White apple logo for about 10 secs then dims and never boots

Hi, I've done my reading and am stuck. My iPhone had a broken volume switch and broken home button. I sucessfully replaced both. I should have left it alone. The problem came about because when I replaced the home button my LCD had some visible dirt that bothered me. At this point my phone was fully functional. I simply took it apart to clean the LCD and glass. When I put it back together it quit working. I must have taken it apart 10 times by now and checked everything. I even replaced the battery and got the same results. This is what happens: If you press the power and it's not plugged into ac power nothing happens. If it's plugged in then the apple logo appears for about 10 secs and then thr screen dims and you can see the apple logo faintly and that's it. Connected to the pc nothing happens. I hope someone has some help with this. It's been a long week without a phone. TIA