Power on, Apple logo shows for split second then black screen

I am a cellular repair tech and fix many iPhone and Androids daily. 80% of which are iPhones. But I'd have to say this one has me stumped. I dropped my iPhone and broke the digitizer AND lcd. Upon replacing the battery was completely dead and showed the battery logo with the thunder bolt indicating it needed to be charged. The battery logo stayed diplayed the entire time it was charging until it had enough charge to boot up. While booting up the Apple logo appeared for a split second then the screen went black. The phone itself continued to boot up. I can connect to iTunes, play music on my phone, receive calls/texts, answer calls (sliding my finger across where the bar to answer is), but no display at all. I have tried multiple hard resets, factory restores, tampered with the connections while the phone is on, examined the entire logic board and connectors and nothing seems out of place. I have never had an iPhone with this issue. Any suggestions or solutions would be greatly appreciated!