I am looking for a service manual for the mentioned device. Currently there is no output on the display. I am wondering if there is a backup battery inside that could have leaked but currently i don't have access to the device to check. I know for sure it is a microprocessor based. Makes me wondering what systems were used by Robotron in the late 80's. Any information about the device would be useful, even a user manual. Cheers to all the german engineers here!