On a Bernina, there are two circuit boards. One is the "motherboard' and the other is the "power" board.
When the motherboard goes out, signals get scrambled. When you push a button or select a stitch, it may give you something other than what you selected. Or it may not do anything you select.
When the power board goes out, the machine won't turn on.
In both cases, a component on the circuit board quits working. It could be caused by a power surge. One common problem we've seen with power boards, is that the machine hasn't been used in 6 months to 3 years. There's a component that is supposed to stay charged, but it looses power when the machine isn't turned on and used.