How CPU-controlled lamps are driven

There is no lamp matrix. Each of the 36 CPU lamps has its own driver transistor, fed by nine 74175 latches. L1-L4 use MPS-U45s, which can run two bulbs or pre-drive a coil transistor; L5-L36 use MPS-A13s (Q5-Q24 and Q33-Q44) that run one bulb each.

Systems

• Gottlieb System 1

Related tips

• No CPU controlled lamps light
• Testing a CPU lamp circuit by grounding its driver
• Finding which transistor drives a lamp
• All CPU controlled lamps are dim
• Shorted lamp sockets kill MPS-A13 drivers
• Groups of four lamps or single lamps misbehaving
• None of the CPU controlled lamps light
• A CPU controlled coil does not fire

Source: Gottlieb System 1 Pinball Repair from 1977 to 1980, Clay Harrell (pinrepair.com)