After removing a hard-wired volume pot that a previous owner had fitted, there is no working volume: the coin door buttons change the volume display but the sound level does not follow. All the sounds play if a fixed resistor or pot is put in instead.

WPC-89 sound board: digital volume control does nothing: broken trace at the X9503

Cause: Part of the trace leading from pin 6 of the X9503 digital potentiometer (U5) was missing, so the digital volume circuit was open.

Checks

• Measure the resistance between pins 5 and 6 of the X9503 while stepping the volume up and down: it should change. No reading at all points to the chip or its traces.
• Check that jumper W9 is in its stock state, and inspect the traces around the X9503 and the MC3340 attenuator closely.

Fix

• Repair the broken trace from the X9503 (and replace the chip if it still doesn't respond).

Systems

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

Related tips

• Right backbox speaker silent while the left works: failed tweeter capacitor
• Volume stuck at full and buttons do nothing (pre-DCS)

Source: Pinball Repair help group!! (Facebook group)