Photo: MOSFET lamp drivers with jumper wires

A reference photo of a Williams driver board with its lamp driver transistors replaced by P-channel MOSFETs (the file names IRF9Z34 or FQP17P06), each with a short wire jumper fitted beside it, as in the lamp MOSFET upgrade.

Systems

• Williams System 3
• Williams System 4
• Williams System 6 / 6A
• Williams System 7

Related tips

• MOSFET lamp column upgrade
• Lamp matrix wire colours and connector pins
• Diode-test the lamp pre-drivers (2N6427/MPSA14)
• How the lamp matrix runs 6.3 V bulbs on 18 V
• Tester LED check of the lamp columns
• Tester LED check of the lamp rows
• Diode-test the lamp column and row transistors
• Light a lamp row by grounding its transistor

Source: MOSFET jumper (IRF9Z34 or FQP17P06)