From time to time the IT Support Unit will issue precall check lists which are intended to help screen out common simple problems. Below is the first. All of the instances have happened. In busy labs with many items of electrical equipment it is surprisingly easy to end up with computers not connected to the mains, particularly if other people are plugging and unplugging things while you are out.
Most labs have local safety trips or fuses.
Check other electrical equipment in the lab connected to sockets close by. In one case a trip switch was physically knocked into the off position by someone shoving filing boxes about. If there is an electrical problem the building superintendent should be informed. Sometimes these leads gradually work their way loose particularly if the machine gets moved about on the bench. Yes, it sounds silly but it has happened.