Chosen Solution
Hello I recently repaired an iPhone 3GS. When I had connected the last of the ribbon cables, i turned the phone on. It worked, but it was extremely dim (practically black). I managed to make it to settings and adjust the brightness, but neither sliding it all the way up or all the way down had any effect. Then, when i disconnected the display and tried to connect it again, nothing was displayed at all! What could this be? I was replacing both the LCD and the glass.
It sounds to me like a backlight issue. What were you originally repairing on it? First, double-check the connectors. Then, I would replace the Display first. If this does not fix the problem, signs point to the logic board, unfortunately.
it could be a bad lcd chip on the logic board. it happens a lot with liquid damaged phones. if a new lcd does not work then i would believe the chip would need to be replaced. no guarantee. it’s extremely difficult to solder something that small, but we’re champs at it here.
I think you can check the 6R8 coil,most of the backlight issue was caused by this item
Same issue I got.Only difference is My LCD is still working with only exception of very dim screen. Any fix to this issue? Please let us know if you got it fixed.
