Fitting a manual volume pot to the A-12738

Steps

• Remove jumper W9 to disconnect the software volume control.
• Wire a pot of any value from 5k to 200k ohm to J507: pin 2 to the centre leg, pin 4 (analog ground) to an outer leg.

Systems

• WPC Alpha-Numeric
• WPC Dot Matrix
• WPC Fliptronics

Related tips

• Pre-DCS sound board A-12738
• Adding a line out to the A-12738 sound board
• Volume stuck at full and buttons do nothing (pre-DCS)
• Sound board fuse F501 blows at power-on (A-12738)
• Sound board beep codes before DCS
• Pre-DCS sound cuts out after the game warms up
• Pre-DCS speakers pop and get damaged, LM1875 runs hot
• Pre-DCS sound boards are tuned per game

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