other than trying random things like "0000" "1111" "1234" there was no default code... JVL had no code originally so someone put one on there.
you'll have to reset the system to clear out the code...as it's stored in the IO board. you'll have to remove the battery on it to clear the memory in it (difficult in this machine, as it's soldered in place.)... then boot it up and reset or reinstall the software to original state to totally clear it out and start fresh.
there is a good chance your IO board is going to need the battery replaced anyway... now is a good time to do it.
that said, if someone who owned this machine had megatouch machines too, they may have reused the code from that to keep them the same...the code for those is "4123" and older ones "4777"
if you do manage to get in, you can clear out the code, or change it to something you will remeber.