It's a story about a mains tester screw driver. The screw driver in question had been dropped on to a hard floor from the top of a step ladder, so the little neon lamp inside died when the fall broke its glass shell. Everybody say Awww !!! But hope was at hand. Yeepee!!! A local supplier could make the screw driver work again by putting a new neon lamp inside it. Yeah !!!!
But the screw drivers owner was a cruel fellow, and told the supplier that he wanted to fit the new neon lamp himself. Boooo !!!! So the supplier didn't want to argue with this cruel man, and handed over the new neon lamp with much haste.
Now, the story takes a lighter twist here, because the mains tester screw driver had an all-in-one neon lamp and resistor unit inside when it was new and shiny and working, the new neon lamp only came by itself without the resistor. The cruel screw driver owner didn't care, he just wanted his screw driver working again, so he could jam it in things to see if it made the neon lamp light up. He was a vicious man indeed.
The new neon lamp was installed in the handle of the poor screw driver. The metal cap was hammered back into the top of the handle. The screw driver was all back together and ready for its first live test. You have to remember that the new neon lamp didn't have a resistor supplied with it. The scene was set, the drums rolled gently in the background.
The screw driver was presented to the live mains electricity for the first time with its new neon lamp installed and................BLAM !!!! The cruel owner was flung off the top of the step ladder on to his back. The screw driver had got its revenge on its cruel owner at last.
The moral of the story is "Make sure you understand how things work, before you go trying to repair them".