I would try cleaning any corrosion from the connectors and any where else it's evident on the hardware especially metal connections if that doesn't help then look into changing parts

I'm not really sure what the grounding would be if anything it's on that smaller board and it's gold strips touching other gold coils to be honest though it sounds more like a bad replacement part was your screen doing that before replacement? If the connections weren't proper I'm not sure the screen would display anything but for good measure clean all metal on metal connections and avoid touching them with your bare hands make sure all connectors are in their place and secure do a power on test before reassembling

ZEOSAGECARNEY read my last post for some reason it posted it above yours about giving it a charge

I'd just let it charge for a solid 8 hours if it's a new battery it most likely didn't have much of a charge when it left the factory if any so give it a good charge and post back if nothing changes worst case scenario it's a short on the main board

I'm really not sure if you say the flex was tested and working on another phone then it can't be the part and you say the connection isn't loose when reinstalling it the only thing I can think of is one of the pins in the connecter on the logic board and/or on the flex was broken I doubt you could find the replacement for the logic board but look really close maybe take some pics with a really camera and make sure none of those pins are bent or broken.

@blackstar & WellTrainedVC no problem guys glad to help

@Howard Lin I used a #00 screw driver it's pretty small but there are smaller size

@Kyle Shaw your welcome man glad to help

Reinstall the display software? What service center the carrier or manufacture ? Did you need a new screen or was there another problem or reason for leaving your phone with whoever?

Thanks walter i know the pics are bad i didnt really look at them until after i had my g2 back together and like i said i used my sisters S3 camera not a high powered nikon or anything like the ifixit techs use.

@chris i didnt have my micrometer handy to gwt a good measurmwnt of te screws but all of them are the same size except that black one i mentioned in the guide hope that helps

I apologize about the bad pics and vague decriptions i should have labeled it a disassembly ,but it was tue middle of the night i wad bored and ifixit didnt have a guide at all but questions about a few things so i used my personal phone to make this . If anyone wants to make a better one feel free and ill tell the ifixit team to take this one down to anyone this guide has helped glad it did your welcome