Samsung Galaxy Tab charges but wont turn on

Hi, I'm at my wits end trying to get my Samsung Galaxy Tab to work to keep a very sad 9 year old happy on holidays. I've tried all online and Youtube suggestions including power+volume, disconnecting battery etc without luck. The funny thing is it is charging to 100% no problem, but when try to power on it goes black screen and stays there, on one occasion the Samsung logo came up, got excited, but froze and stayed there, can anyone help who had this specific problem, many thanks..