I bump this thread, I have a similar issue, no sound with unibios and eroor with OEM BIOS on MV2F
Z80 changed no difference.
Then I found that "start P1" didn't worked to make appear the test menu (but the Start button was OK on NEO-C1 pin).
So I changed the Neo-C1 as it manage also the SDdata.
Changed it, then menu now works, colors bars, RTC, inputs, memory detection, DIP switches all ok, but...sound still nok.
I will check the SM1 Rom and eventually flash a new one. The only thing I suspect again is either faulty Neo-D0 or still faulty NEO-C1, I dont see SDW changing but perhaps it's normal.