The MicroAire radios have an internal "pico" fuse that protects the
unit from reversed power. Ask me how I know ;-) Maybe the Becker has
the same thing.

A pico fuse is about the side of a 1/8w resistor (grain of rice) and
is soldered inside the unit. It is not considered user repairable/
replaceable. While I have been able to replace the fuse, it isn't a
task for the uninitiated without a good small wattage, small grounded
tip, soldering iron. Too much heat and you can lift a trace or scorch
the board. Too big of a soldering iron tip and you might unsolder
more than you intend. A bit of a static spark and the device goes
poof. Sorry to scare anyone but you don't want to toast a very nice
radio.