jobo multitronic 6220 defect? i´m going nuts...

Hi, I just purchased my first darkroom meter from ebay, a jobo multitronic 6220. I wanted to calibrate it, but everytime i want to measure, it just says "EEE" in the display. is the dam thing defect? or am i doing something wrong? i tried different negatives, different programs, tried to measure in the dark/ light parts of it, everytime the same, "EEE". i´m going crazy. any help appreciated.

thanks,
hans hochstöger