System 9 CPU and sound test EPROMs

Steps

• Program the System 9 CPU test file and sound test file each into its own 27128 EPROM.
• Power the CPU board: ground to 1J17 pin 1, 2 or 3; +5 V to 1J17 pin 4, 5 or 6; and +5 V to the anode (top) of VR1, right of the batteries (a jumper from 1J17 pin 6 is easiest).
• Fit the CPU test EPROM at U20 (true for every System 9 game whatever the jumpers).
• A good board shows 0 and 7 alternating on the LED digit. PIAs U15, U14, U4 and U5 should toggle pins 2-17, except U5 pin 9 (grounded) and U15 pins 2-9, which need J10 pins 1-9 grounded.
• Press SW1 (near 1J14) for the memory test: the display stops briefly and restarts if U18 is good; a steady 0 or 7 means a memory fault.
• Sound section (CPU U11, PIA U13, RAM U12, EPROM U49, amp U59, DAC U48): fit the sound test EPROM at U49, keep the game ROM at U20, check U11 pin 15 toggles and U13 outputs move, then press SW2 (near 1J16): outputs pause and restart if U12 (6810) is good.

Systems

• Williams System 9

Related tips

• Which System 11 CPU boards fit which games
• System 9: Sorcerer uses two game EPROMs, Comet and Space Shuttle one
• System 9: is the sound fault on the CPU board or the speech board?
• System 9 and System 11 seven-segment LED codes
• Where sound is made on System 9 and System 11/11A
• System 9 versus System 11 display data
• System 11 switch matrix: connectors and chips
• System 9 reset section parts after battery corrosion

Source: Repairing Williams System 11 Pinball 1986 to 1990, Part Two, Clay Harrell (pinrepair.com)