Abstract: An accurate, setting-protected, temperature controlled soldering iron has a control circuit including a non-adjustable replaceable resistor mounted near the junction of the handle and the tube which holds the soldering tip. When it is desired to change the temperature of the soldering tip, the handle must be disassembled from the tube to replace the non-adjustable resistor. Very accurate control of temperature at the soldering tip is maintained by the utilization of different laser trimmed resistors having extremely accurate resistances. A window is provided in the soldering handle to observe a number associated with the value of the non-adjustable replaceable resistor.