If your device does not turn off by pressing the power button, that means your internal circuitry are bad. You can easily replace the parts by purchasing one of our repair kits.
In order to get the beeping to stop, you should unscrew the 15 to 20 screws on the bottom of the device and located the battery. Then disconnect the battery at its plug.
For a problem like this, you shouldn't just change the mainboard. A bad mainboard can lead to a bad sensor board, and bad bluetooth module (if yours has bluetooth). So you should always change these parts together by purchasing our Hoverboard Repair Kit.
If you don't know which repair kit to get, feel free to email us a picture of the insides of your device at email@example.com so we can direct you to the right kit and a step by step repair video to help you fix your hoverboard.