Quoted from Quench:
Your problem is different - you are not getting normal tone sounds at startup or during game.
Seems to me you likely have poor ribbon cable connections at the MPU and/or sound board side.
+1 here. Put the game in solenoid test. Dose it make the all the correct sounds when solenoids 20-25 fire? If not, try to reseat the ribbon cable. Could just be a crappy connector on the MPU or Sound board.