Thank-you for your help Scott Hamlin and CeLviaNo. At least we know how to turn of the Backup now, but it isn't fixing our problem. The G key plays much louder than all the other notes. The touch response for the key isn't working. It sounds terrible. I suppose I will have to contact Casio and see if they can fix it.
Hi, We`re new owners of an AP450 and didn`t think it would be a problem if our little grandkids played it. It looks like they`ve pressed some buttons and now one note is off. It has no touch response. Unplugging doesn't help. The manual suggests turning off backup, but even though we`ve read through the manual a few times, we can`t figure out how to turn off backup. Could someone walk us through it step by step?