I used to be an RMA clerk for a local computer company. Basically, my job involved testing all the hardware that was brought in because it was bad, and send it back to our suppliers. Pretty simple, bland job, but, I learned allot about computers.
A customer comes in one day with a "dead power supply" (PSU). All the SC said was, "It won't turn on no more". No problem, it happens, probably got zapped by lightning or something. The floor person takes the power supply and hands it to me to test, that is when the following happens:
I take said power supply, set it on the L-shaped counter with the rear fans pointing towards me, which happens to also be the floor persons back. The two of them continue talking while I grabbed the PSU tester and plugged it in.
The wonderful thing about this particular test is, when you plug it into the PSU, it closes a loop that allows the PSU to turn on, and it shows a green light if it is supplying power properly. The bad part about these testers is, if a capacitor has blown, it can smell pretty bad, depending on how bad it blew. After a while, you kinda just get used to the smell...
THIS TIME however, that's not what had happened at all... When I juiced up the PSU with the tester in it, a few feet of sparks and flames shot out of the back of it!!! Which, in turn burnt my arm, and set my sales floor persons shirt on fire. Needless to say, neither of us stood still very long. I ran out the front door with the PSU that is at this point on fire, and my co-worker runs to the bathroom to put his shirt out. Things finally settle a little bit, I get my burn taken care of (very very minor burn btw), and my co-worker strips his work shirt off, and just wears the t-shirt he had on under it.
It's what happened next that really blew my mind though... The customer looks at us and says "YEAH!!!!
what happened when I plugged it in!!!!"
I have never come so close to physically removing someone from my store as I did at that very moment. Common sense would say, if something CATCHES FIRE, you tell the person that is about to test that piece of equipment... I guess that's too much to ask these days though...