You’ll need to have some charge in the battery to boot far enough for any troubleshooting. I’ve even had cases where it was difficult to get the battery to charge, as loading the charging screen took too much power to load. In these cases cleaning the USB port and/or using a different charger usually helped.
If you have a universal battery charger you can also try charging the battery in that - it should at least give you an indication of whether the battery still works. Also, note that a common fault in FP1s is a broken USB port - depending on the defect charging may still work (requires two wires) when ADB (four wires) no longer does.
thanks for your reply. After searching for the last 2 hours, i found similar problems. It’s most probably a broken power button which constantly reboots the phone. I managed to enter recovery mode.
When i do the key test, I open the test mode and after 1 second, the “power button” line will disappear, and shortly after that also “volume down” and “volume up”. Is this supposed to happen? I thought that they will only disappear, when I press the buttons?
I didn’t thought that, but I managed to repair it. After entering the recovery and doing some test, I wasn’t able anymore, to access the recovery. After letting it “load” for 1 hour, I managed to enter some other recovery:
Watch the image. First I only entered the right mode, for some reason I was then able to enter the left mode.
There I did a factory reset and the Fairphone works again.