I have found a halogen lamp that only works when plugged to the wall socket the right way. I am baffled by this behaviour.
The plug is a Type C plug, no earth connection, just two symmetrical metal rods. The socket is European: AC, 220-240V, 50Hz.
As far as I can understand, it should not matter which way the plug is inserted into the socket.
- If the lamp uses AC, then both rods will be alternating polarisation and both orientations should work exactly the same.
- If the lamp works on DC, it will have some internal rectifier / regulator electronics inside that will transform the AC in DC. These circuits, by design, should work regardless of the orientation of the plug.
What am I missing? Which electronic design may result in a lamp only working if it is plugged in the right orientation and what would be the rationale to add such circuitry to the lamp in the first place?
- Other appliances (such as laptop chargers) seem to work as one would expect in that socket.
- The lamp exhibits the same behaviour in other sockets.