I just got zapped for the first time unplugging this AC/DC wall adapter.

I disconnected from the wall and got zapped. It seems to keep a charge for 5 seconds, i.e. the connected LED circuit keeps going. Which leads me to believe that there's a capacitor in there? Can this be? Is it normal to get zapped when unplugging such a thing or is that just due to it being a cheap ass device?

@badlogic Yep. Things like old CRT TV sets are even more exciting. The big caps on that store enough energy to do serious damage for quite some time after power off.

@badlogic Practically all AC adapters have components that can store charge for a bit (capacitors, inductors) - depending on its size, quality and intended wattage that can be more stored energy or less, that's absolutely normal. What is not normal is to be zapped by it, it should be safe to touch under any and all circumstances. What exactly could have gone wrong to make it zappy and what exact problems that could lead to I can't say, for that my electronics knowledge is far too rusty.

@badlogic Can you show a picture of the plug? I guess, it’s not grounded (two instead of three lines).

@reklame yeah, not grounded. Euro plug.

@badlogic Zapped on what side? This is quite common to level the phase variation in DC. But should not reach the AC side.

@Hinnerk AC sife (the one that goes into the wall. Didn't even touch the terminals.

@badlogic you must have touched something conductive though - unless it was an electrostatic zap like you get from door handles (or rather they get from you :)
more important than why is how much, i.e., if it is safe and for that one would need to measure quite a bit. if you get your hands on an oscilloscope... till then i'd assume it's save (because of the output power of the thing) and still try avoiding touching the terminals shortly after shutting it off/unplugging (unless you enjoy it ;).

@etchedpixels @badlogic There should be resistors across the capacitors so that electronics is not dangerous hours after powerdown, no?

@pavel @etchedpixels Happened right when I unplugged it from the wall.

@pavel @badlogic There should. You obviously don't assume that though as it's not 100% reliably true with old kit and in theory they can fail.

@pavel @badlogic @etchedpixels
Ha! No, you can't just add resistors across every capacitor and expect the circuitry to work. High quality capacitors have less leakage, not more.

The second anode of a CRT (where the high voltage connects) and the shielding coating on the outside form a very high quality capacitor, themselves. I once got zapped by a CRT that had been disconnected and sitting on the bench for a week.

@badlogic @etchedpixels And I'd hazard a guess that shock you got was nowhere near the dangerous range. I can feel USB supplies leaking currents through me. I got shocks from electric fence, and they can feel nasty... and yes you should stay away from CRTs, but home electronics should not really be trying to hurt you.