My iPad mini screen broke. I ordered a replacement and installed it. But then the LCD wouldn't turn on. I know the iPad is on because when I plug it in to the charger, I hear the sound. I also hear the screen unlock when I slide the screen. But the lcd is black/off. I tried ordering a new lcd but when I installed the new one, it still won't turn on. The charger still makes noise when I plug it but the new screen still won't turn on. Please advise. Thanks.