Hey DJC, Sounds like dead memory battery. It probably has the original battery which are all pretty much dead these days. Easy fix see attached pdf. The battery holders are pretty easy to find and take a CR2032 button battery (3v lithium), just need to make sure the solder pins of the holder line up with the PCB. There's also quite a few posts about it, search for battery mod. The mouser part number is 534-104 for the battery clip or MJMP can sell you one (that I know will fit correctly).
And you also may need a v2.01 EPROM. MJMP has these. Although IIRC (MJMP correct me here if I'm wrong) the difference between v2.00 (which you have) and v2.01 was additional factory presets and v2.00 added the midi-sysex dump/save load preset capabilities.
Hey that's fantastic that it sounds good
. All MP-1s need a new memory battery these days, the original battery lasted about 18 years, way past what ADA recommended in the manual.