A ball through the right outlane sometimes acts like the start button, adding players on ball 1 or starting a new game later. It happens with a known-good MPU and with the coin door unplugged.
Right outlane adds players or starts a new game: start button shares a matrix row
Cause: The credit/start button is in the switch matrix (it appears only on the wiring diagram, not the matrix chart), and a failing diode on a switch in its row let the outlane switch ghost onto it.
Checks
- Find the start button's row and column on the wiring diagram.
- Test the diodes and switch capacitors on every switch in that row; a diode can test good and still misbehave.
Fix
- Replace the diodes (and small switch capacitors) on the switches in that row.
Systems
Games
Related tips
- Tilt doesn't work and closing it fires a pop bumper: dirty slam tilt switch
- Strange game behaviour from a grounded start button
- Self test will not start from the coin door button
- Switch matrix confused by a bad MPU DIP switch diode
- Player 1 display shows credits and ball in play
- Coin door switch shorted to ground causes lamp and other odd faults
- Several playfield switches drop out together: worn insulation shorting the start button
- Prove the MPU switch inputs with the harness unplugged
Source: Pinball Repair help group!! (Facebook group)