Thank you Shutterfinger,
maybe it is a switch problem, but. as I said, I have to keep on inserting the battery to make it work, but when I insert the battery back while the switch is off the unit doesn't work. When I insert the battery back while the switch is on the unit works. So it means that the switch still affects the unit.
very interesting the link you posted, sorry I cannot read Japanese, but I with some automatic translator and those really good images I could get through.