You could also just use Google, just saying...
The "popping" noise is a common issue on the complete DS family, it protects the console from damage due to shorts etc. by not letting the console power on if one of the ribbons aren't connected properly or if one of the components are faulty.
The thing that sucks is, that you don't know what isn't working, so you have to take the 3DS apart again, reseat all the ribbon cables and check for rips. If a cable is ripped, that component is toast and you need to buy a new one.
You should also make sure that all the clips on the connectors on the motherboard work and aren't broken. If you broke one of those, you have a few options:
-you can replace the motherboard ($$$)
-you can solder a new connector (difficult)
-you can try to replace just the clip, did that a few times (tedious but worth it)
-put pressure on the connector by using toilet paper, for example, between the cable and the case of the 3ds
If you need more help, feel free to contact me, 3DSs can be very difficult at times because of the hardware check