Yes, the pi itself powered by a usb power supply is booting and working.
However i will measure the pi 3,3v and 5v gpio-outputs today to ensure the gpio-part of the pi is okay.
I also recognized the opensprinkler-board (WITHOUT the raspberry-pi connected) does NOT output 3,3v on the gpios? (see my screenshot: i mean the pin below of the marked 5v output)
Can anyone confirm that?