After picking up an original brick-style GameBoy DMG-01 recently to install a backlight, I found that the screen was plagued with missing pixels, forming vertical lines of missing pixels. This tends to be on the edges of the screen, but can be anywhere on the screen. Adjust the contrast dial so that the screen is very dark, making it easier to see where the gaps are.
It’s actually quite an easy fix. Start by removing the rubber strip across the bottom of the screen.
And then, with the console switched on, press your finger down on the plastic strip that is joined to the glass, you’ll notice the missing lines probably start to fill in. Now you may be able to fix it with a hair dryer and applying pressure, but I didn’t want to risk breaking another hair dryer!
So instead, I chose to use a soldering iron, with it heated up, rub it across and up and down under where the missing lines are. Gradually you’ll see them re-appear, take the iron off and wait for the plastic and the contacts under the plastic to cool down.
Keep doing this for the affected areas and eventually you’ll end up with a fully working screen again.
Don’t forget to replace the rubber strip, it will help keep a good contact. You may find that you have to put some new double-sided sticky tape on it to hold it back into place.
As with everything on this and other modding sites, you do this at your own risk! The plastic sheet and contacts that you are heating up seem to withstand having a soldering iron applied to them very well when I tried this, and I’ve done this to 3 consoles now without damaging them. It’s probably a good idea to keep the iron moving, I imagine if you just held it in one place for too long then you could damage the plastic sheet/contact.
This info is taken from various YouTube videos.