Help! What has happened to my Yamaha Clavinova CLP 411? No sound.

Last year I bought a used Clavinova CLP 411 electric piano. It worked perfectly until last month. For some reason, it started making a loud constant noise which resembled thunder! I could still play, but I couldn't hear the notes very well. When I plugged in headphones, the sound went away, but I could occasionally hear a strange hissing sound and sometimes the notes would not play for half a second.

Yesterday, the piano completely broke down. When I turned it on, none of the notes played a sound and there was absolutely no sound, not even the thunder. When I pressed any button on the piano, every single light on it lit up, no matter which button it was. None of the keys or buttons functioned, the buttons just lit up the piano and the keys did nothing.

So, what is wrong with my piano? What component of it is to blame? I tried buying a few new things and replacing them, but the problem stayed the same. Is it time to buy a new piano?