New Nintendo 3ds XL -top screen not working, headphone socket works.

I opened up my New Nintendo 3ds XL to apply a few wires to it and there are no shorts to the wire or to the soldering. But when I closed up the Nintendo and tried to switch on, there was a pop sound and the Nintendo switched off in about a 3 seconds, it dint boot to the desktop. But reopened and reseated the cable and the bottom screen is working with touch, and but the upper screen is not. There are no pops now, and the system is booting, only that the upper screen is not working or lighting up. There is sound via the headphone socket but not through the speakers.

How would I repair this. Please could you answer. Thanks in advance.