20-second check for shorted TIP102s

Steps

• Game off. Meter on resistance or continuity beep.
• Hold one lead on the backbox ground strap.
• Then probe the metal tab of each TIP102.
• A beep or zero ohms means that TIP102 is shorted on. This shortcut only works for TIP102s.

Systems

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

Related tips

• 20-second test for shorted coil driver transistors
• Firing a coil by grounding its TIP102 tab
• Testing TIP36c, TIP102, TIP107 and pre-driver transistors in the board
• Coil locks on as soon as the coin door closes: transistor shorted by the old coil
• Supercharger diverter dead even in test: open TIP102 at Q81 that tested good
• Left popper fires at random with the right pop bumper: shorted J127 header pins
• WPC driver board: lamps, GI and coils all dead, CPU fine: broken blanking trace
• No insert lamps at all, lamp supply fine: broken trace under a driver board capacitor

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