His trailer had some twelve-volt circuits that ran off battery power, and these still worked. So he was able to go in and grab his soldering iron. But it required 120 volts AC. Normally this would be supplied by the generator. But the generators were all dead because they were controlled by systems that had microchips in them. For that matter, so did the soldering iron; it had a built-in thermocouple and some logic that varied the power to keep it at a set temperature, turned it off when not in use, and so on.