Gaming DSi won't start up,need help

[Str1der]

Hi,I fixed some NDS Lites before and this is the first time I opened DSi and can't fix it.

The problem is that when it turns on,both screen flashes and also blue light,then it quickly shuts off.
First thing is of course-checking fuses. Both of them are ok.
DSi is charging battery,on Multimeter it's says 4.15V (when fully charged),but I can't check mAh. I guess if battery is charging,then it's not the problem in battery. I tried turning on DSi with 2 different chargers with no luck.

I spent hours on google and youtube,a lot of people are saying to check all connections. I reconnected all of them 3 times,and no luck. Some people said that it needs a new upper screen,but if it lights I guess the screen is ok. (?) Usually when screen is disconnected on NDS Lite,the other one flashes. So I tried to disconnect upper screen,and the lower flashed as expected.

I don't have SD card in DSi,I guess it doesn't need it like in 3DS.
What else can I do/check?
Thanks.

 

[zeello]

Just for the record, the DSi had the problem BEFORE you took it apart?

Do you happen to know when the system stopped working, or what happened to it? (e.g. fell on the floor, fell in water, etc)

 

[Str1der]

Yes,it had a problem before I took it apart.

I don't know the details,but I don't see any sign that it was in the water. Don't know about falling on the floor,there are no traces.
Replacing the motherboard is expensive and there is no guarantee that it will work. If I don't find the solution,I guess I can keep it for spare parts,or to combine with another DSi if/when I get another broken one.

Got some ideas?

 

[zeello]

No idea. :<