Galaxy S3: Isn't Getting Power It Seems

[rasmusuperfan]

I've the S3 for a little more than a year, all of a sudden it shut off and wont power back on or even charge. I bought a new battery, tried different cables, and took the phone apart to see if anything looked bad and I didn't notice anything. When I press the power button it will say Samsung, then die or sometimes make it to the Galaxy SIII screen and then die. If I reseat the battery it will try and turn on but die after one of those screens. Similarly, if i push the battery with my fingers it will try and turn on but die first. It won't charge, the LED came on in the beginning but now has stopped. I've seen people with a similar problem but not a solution. Do I need to replace the mainboard, or is that even possible? Any help would be greatly appreciated, thanks