Driver board filter capacitors wear out

Expect about ten years from an electrolytic filter capacitor. A tired one leaves ripple on the DC and causes resets, so when BR2 is replaced on a pre-WPC-95 board also replace C5 (15,000 mfd 25 V). C4 (C1 on WPC-95), a 100 mfd keep-alive capacitor behind the LM323K, also dries out; replace it with 470 or 1000 mfd, never more than 1000 mfd, which overstresses the regulator.

Systems

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

Related tips

• Choosing a replacement driver board filter capacitor
• Getaway: beacon runs nonstop in test and driver board C11 overheats
• Pre-WPC-95 resets: replace BR2, C5, C4 and the J101 pins together
• Checking a filter capacitor for ripple
• Filter capacitors and GI triacs that fit WPC boards
• Driver board LED5 off (+20 V flashers)
• WPC-89/WPC-S driver board LEDs and test points
• WPC-95 driver board LEDs and test points

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