The 68k didn't receive a reply to command $01 from the Z80 in time. The Z80 doesn't test the SM1 ROM, its RAM nor the YM2610 but if any of those components are bad, they can prevent the Z80 from being able to reply which will then cause the error.
- Check Z80 power, reset and clock signals
- Check Z80 work RAM
- Check NEO-D0 Z80 control lines
- Check Z80 data bus at NEO-C1
Note: Replacement SMT Z80s can be found in some Ti calculators :)
The MV1C board displays this error with no cart inserted since it has no SM1 ROM. This is normal.