To keep non-volatile memory alive, your SY99 is equiped with an internal backup battery.

If the Warning Message 'Change internal battery!' appears when turning the SY99 off, call a local Yamaha vendor to replace the battery. It is highly recommended that you store a complete ALL backup on floppy diskette.

The lifetime of the internal backup battery is told to be more or less five years. It is said that the internal battery is being regenerated, when the SY99 is powered on. This would mean, that if you use your SY99 frequently, your battery might have a longer livetime. But maybe it's just the other way round. We are not sure on this.

You can not replace the internal battery on your own. Call Yamaha Corp. for battery replacement.