Usually if the item functions ok for playing but cannot store presets or write patterns or programming es the internal battery is dead. All gear that have RAM will require an internal battery to keep these current. Even your computer has this. To tell if this is REALLY the problem , do this:
1. if with maibs power you cna write or store presets or whatever, but if you turn it off you have lost the,...- your battery is DEAD.
2. if with the mains on you CANNOT write presets then something ELSE is wrong....
These batteries, in my experience, last about 12 years or so for digital gear, but I have had to chnage them. Sometimes the batteries are wierd sizes but you can hard wire often with battery clips and boxes (from SIMLIM) with standard alkaline batteries. Hvaing said that, you can buy whatever battery shape you need in SINGAPORE. Look in the yellow pages. When I lived in Singapore, I found a stockist of all sorts of strange battery sizes in some Bedok Industrial estate.