Bernina Activa 140 loses power

Question

We have had our Bernina 140 for a number of years without any problems until now. While sewing, it loses all power as though it has been unplugged - needle stops, light goes out, etc. I don't think it is overheating because it sometimes does this literally in the first minute of use and other times it does not do it at all the whole time the machine is in use.
Any suggestions?