Just finished putting an iPad 2 back together after replacing the digitizer and the lcd would not turn on. Plugged headphones in and pressed play button and music came on...CRAP the iPad has battery the lcd isn't working and customer will be here soon to pick it up. Not looking good. Carefully took digitizer back off, reseated lcd, still nothing. found this forum, updated iOS. LCD light turns on, put everything back together and now it's good. ALHUMDULILLAH!
I have repaired several iPad 2 and 3 digitizers and never had this happen. I have been in the habit of leaving the device on so that I could check the lcd to make sure I don't burn it when melting the digitizer glue... Looks like I'll just turn it off from the start next time.
Thanks for the help people. :)