. These driver boards use transistors to drive both lamps and solenoids and depending on the load of the circuit, these transistors, and their quantities, are as follows (typically):
MPS-A13 (32 each) - Single lamps
MPS-U45 (5 each) - Multiple lamps or relay coils
2N6043 (7 each) - Solenoid coils
2N3055 (1 each) - High powered solenoids
The single 2N3055 transistor (Q45) is actually driven by an MPS-U45 (Q29), due to the high power demand of the associated solenoid, which is more than the MPS-U45 can handle. This single driver circuit was designed for a single solenoid that required a lot of power to energize (for example, resetting a bank of 5 drop targets). Unfortunately, the need for additional high powered driver circuits arose and presented a problem, since the driver board only had 1 such circuit. To solve this deliema, Gottlieb placed additional high power driver transistors underneath the playfield near the desired coil(s), then used one of the MPS-A13 circuits on the driver board to drive the high-powered transistor under the playfield. This high-powered transistor then drives the solenoid. These transistors and the ones on the driver board are easy to replace once the defective ones have been identified. Although Clay's System 80 Repair Guide does not deal with System-1 driver problems directly, the principals are the same as far as testing the transistors on a System-1 Driver board, so you can use this guide to help identify the bad transistors on your System-1 driver. If you'd like to find out which driver transistor goes to which driver connector tab, Click Here.

Click on a machine to see the info:

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Created 9/12/02 - Last Modified 8/1/07 - Steve Kulpa Mail Icon Nolensville, TN
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