Chosen Solution
Replaced the screen/frame on an AT&T S20 Plus, transferred over all parts including front camera, charging daughterboard, 5G antennas, etc. After sealing it back up, it’s not detecting the cellular network. Fearing a bad part, I put it back in the original screen/frame and same thing. All connectors look fine, pressure pins on the charging port are in good condition, too. Anyone have any ideas? Thanks in advance!
I know on a S21 Ultra, I did a screen assembly swap and the part was identical but once I powered it up I had the same issue. Not a single answer made sense. Finally someone mentioned replacing the screen assembly fixed there’s. I dug deep into the screen assembly and learned there is a small antenna flex on the corner and it’s held down by tri-wing screws. It turns out they aren’t universal. The “international” assembly uses a different band antenna. So I swapped my original flex and instantly had a signal again but this time it actually worked on the AT&T network. What an ordeal! Maybe the S20 is similar? As it turned out, the SM-G998U uses a different version of this LTE/4G antenna than the screen used on the “B” variant (SM-G998B)
It’s not the 5g slot with 2-Philips screws… it’s pushed up into the frame. I used to have a picture. “Flex” it’s a ribbon with 4-5 attached hold down screw slots it’s L shaped to fit in upper top and right side.
