I have a Kawai CP136. This doesnt have protection earth. It has a protection isolated transformer inside. Protection isolation means, there are very thick isolated layers between the power windings and between the internal low-voltage windings.
With such a device there is no possibilty to get a schock, when there is nothing dangerously damaged. Possible Damages can be: Maybe a wire inside got squeezed and got contact with other metal parts. (Just for example) However it must be said, that all wires that have dangerous voltages are double isolated and separated from the other wires. Also the are very short they go directly to the mains switch and to the transformer. All other parts of the piano have no dangerous voltages, especially all outside connectors including USB are low-voltage and secure.
I had my CP136 open and looked inside and I can say this has absolute reliable, fine and solid build quality. So I dont believe, that something is defective.
But to be sure consult a qualified person to check it, maybe measure the insulation or check the connections inside.
BTW, if you where connected to another device or maybe the USB cable was connected to a computer or maybe you where statically charged, I would look for the problem there first. Especially computer power supplies are quite often of poor build quality.
Remark: I am professionaly qualified, therfore I know this.
However, each country might have other power supplys and other voltages. Each country might have other standard procedures which are obligatory to check security. There is special equipment to check isolation and any device is build in a way that it will survive this check, if not defective, and so every qualified person in your country can check it.
Last edited by hpeterh; 03/28/10 02:10 PM.