You can't turn in your hacked n3DSXL to Nintendo in case they find out and deny the repair warranty. Also, you can't uninstall your custom firmware in its current condition because of the instant shutoff. You might have the skill set to replace the speaker, camera, or top lcd assembly that's causing the popping noise but rather not risk doing it yourself nor willing to pay out your own pocket. What to do?
I hope you employ a better variation of this method that I'm presenting because it's an very evil thing to do. If your morals are extremely flexible and your handwork is flawless where no one is the wiser.
The Shameful Guide in uninstalling custom firmware on a nonbootable n3DSXL by temporary borrowing another n3DSXL from Target or Walmart because you don't want to lose out on money and Nintendo Warranty hasn't expired yet.
1. Go to Target or Walmart and buy a n3DSXL Galaxy Edition with cash only at the next town over with sunglasses, hoodie, and deadpan facial expression. You do not want your identity tied to your purchase. Avoid directly touching the n3DSXL cardboard packaging with your hands. Use the shopping bag as barrier or wear mittens.
2. When you go back home, unpackage the newly bought n3DSXL as meticulous as possible. Wear thin latex or rubber gloves to avoid leaving behind smudges and finger prints. Disassemble both your main and temporary n3DSXL.
3. Swap the two motherboards. With your n3DSXL mobo in the 2nd n3DSXL body, backup all your saves and extdata with Checkpoint or JKSM and all your games / DLCs / updates with GodMode9. Also backup your SysNAND image with GodMode9.
4. After everything has been backed up, uninstall your custom firmware and do a System Memory Format.
5. Swap back your main n3DSXL motherboard back to its body and do the same for the temporary n3DSXL.
6. Ensure the second n3DSXL functions correctly. Repackage that n3DSXL in a untraceable like-new condition, just like you received it. Return the n3DSXL at a different store branch at the opposition direction where you bought yours from. Continue the facade of sunglasses, hoodie, mittens, and seriousness.
7. Send your n3DSXL over to Nintendo for repair work.
8. Go to a church, synagogue, mosque, or the next closest religious affiliation you believe in. Pray and confess your sin that you committed. If you're not particularly religious or at all, look up at the sky and shout to the universe that you're sorry for what you did.
9. I don't know, I guess stop feeling bad? An yes, go back to playing your fixed n3DSXL when it comes back.
