Chosen Solution
I installed a donor board. When I plug the power in with a battery installed the amber light illuminates. I press power and the blue light comes on and the 3DS boots up. If I remove the power plug when it is booted up it immediately turns off. If I have the battery in and no power cable it will not turn on. I confirmed the battery is 100% in working order with my other 3DS XL.
piechart you have to check the battery connector and check the components around the battery. Use a multimeter for that. Check for missing or damaged looking component. This is a battery circuit issue, which could include a failed power management IC.
