Nintendo 3ds won’t turn on without popping sound

A few months ago my Nintendo stopped working. It doesn't turn on and makes a popping sound when I try to turn it on. And when I connect the charger it holds the orange light for a couple of seconds and it shuts down. I realized that this could be caused by a speaker or an LCD ribbon cable, so I decided to disassemble the console and fix the damaged part. Finally, I noticed that the speaker ribbon cable was ripped. So I replaced the speaker ribbon cable with a new one but the console still wouldn't turn on. Now it no longer pops when turned on but the behavior is the same.

I also check:

• Try to charge with different AC adapters.
• F1 and F2 fuses are OK.
• Try a different screen and camera.
• The battery seems OK (It gets 4 volts when it is tested with the multimeter).
• Both screens flash white before the console turns off.

What else can I do?

Thanks in advance :)