I see crap like that all the time. I spotted a 12 V circuit diagram once designed by some highly educated genius to indicate when a fuse was blown. Must've been fifteen components in it to sense when the current was flowing through the fuse and when not, in which case it would light a warning LED. Even had a multivibrator in it set up as a flip-flop, feeding to yet another transistor to turn on the LED.
Geeze.
All you really have to do is put an LED* across the fuse with a limiting resistor. Two components.
Two.
Count 'em.
Two (2).
Works great.
Terry, 230RN
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* For higher voltages, a neon bulb with a limiting resistor. When the fuse is OK it has essentially zero resistance, which means no voltage is developed across it when the appliance is on. When the fuse blows, its resistance goes to essentially infinity, which means the full supply voltage appears across it. So the LED (or neon bulb) across it lights.