Weller W101, 100W Temperature Controlled Mains Soldering Iron - Weller T0056104399N, The Weller W 101 is a 230V AC mains voltage, temperature-controlled soldering iron with an output of 100W, making it suitable for medium and heavy electrical connections to transistors, PCBs, heavy-duty connectors and sheet metal.The temperature of the iron is controlled by a built-in 'Magnastat' thermostatic switch. As magnets are heated, their strength reduces and this principle is used to operate a spring-loaded switch, turning off the power when a certain temperature is reached and turning it back on when the iron cools down. A click can often be heard or felt when the switch operates.The operating temperature of the iron can be changed by swapping the soldering tip. Each tip has a disc fitted to its end which touches the thermostatic switch inside the iron. Different tips have different discs to which the magnet is attracted by different amounts, changing the temperature at which the thermostat sw