My iPad 5 Wi-Fi will not turn on.

Hello all, Similar to other questions but not quite all. My iPad 5th Gen Wi-Fi was working fine all weekend. Had good battery (say ~%50) and just went blank/turned off without notice. Could not turn on. Could not hard stop nor hard start. Tried the Home+Power restart. No joy. Has not turned on since. Took it to the Apple Store they could not connect to the iPad with their jumper~diagnostic plug in handheld. The store rep very kindly looked at me and said he couldn't get past the adapter plug or battery, in short, it was dead. Now it sits on my counter not working. I'd like to try and fix it if I could. Any ideas are appreciated. I am an electronics technician by trade but this one is too deep for me. I've got micro min repair credentials. If I knew where to start I could probably save it. Help me hive mind fixit people, you're my only hope.