Chosen Solution
I’ve got a switch that wasn’t reading game cards. I tested it with a replacement slot from a different switch, and that seemed to fix the problem, so I ordered a replacement slot online. After putting in the new cartridge slot, the switch has stopped displaying anything on the screen. I tried switching back to the old cartridge slot, but there still isn’t any picture. The screen doesn’t even light up at all to indicate that the system is on, but there’s still sound. I can get an image on the TV when I run it docked. The console was sitting untouched between the initial test and putting in the new cartridge slot.
Check the ribbon cables haven’t been caught whilst you were working on it. There’s a small narrow ribbon below the card reader that can cause a black screen if not seated properly.
