Firing a coil by grounding its TIP102 tab

Steps

• Only do this on TIP102 transistors; it can damage TIP107 or TIP36 parts.
• Game on, press the test button once; coin door closed on 1993 and later games.
• Remove the backglass and find the coil's TIP102 from the manual.
• Clip a jumper to the ground strap in the bottom of the backbox and briefly touch the other end to the TIP102 tab.
• If the coil fired when grounded at the coil but not here, suspect a broken wire or bad connector pin between board and coil, or the transistor itself.
• If both tests fire the coil but the game cannot, the fault is the TIP102, its pre-driver or the logic chip feeding them.

Systems

• WPC Alpha-Numeric
• WPC Dot Matrix
• WPC Fliptronics
• WPC DCS
• WPC-Security (WPC-S)
• WPC-95

Related tips

• 20-second check for shorted TIP102s
• Testing a coil diode on the driver board
• 20-second test for shorted coil driver transistors
• Where the WPC coil and lamp drivers sit
• How a WPC coil, flasher or lamp driver chain works
• Testing TIP36c, TIP102, TIP107 and pre-driver transistors in the board
• Supercharger diverter dead even in test: open TIP102 at Q81 that tested good
• Auto-launch fires weakly but full power when the transistor is grounded

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