Checking a filter capacitor for ripple

Steps

• Game on, meter on AC volts (low range).
• Put the leads across the capacitor; polarity does not matter.
• More than 0.20 V AC means the capacitor is bad (some use 0.10 V as the limit).
• For C5 on an installed board, clip a lead from the "+" terminal of BR2 to the red probe and put the black probe on ground.
• A bad bridge also shows high ripple, so it is often simplest to replace C5/C4 (C9/C1 on WPC-95) whenever the 5 V rectifier is replaced.

Systems

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

Related tips

• Driver board filter capacitors wear out
• Filter capacitors and GI triacs that fit WPC boards
• WPC-95 filter capacitors are smaller (10,000 mfd)
• +20 V filter capacitor C11 (C10 on WPC-95) blows apart
• Pre-WPC-95 bridges, filter caps and fuses by supply
• WPC-95 rectifier diodes, filter caps and fuses by supply
• Won't start after a power surge, 5 V reads very low: failed C4 on the power driver board
• Check fuses F106/F101 with no lamps and no game start: shorted bridge diode

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