Well that was interesting. Just tried to plug in a switch-mode power brick for a laptop and was greeted with a 1″ diameter bright white flash burst out of the outlet.
Now part of the adaper prong is singed off. Given that the formerly white power adapter casing around the plug connection now has a shiny metallic layer on it, presumably the tip was vaporized and the metal was ejected out of the outlet and then covered the adapter.
These switch-mode adapters almost always create a small arc when I plug them in but not ever like this (I own 3). Nothing was attached to the power supply when I plugged it in. I presume there must be an internal short. I will take it to the Apple store as a memento for their engineering team.
As for the house, everything is fine. The circuit breaker tripped, no fire ensued, and I got off with a scare. Should I have the power outlet replaced though? It’s a beefy commercial-spec 20A unit and still seems to work fine (other appliances work well inside it). Yet, I remain suspicious. Any thoughts would be appreciated.
Replies
Basically those consists of diode bridge that feeds in to a big capacitor. It will generate about 170 volts with a very high ripple.
Then a switching power supply with a small transformer will convert it to low voltage. Then it is recitiied to DC and a small filter. Feed back from the output is used to control the switching power supply and thus regulate out the ripple from the filter and changes in power voltage. That is why some thing are rated for 100-250 volts without any changes.
The switching power supply typically runs at 5-100 KHz. That is why the transformer and the low voltage filter can be very small.
The big line capacitor is why they arc when first plugged in. It take a large surge in current until it is charged up.
My guess is that the cap in your unit had a short.
.
Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Should I have the power outlet replaced though?
yes.
SamT
Now if I could just remember that I am a businessman with a hammer and not a craftsman with a business....."anonymous". . .segundo
You're lucky your hand wasn't in the path of that vaporized metal ejected from the outlet!
No question, replace the outlet. The insulators inside may now be cracked, or you may have left soot trails (which are somewhat conductive) inside the outlet.
Thank you all.The outlet will be replaced. I just have to get it on the list for my electricial demi-god. I am glad that my hand did not end up being nickel-plated in the process. Thanks again for your advice!
You should get Apple to pay for the outlet replacement.
Heh, have apple pay for anything? It's not worth my time or the cost of the repair. It'll simply be addressed when the demi-god comes back to finish the last items on the punch list.When I took the power supply back to the local Apple store, the Apple rep at the genius bar mentioned that this sort of problem is not uncommon with the "duck bill" adapter plugs/power supply shoes and that it was the plug/shoe, not the power supply that was probably shorted out. He plugged the power supply in with a new cable and it worked perfectly... I got a new "duck bill" shoe for the power supply and was sent on my way. As some of you might know, the Apple power supplies have a slide-in poirt for the power "head", which may consist of a standard 3-conductor grounded cable with a slide-in shoe at it's end or the "duck bill", which has a fold-down 2-prong plug. The two prongs on the duck bill can be folded down for transport, resulting in a very compact and tidy power supply. In other countries, the plug attachments tend to be a lot larger, with the UK plug easily being the master of the bunch (and none of them have the fold-down feature either).Moral of the story: replace the duck bill "shoes" regularly and use them as little as possible (i.e. only for travel). Another benefit of the 6' cable with a shoe that Apple also includes is that it is grounded, whereas the "duck bill" shoe is not.