I recently was trying to fix my new 3ds xl top screen because the ribbon cable broke. When I Finished replacing it, I put it back together and turned it on. It showed the blue power status light, and then shut off, and made the speakers pop. Not sure what I did wrong. I do know that there is one ribbon cable that broke. It went to either the lower screen touch sensor, or the nfc (amiibo) reader. Does anyone know how to fix this?
I recently had the same issue, however I knew what I did wrong since I was able to trace what I did. On the motherboard, there are tabs to flip up for ribbon cables and others that you simply slide the ribbon cable out. If you accidently pulled up on one of those slide connectors like I did, there won’t be a good connection and the 3DS won’t POST. I’d recommend carefully looking over the connectors for the ribbon cables to see if there is any that aren’t flush, then you can carefully try to bend them back down to make a decent connection again.
You need to look for a damaged ribbon cable, it could be the screen you replaced or another component. Make sure everything is set up correctly, nothing is missing and you don’t see any tiny teardown.