I'm fairly sure that most, if not all, System 11 games that have the D-11581 sound board (or variant) provide a "bong" at boot. That "bong" comes from the sound board. So, no bong, sound board issue.
I recommend getting the battery holder off of that board ASAP. System 11 boards are tough to replace and ALL batteries leak.
If you want to send both boards to me along with the ribbon, I can repair whatever is not working, and install NVRAM on the MPU for you. Drop me a PM if that works for you.
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Chris Hibler - CARGPB #31
http://www.ChrisHiblerPinball.com/Contact
http://www.PinWiki.com - The Place to go for Pinball Repair Info