Starting from a very simple idea, this Blown Fuse Indicator circuit can be a very useful indicator for your electronic workshop.
The simplicity of this circuit using only two components, but although with only a resistor and an LED, this circuit provides a visual indication of when a fuse has blown. LED1 is off by default because the “short-circuit” caused by the fuse, F1.
If the inevitable “big bang” happens in your circuit loads, then LED1 will be turned on, it means that the fuse has broken. Please note that the LED does illumininated under false pretenses, ie with a short circuit or shunt to the load. In this case, the current is reduced to a safe level by R1.
Blown Fuse Indicator circuit source: http://www.zen22142.zen.co.uk/Circuits/Power/fusemon.htm