Random resets continue after a bridge job, and the GI is only full on or off in the GI test (no dimming).

Resets and GI that will not dim after BR2 was replaced

Cause: Diodes D3 and D38 of the zero-cross circuit (just below J109) take their AC from the BR2 traces; the traces to them are easily torn when BR2 is changed.

Checks

• Go to the GI test: if the lamps do not dim at lower levels, a D3 or D38 trace is broken.
• With the meter, buzz the upper-right BR2 lead (component side) to the right end of D38, and the lower-left BR2 lead to the right side of D3.

Fix

• Repair the broken trace with a wire jumper.

Systems

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

Related tips

• Resets continue although the bridge and diodes test good
• Resets or dead banks of coils or lamps from cracked bridge or cap solder
• What a WPC game reset is
• Pre-WPC-95 resets: replace BR2, C5, C4 and the J101 pins together
• Watching the supplies while the game resets
• Resets when the knocker fires, hum and DMD glitches: cracked power board joints
• Raising the WPC/WPC-S +5 V to about 5.15 V (last-resort reset fix)
• Resets: +5 V at the driver board test point is low

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