Chosen Solution
I’ m troubleshooting an iPhone 6s logic board. It’ s dead but no visible damage. When i power it trough the bettery FPC with a DT880 it draws 100ma even when im not trying to turn it on. When i try to turn it on nothing happens. Edit: It has been water damaged. I cleaned it with isopropyl alcohol a day later. I am testing only the logic board, without other components
This would indicate a short on one of the power rails possibly a sub off VCC_MAIN. You will need some schematics and board view to track it down.
