Fiddling with the contrast sometimes works for me with horizontal lines. I tried capturing it but of course there was one line that just wouldn't quit.

For missing columns, I can vouch for this method being at least a temporary fix.

If you have horizontal columns, then you have twisted the fabric of space/time so badly that it may be too late for us all.

To my my knowledge man theres no known "easy fix" I've been told it can be fixed "sometimes" but it's hard and very tedious apparently. I've tried a few and had one work but I did it with a very lucky piece of tape. If you can turn the gameboy on while it's apart and see your lines and mess with the ribbon ok the side and notice them fix try to get a piece of tape to hold them together. Maybe it'll work but dot count on it.

I know this thread is practically dead, but what if you have horizontal dead columns? Is it too late for my DMG?

First google image result for "game boy dead columns fix"

You have to remove a black piece of rubber, it heats up the glue there and reattaches the connections

Ok, just making sure.

I'm pretty sure he means the ribbon cables running out of the screen.

You mean the ribbon cable that connects the PCBs?

Make sure the game boy is on, then run a soldering iron around the ribbon cable at the bottom until you notice the columns have returned.

My gameboy (DMG-01) has a lot of dead columns. Any way to get rid of those?
I see a lot of posts about dead rows, but I've been told that's a completely different problem.