I purchased a iphone 4 with crack screen. Upon replacing the screen I noticed the battery connector was corroded. I cleaned w alcohol/toothbrush and ordered a new battery. Screen repair was a success. I then replaced device with new battery. The device will only power on only while its plugged into charger. Once unplugged the device will power off. I have changed dock connector and soaked logic board in alcohol for approx 30 min. The device does same. Can any one help???