Keyboard not working

[I'm confused]

Good morning folks, I hope one of you good people can help me. I have Yamaha Keyboard which I was allowing my son to use for school, however last night he plugged the wrong power adapter into the unit and switched it on. The consequence of this action is that when I've connected the correct adapter the small red LED shows that it is powering up although there is no obvious response or sound no coming from the keyboard, it's as if it was dead. Peculiarly, if I remove the adapter and install batteries it works perfectly. I hope someone will kindly advise what the problem may be
Thank you!

[train123]

If it works correctly with the batteries, the majority of the keyboard works. Right after the power adapter socket on the keyboard, there is a voltage regulater that likely is fried. You'll need to have that part replaced or fixed. If you want a low priced solution, you can replace the batteries with the equivelant DC power adapter. AA, C and D batteries are 1.5 volts so multiply by the number of batteries and you'll know which DC adapter you'll need. An example is if 6 batteries are needed x 1.5 volts/battery = 9 Volt DC power adapter is needed.