Using a incandescent lamp as a short circuit detector

When powering on old gear or some piece of equipment, which condition is unknown, it's recommended that you either power it up via a variac or use some sort of current limiter and short circuit indicator. So you don't destroy something that otherwise would've been fine.

Now, variacs tend to be expensive and big and specialized current limiters with a indicator light might be cheaper but you still need to spend a higher amount of money. 

The simplest and cheapest variant is simple putting a incandescent light bulb in series with the device you want to test. By choosing the right wattage of the bulb, you can see by how much it is lit up, if there is a short circuit or a excessive current draw or everything is fine. 
I build myself a small box with a E27 socket and the necessary cables, so I can plug the "tester" between the power outlet and the device under test. The more power the device consumes the higher wattage the bulb should have, so that you can draw accurate conclusions from the emitted light. I don't know if it also works with halogen light bulbs or led.

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