Thanks for the information ! In fact, I already done this, is you look at the whole CPU board image above, you will see an empty place at the center : the PCB mounted NiCad battery was here. As it was dead when I got the processor, I unsoldered it and replaced it with a wireless home phone battery, of the same voltage, but with a different form factor, so I sticked it on the PCB other side.
Originally Posted by krifartida
Maybe it was a part of the problem anyway : the old battery leaked, and tracks and components pins around was obviously corroded. I thorougly cleaned the corroded areas and re-soldered some points.
For the moment, changing the NE556 eases the things well : the Jobo is up and running again. However, because it's a random problem, I am not sure to have completely solved it.
Thanks again for your help,