USB soldering iron test and teardown with schematic.

When I bought this I was very sceptical that anything powered from a USB port could actually produce enough heat to solder. But here it is, tested and reverse engineered for your viewing pleasure. Note the warning about using it from plug-in USB chargers. Most ungrounded versions have significant capacitively coupled mains leakage on the output that will be present on the irons tip and could damage some overly sensitive components. In delicate situations it’s best to power the unit from a decent chunky U