MC-505: Displaying ROM Version
Use the following procedure to display the ROM version of your MC-505:
1) Turn the unit off and back on again.
2) Press and hold the following buttons and keyboard pads in this order:
TEMPO/MIXER, PTN/SONG, PATCH, keyboard pads #12, #14 and #16.
3) The display will now show the current System version number.
4) Release all buttons and keyboard pads when done.
Note: If the current System version is not displayed, repeat this procedure
beginning with step #1.