The red jumper on the back of the CPU board near the edge connector is for the address space. To get this board going, I'd start by burning the missing roms for Nibbler and fixing that jumper on IC6 that has come loose. All the rest of the work looks to have been done for you. If your going to make a Jamma adapter, note that pin 1 on the CPU board is on the right if you are facing the edge connecter. In the Jamma convention, pin 1 is on the left. Don't get that backwards, the 12v and 5v are in mirror positions on the edge.
Nibbler does have a sound rom (IC53) where Vanguard has a SN76477. That sound rom just supplies the coin-up sound effects (7 sounds which rotate until 9 credits, then uses the same sound for additional credits). On Vanguard the extra SN76477 is used for the two phaser sounds (shot A, shot B on the schematics).
IC51 on most Nibbler boards is empty. However if you put a sound rom from Pioneer Balloon or Fantasy (and probably Vanguard) in that socket, you'll hear music in Nibbler for the first 14 waves. Some Nibbler boards in the wild have IC51 from Pioneer Balloon. In MAME, the Nibbler6p rom set includes IC51 from Pioneer Balloon, if you want to try it out.
PS - This thread on my FPGA project for Nibbler/Fantasy/Pioneer Balloon (and Vanguard) talks a lot more about the hardware variations between these games that all the share the same platform: https://forums.arcade-museum.com/showthread.php?t=373372
Nibbler does have a sound rom (IC53) where Vanguard has a SN76477. That sound rom just supplies the coin-up sound effects (7 sounds which rotate until 9 credits, then uses the same sound for additional credits). On Vanguard the extra SN76477 is used for the two phaser sounds (shot A, shot B on the schematics).
IC51 on most Nibbler boards is empty. However if you put a sound rom from Pioneer Balloon or Fantasy (and probably Vanguard) in that socket, you'll hear music in Nibbler for the first 14 waves. Some Nibbler boards in the wild have IC51 from Pioneer Balloon. In MAME, the Nibbler6p rom set includes IC51 from Pioneer Balloon, if you want to try it out.
PS - This thread on my FPGA project for Nibbler/Fantasy/Pioneer Balloon (and Vanguard) talks a lot more about the hardware variations between these games that all the share the same platform: https://forums.arcade-museum.com/showthread.php?t=373372
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