Well, this is somethig...
It looks like the black line appears depending on the image that has to be displayed.
I made a short video
https://www.youtube.com/watch?v=5q84bVXpFMI
The black line on the right is clearly visible when the column must be white (Nintendo logo, ...). In other images, it displays exactly what it's meant to be displayed (0:12 to 0:25).
I've noticed it during the game, too. It also becomes white with some images...

Not a bad hypotesis. I have to check if the column, when using a game, displays something or remains all black.

First thing to come to mind is years of non-use of that particular line has preserved its sensitivity. Other lines need to be driven harder for similar contrast. No possible fix?

Hi, everyone!

I'm new here.
I revived my old GameBoy to start testing music production with it.
First problem to solve, dead columns (columns that are white with lower contrast).
I've read here and here about how to fix them, and actually "almost" fixed them. I proceeded with the flat cable "ironing", and now there are no more white lines, BUT a line is more black than the others. It is not always black (with max contrast it disappears like the others), but it is easily visible with normal contrast. By ironing the flat cable again, I'm able to let the column disappear and reappear (the normal behavior you get when ironing the cable), but it always reappears too black.

Any idea about how to fix this?
Thanks!
MIX