Thanks Jim,
I do not have access to a EPROM reader/programmer so far. This EEROM has to be replaced in the powered on instrument as stated in the service manual (first copy the data into RAM, then replace the EEROM, copy the data back to EEROM). This ROM probably also harbours the the device's firmware, so loosing the data would be really annoying. Apparently reading the ROM is OK but not writing . I could not find any circuit drawing of the instrument showing how the EEROM is written. I don't want to harm an instrument with less than 1600 working hours.
Regards Phil FM5GB