My phone stops turning on (black screen)

@flatisgames since you've stated that "My phone stops turning on " I make the assumption that you are now referring to your phone and not the alarm clock.

Let us know if your phone vibrates when you try to turn it on. If so, it is turning on but you can't see it. This is most commonly a screen issue.

If it doesn't vibrate and shows no sign of life, then the issue is most likely a power related issue. First you want to check your charger. Make sure it supplies the proper voltages. Check to make sure charge cable connectors are not bend etc. After that, check the charging port. Make sure there is no corrosion, debris etc. that prevents it from working. Clean it of any debris etc, use a few puffs of air to clean it out.

If none of this works, get a ammeter and see if your phone draws any amperage from the charger. After that, you need to check and see if your ,ainboard even gets power. For that of course, you need to open it up. Post Some good pictures of what you see. That way we can see what you see Adding images to an existing question. iFixitでの質問に画像を追加する方法

Since iFixit does not yet have a specific guide for that, use something like this video You will need to check the sub_board (charging board) for any damaged components as well as check the flex cable going from the sub_board to the main board., Those cables love to either fear or get disconnected so do a very close checkup.

If none of that works, check the Samsung flowchart for the No Power situation. My prime suspect is the sub-board with the flex cable being a close second :-)

While you work on your phone, take lots of pictures. Once you are done with it, take those pictures and create a guide for iFixit. That will help the next person that has the same problem as you do. It's easy and fun to create these guides. https://ifixit.com/Guide/new The iFixit community will appreciate this.

Repair is War on Entropy!