I would start by double checking that you have the tile and sound roms in the correct locations, I recall that the order they were placed in was not intuitive.But, Background and sound is imperfect.
I think changed pinout (like SNES Carts) or protection/encryption in 538100 chips.
Sound (effects) is very regular.
If you have a scope you can check the voltage levels on the ROM control and address lines. TTL voltage for a logic high level is far from 5V. It's likely to be within the tolerance for the flash chip. Check the datasheet.good, I will try and prepare for a conversion of my battle ballz too.. not too keen on using MX29L3211 without proper levertranslation for all affected pins, but I do got a few of them ready to go.. hmm
when you change sound you need to re-transfer to mobo, sound data is saved on mobo, graphics data is streamed from cart.