Galaxy: green lines or a black patch after a drop, or after an update
The glass is intact, but a green line crosses the screen, or a black patch grows day by day. Here is what is happening under the glass.
On an AMOLED screen each pixel emits its own light. When the panel is damaged, the symptoms differ from an LCD's, and they evolve.
The green (or pink) line
A one-pixel-wide vertical line, often green or pink, appearing after a drop, pressure, or sometimes after a system update. A control trace in the panel has failed. It doesn't necessarily get worse, but it won't go away. Only replacing the screen makes it disappear. On some models and periods Samsung has covered this defect; ask them first, and we tell you if that applies.
The spreading black patch
That is organic ink from the OLED panel leaking after a knock. The patch grows within days and touch follows. There you have to act fast: the longer you wait, the more the panel degrades, and dead touch makes the phone unusable, even for a backup.
The repair
In both cases: genuine Samsung screen with frame (service pack), fitted the same day by appointment, data kept. We take the opportunity to check that the frame hasn't suffered and that the battery wasn't pinched by the knock.
A tip: do your Samsung Cloud or Google backup as soon as the patch appears, while touch still responds.
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