The first thing to check is if there is any corrosion on the MPU from battery leakage. I suspect there will be some as the most affected area is within the reset section of the MPU. If the original NiCad battery is still in the board, then it needs to be cut out and replaced with a battery pack or similar.
The sound option is set via setup #18 and selecting 00, 01 or 02. If you are resetting the MPU via the reset switch on the MPU then this setting will not be retained. Also, if the battery is flat, then it will lose this setting also.
The easiest test is to remove all the connectors to the MPU board except J4. Then switch on the game and look for 7 flashes. You can clean J4 connector pins and gently reseat the socketed chips. Be careful that you do not touch U8 (5101) as it is a CMOS device.
