Continuity checks after replacing GI header pins

Steps

• Power off; unplug J115, J119, J120 and J121; measure on the component side.
• J115-1 to ground (a break here causes erratic GI dimming).
• J115-2 to F106 to pin 11 of J120/J121 and J119-1; J115-3 to F110 to pin 7; J115-4 to F109 to pin 8; J115-5 to F107 to pin 10; J115-6 to F108 to pin 9.
• J115-7 to Q10, whose middle leg goes to J120/J121 pin 2; J115-8 to Q18, middle leg to pin 1; J115-10 to Q16, middle leg to pin 5; J115-11 to Q14, middle leg to pin 3; J115-12 to Q12, middle leg to pin 6 and J119-3.

Systems

• WPC Alpha-Numeric
• WPC Dot Matrix
• WPC Fliptronics
• WPC DCS
• WPC-Security (WPC-S)

Related tips

• GI string still dead after replacing J115: broken through-hole, add a jumper
• Two GI strings still dead after fixing a burnt J120: broken pads and traces
• One GI string dead though the board and fuse test fine: burnt connector in the cabinet
• GI string dead after connector replacement: broken traces
• One GI string dead after a restoration: unkeyed J115 plugged in upside down
• Several GI strings dead after a connector repair: lifted pads at J115
• All GI out (playfield and backbox) with good fuses and plugs: reseat the CPU ASIC and ROM
• All backbox lights out with good fuses: burned J120 GI connector

Source: Repairing Williams/Bally WPC Pinball Games from 1990 to 1999, Part One, Clay Harrell (pinrepair.com)