My plotters were taking ages to find a fix and I found out the 120 has a lithium battery to maintain a memory.
Many posts suggest the battery,being soldered in, is difficult to replace.
It is but it can be done.
Holding the battery firmly to protect the connections, I gently prised the battery away from the clips using a stanley knife.
The soldered joints are only " tacked " lightly on so come away with gentle persuasion.
To mount the new battery I taped it in place and then inserted a slice of rubber from an eraser above and below to hold it firmly in place.
It means that should I need to replace it again it will be easy.
I should have taken photos to illustrate it but the word is patience and a gentle but firm touch.
