I hope this doesn't happen to me. Lesson learned. As a diver, I used to read all the things that killed people underwater. Now I read about all the people who get killed with electricity. It is dangerous!! Be careful!! I bought a pretty nice kit from Elenco. It is a well known adjustable power supply. Do I need one? No. Did I want to build one for the fun of it? Yes. I am OK at soldering not great. Pretty new. I took my sweet time and soldered it all together and everything looked to be in order. The guys with experience said, "I did it in one afternoon." Took me three days. Again, I took my time. I plugged it in and nothing happened. Fuse I forgot. Put the fuse it and it worked!! It lit up!! I was just getting ready to check the output and got up for a stretch and walked out of the lab. I was in at my kitchen table and heard this, "KaBoom." Oh that did not sound good. I am so glad I didn't have my face down in the power supply looking at it. A capacitor blew. I never did find out why. So of course I did what any science guy would do, I watched capacitors blow up in slow motion on Youtube. I learned something. They are built to blow up slowly. They have an X mark on the top to relieve pressure in case they overheat and then then just fizzle. Well I hate to tell you this but this capacitor did NOT fizzle. It blew up. I found the external casing and it was still totally intact. Still had the FAILED X on top and somehow, some way the capacitor failed to do what is was suppose to do and did not blow up the right way. Instead of a fizzle it was a freaking bomb. It was not like the little explosions I saw on the Youtube videos it was LOUD. I sent the unit back to Elenco, got refund, no questions asked. What caused this? I have no clue. I just can't even believe I would have put the capacitor in backwards. It must have been something else. Never did figure out what caused it. Some newbie bad wiring I guess. In conclusion to this huge tome of a response, I would like to say this. If you build a project using AC current, before you plug it in after the build, put on goggles and ear protection before you do so. Maybe even a bomb protection suit. Or plug it in outdoors and get away from it and watch it. Be very careful. Again, I'm glad my face was not down close to this capacitor when it blew.