Let me tell you something. From my experience, your problem had nothing to do with files or system being modded, regarding the screens staying dark. Specially because when u boot system without card it takes you directly to the menu and you can hear your system booting successfully. You probably have the Luma copy to nand and that's why you can boot without microsd. When as you boot with card, what's actually happening is that your getting stuck on Luma first time boot configuration page. Boot with Luma firm in memory card and press start, do you boot successfully to 3ds home screen and can hear the system sounds? If yes here is what I think is the problem: your cameras are bad.
Sound crazy right? But I bought a system of ebay with same exact issues, would boot up, could hear them home screen but both screens were Black. Swap lcd, motherboard and everything except cameras. Same issue nothing change. Swap camera, both screens came up. If u don't mind taking a risk try this: cut the wide black ribbon cable, it's the camera cable, the one that connects at the top right corner on the motherboard, the 3ds needs the cameras to boot, so just disconnecting camera ribbon will cause it to shut off. However, it really just needs the ribbon cable connected to motherboard , what goes bad are the camera chipsets that short the screens on motherboard.
Try at your own risk, but I have fixed many 3ds with this common bizarre issue, it has been the camera everytime. This only applies to system that boot up and you can hear the sounds and menu and button press in system but that have both screens black.
Last edited by Johnnykillertech,
