Solid blue light, black screen, no backlight. Completely stumped.

I bought a defective New 3DS thinking it would be a fun puzzle to try to fix. I bought it with the description of “black screen blue light.” When I first booted it, I got a black top screen, but surprisingly, the bottom screen turned on—only the LCD displayed pale and almost green hued, with a damaged patch.

That told me a few things. First, it wasn’t a soft brick. Second, the motherboard was operational. Third, the bottom screen was damaged. I popped it open to take a look and to my dismay discovered missing screws, which was just a bad sign. The bottom LCD frame was also broken, so that confirmed drop damage. One top screen ribbon was also inserted upside down, so I assumed that was the top screen issue. Some of the board modules were pried up and a touch loose as a result, which still concerns me.

I reseated the ribbons and turned it back on. Blue light, but no more bottom screen display. Since then, I haven’t been able to replicate that.

I ordered a replacement bottom screen (including frame, NFC reader, digitizer, LCD), quite convinced that would solve the problem. It hasn’t.

I get a solid blue light and black screens. No backlight, we’re talking total black. It stays on as long as I let it, I have to hold power for over ten seconds to turn it off. I’ve tried reseating the wifi card a dozen times and booting with and without the sd card.

I’ve got a top screen replacement on the way, but I’d strongly prefer not to crack open the top half without being certain it’s my last option. The SD card shows no signs of CFW install. I’m stuck. Please let me know if you have advanced suggestions. Thank you!!

Update: After reorienting the top screen underside ribbon cable to ensure it was correctly installed, it now won’t turn on at all. Completely unresponsive, even to charging. Now I’m wondering if the power source was already an issue to begin with or if I somehow damaged the power connector.

Update II: After some diagnostics with functional parts, I’ve discovered the lack of power is due to a bad battery board. Not surprised as the cable shows wear. If I replace both the battery board and the motherboard, I get blue light, popping sound, then off. If I replace just the battery board, I get the persistent original problem of blue light black screen. This leaves me pretty confident that I have a bad motherboard, bad battery board, and bad top screen (I'm speculating that's the source of the pop). I think I need to give this one up for dead.