This seems to be getting all too common.

Typical "wall wart" power supply, the LV cord had become damaged where it exits the grommet, resulting in a short. There is no fusing on either side of the transformer, not even an overtemperature cut-out on the primary.

In this particular case the primary burned open circuit before any more damage could be done, but the xfmr was very hot.

This particular unit was plugged into a power strip and thus had 13A protection at least, but this type of poorly designed unit could just as easily be plugged directly into an outlet on a ring circuit protected at 32 amps.

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