Quoted from KenH:There are not a lot of posts about that IC and nothing about the volume changing between power ups. It is the only thing I can think of to try to solve the issue.
If the game's screen is reporting that the volumne is at "7" where it was at "10" last time, that's NOT a function of the 9503 - there's no way to 'read' its current value, just set it.
If the game's screen is showing 7 vs 10, then that's an issue in the game's software/MPU/Sound Board processor... The volume level's stored in the game's RAM..