If, starting your NOE GEO model MVS, this error appears:
it does not mathematically mean that the Z80 chip is broken but its communication with other chips could be damaged. In any case, if you have an old Texas Instruments calculator or an old Game Gear or another old electronic device equipped with Z80 (or if you buy it for a few dollars on Aliexpress or on ebay with the component name of 84C00AM!), You can try to replace it (in the picture the original MVS and the one taken from a Game Gear):
If you are lucky and the problem was really in the Z80 and do not insert any cartridges you will no longer get the error but the normal white grid screen of the MVS BIOS: