Burn marks on Apple charger plug pins - Page 1
Forum section: electronics / general

author: bd139
author_rank: Super Contributor
timestamp: August 03, 2017, 08:17:49 am
content: Noticed this today. Thought it was interesting. If you look at my Apple charger here there are burn marks on the plug pins. Clearly due to the inrush current when plugging in. I dread to think what this does to the switches in the socket face plate.See attachment

author: Halcyon
author_rank: Unknown
timestamp: August 03, 2017, 08:20:05 am
content: You don't have switched outlets?

author: bd139
author_rank: Super Contributor
timestamp: August 03, 2017, 08:25:02 am
content: I do however I'm lazy some of the time and I wonder what this actually does to the switched outlet contacts.

author: Zero999
author_rank: Super Contributor
timestamp: August 03, 2017, 08:51:13 am
content: Quote from: bd139 on August 03, 2017, 08:25:02 amIt's better to use the switch because it's designed to make/break the load. Whilst UK mains plugs will withstand this kind of abuse, it's not good.

author: bd139
author_rank: Super Contributor
timestamp: August 03, 2017, 08:57:36 am
content: Fair points.I think this lazy happens because the blocks I have aren't individually switched per socket.Can anyone recommend a half decent individually switched trailing socket block at all? (Not Brennenstuhl / generic crap)

author: Electro Detective
author_rank: Super Contributor
timestamp: August 03, 2017, 10:06:39 am
content: All the apple gear I've come across, does to not like to be jiggled into a live power pointBest to use a switch, unless you like apple's replacement prices

author: glarsson
author_rank: Frequent Contributor
timestamp: August 03, 2017, 10:21:25 am
content: Quote from: Electro Detective on August 03, 2017, 10:06:39 amLarge (most?) parts of the world do not have switched sockets. We don't, and I have never seen this cause problems for any of my Apple gear.

author: Electro Detective
author_rank: Super Contributor
timestamp: August 03, 2017, 10:29:32 am
content: Australian 240 volt 'non-round' slit style sockets must be different to yours, they can be very unforgiving to plugs that are forced/jiggled in with power appliedAnyway I'm sick of cleaning black spark gunk and filing down welder style metal spikes from appliance plugs and troubleshooting abused power sockets,so here in oz it's'plug in, then switch on'for me!

author: JPortici
author_rank: Super Contributor
timestamp: August 03, 2017, 10:44:48 am
content: Quote from: glarsson on August 03, 2017, 10:21:25 amOr any gear at all. same for me

author: RGB255_0_0
author_rank: Frequent Contributor
timestamp: August 03, 2017, 10:58:21 am
content: I'm not sure what metal/alloy they make their plugs from but it doesn't look like brass to me. My MagSafe charger features those same black marks.

author: bd139
author_rank: Super Contributor
timestamp: August 03, 2017, 11:02:11 am
content: At least it's not just me.My other apple charger (diddy one for phone) doesn't have these burn marks

author: electr_peter
author_rank: Unknown
timestamp: August 03, 2017, 04:49:05 pm
content: Plug does not look too bad in the pictures. I have seen laptop power supply with Euro plug C (CEE 7/16) in much worse condition (pitting on pins). See added pictures.

author: Ampera
author_rank: Super Contributor
timestamp: August 04, 2017, 02:24:52 pm
content: I live in the US with NEMA outlets (flat prongs, normally seen on cheap chinese crap). We don't have switched outlets (we barely just got shutters on US outlets) and I have never in my life seen anything of this sort. I have never had burnt plugs, and I've never seen it before on US, Europlug, or Shucko (I use all three in my house) plugs.

author: bd139
author_rank: Super Contributor
timestamp: August 04, 2017, 02:28:22 pm
content: You don't have as many volts over there though

author: Ampera
author_rank: Super Contributor
timestamp: August 04, 2017, 02:31:46 pm
content: Quote from: bd139 on August 04, 2017, 02:28:22 pmBut wouldn't it be the current doing it? To be fair a normal UK ring mains circuit is I think around 32A, and a standard european is around 16A while ours are 15A.Whatever, I don't have the EE knowledge to figure that out. I'm here to learn about it, less teach it. I've got computing experience for that.

author: bd139
author_rank: Super Contributor
timestamp: August 04, 2017, 02:34:23 pm
content: I think the higher voltage is more likely to form an arc during the bounce that happens when you plug something in.

author: alm
author_rank: Super Contributor
timestamp: August 04, 2017, 02:40:32 pm
content: What bd139 says, maximum arcing distance (dielectric breakdown of air) is pretty much linear with voltage (obviously depending on socket construction and other factors).Quote from: TwoOfFive on August 04, 2017, 02:31:46 pmTeaching is an excellent way to learn a subject.

author: vodka
author_rank: Frequent Contributor
timestamp: August 04, 2017, 03:39:22 pm
content: Quote from: bd139 on August 03, 2017, 08:17:49 amWhen did you insert the pins on the plug , you didn't hear any sound like spark? I have two charger of laptops when i plugged to plug , it made sounds seemed to sparks(i confirmed that its pins are erosioned).Too, i realized that this trouble always is produced by the Switched Power Supplies, never by the Linear power supplies.

author: G7PSK
author_rank: Super Contributor
timestamp: August 04, 2017, 04:08:13 pm
content: I have seen burn marks like that before on UK plugs, it's due to the sockets, the sping tension on the contacts slacks, it can even lead to fires with a bigger load. Happens more frequently with cheap Chinese sockets and extension leads.

author: TheDane
author_rank: Regular Contributor
timestamp: August 04, 2017, 04:45:09 pm
content: Quote from: vodka on August 04, 2017, 03:39:22 pmIt is most likely due to the low ESR of the capacitor inside, after rectification from mains AC to DC.230Vac rectified is normally over 300Vdc, and most caps have ESR values below 0.1 ohm... The initial inrush current is enormous, if plugged in at max voltages.Protection costs, and Fox ConI wouldn't recommend freezing your SMPS before powering it up, but that effectively raises ESR value, if it's an electrolytic cap

author: Gyro
author_rank: Super Contributor
timestamp: August 04, 2017, 07:46:33 pm
content: Yes, that looks like high inrush current to me too. It reminds me of the crack you hear when you plug the IEC lead into a laptop adapter. A bit surprising for an adapter of that size though.

author: Zero999
author_rank: Super Contributor
timestamp: August 04, 2017, 08:37:55 pm
content: Yes, it's the high surge current, when it's powered up. It's poor design, they should have added something to limit the inrush current. Another option is to not have a big smoothing capacitor and using an active power factor correction unit, but that would probably be too expensive.

author: bitseeker
author_rank: Super Contributor
timestamp: August 04, 2017, 10:28:55 pm
content: This happens to me on 120V with both MacBook Pro and iPad power supplies. Poor design for such "high tech" and expensive wall warts. Granted, the fake Apple chargers are even more poorly designed, but it's highly disappointing that a brand name charger arcs so often.I don't have that problem with my Acer, Samsung, and LG chargers.

author: bd139
author_rank: Super Contributor
timestamp: August 04, 2017, 10:32:21 pm
content: My (genuine) Lenovo one does it as well by the looks. No burn marks but lots of pops.I imagine it stresses the front end rectifiers as well.

author: Electro Detective
author_rank: Super Contributor
timestamp: August 05, 2017, 08:50:46 am
content: Loose, tight, misaligned sockets,silly socket safety shutters that never work properly, or are just plain fkt by improper usage or design (usually the former PLUS latter)bent plug pins,corroded or tarnished contactscheap crappy-Made In Chynna Allleyways-powerstrips/boardsall contribute to DIY fireworks that isn't doing your equipment any favorsMight even blow an internal fuse or trip a sensitive circuit breaker or RCD/GFCI etcNot worth the hassle or drama stressing your electronics every time you plug in and gamble it will work 'like last time'get a switch into the equation ASAP

author: amyk
author_rank: Super Contributor
timestamp: August 05, 2017, 04:30:19 pm
content: Desktop PC PSUs usually have NTC inrush current limiters, but laptop ones might not because having an extremely hot object (they are supposed to get very hot in normal operation) in a sealed case is not a good idea .

author: Zero999
author_rank: Super Contributor
timestamp: August 05, 2017, 05:42:01 pm
content: Quote from: amyk on August 05, 2017, 04:30:19 pmTrue but there are alternatives to NTC resistors, such as using a switch (solid state or electromechanical) to bypass a resistor, when the reservoir capacitor is fully charged. The resistor doesn't get very hot because it's only used, for a short length of time, after the power is applied.

author: bitseeker
author_rank: Super Contributor
timestamp: August 05, 2017, 08:27:46 pm
content: Quote from: Electro Detective on August 05, 2017, 08:50:46 amThat's about the size of it. However, how much arcing is there going to be in that switch?

author: Electro Detective
author_rank: Super Contributor
timestamp: August 06, 2017, 12:08:35 am
content: Quote from: bitseeker on August 05, 2017, 08:27:46 pmEven with a crappy switch it's a one time transient at the switch end and along the cable, that doesn't cause'spot weld'zaps on the device plug or mains socket,as opposed to the straight out jiggle 'n sizzle plugging in(russian roulette...)method to live 240/120 mains.Switches are cheaper to replace, not that I've seen many go bad, especially the domestic style 10 amp rated 2 pole/single throw ones, they last ages, literally!Ano frillsquality power board/strip with individual switched outlets, or just one master switch, is a must have if using a lot of switchmode power warts and chargers,preferably one with a small resettable thermal cutout switch (which most SHOULD have) in case of overloads or heat creating shorts.They fit in the toolbox easily and squeeze fine into most laptop bags

author: Ampera
author_rank: Super Contributor
timestamp: August 06, 2017, 12:14:01 am
content: Nobody else but the UK and AU/NZ have switched outlets, AFAIK.

author: bitseeker
author_rank: Super Contributor
timestamp: August 06, 2017, 06:58:25 am
content: There are switched outlets in the US, but they're separate devices (in separate locations or a multi-gang outlet box). I do like the integrated switches in the UK, etc. The closest thing I've found here are power strips with individual switches for each outlet, but they aren't prevalent either.

author: bd139
author_rank: Super Contributor
timestamp: August 06, 2017, 07:01:58 am
content: Indeed I spent an hour last night trying to find some. The nearest thing i can get is a strip of normal wall plates sockets. And that's stupid expensive. I really need a bench TBH with a proper set of switched sockets on it. I'm not sure my wife would be up for that though as we're not rolling in space.

author: bitseeker
author_rank: Super Contributor
timestamp: August 06, 2017, 07:04:19 am
content: Oh, wait. I do remember seeing a combo switch/outlet that goes into a single gang box. Here are some pics of a couple of styles. They're still not as space-efficient as the UK ones.