I think you will find in the older Rolands the service mode was like a "s" shape then a "v" shape. With the main power on but the front pannel power off use the key pad as so: up,left,right,down (like a "s" shape) then left,down,right (like a "v" shape) and then hold down all 3 (left,down,right) together and press power on.
For the newer Rolands it is similar but reversed. up,right,left,down then right,down,left and hold all 3 left,down,right and power on.
Some times it can take a few trys to get the sequence to enter. The CJ 500 arrow pad (bubble like pads) is harder than the FJ 42 which has raised button keys.