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 Post Posted: Mon Oct 16, 2017 1:00 pm 
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Hi guys,

So, in February 2014 i bought a new iMac from Apple (it is a late 2013 model). It's only a leisure machine so it's not really worked hard at all. I have two (mains powered) external HD's connected to it: one is a clone (2GB), the other is my iTunes library (3GB). The 2GB is on it's way out I think as it unmounts itself. I do have an external offsite clone of my iMac so I'm not too fussed about that. These occupy USB slots 1 & 2.

Anyway, a few months back, I posted about an issue with my iPhone and it playing up when I connected it to my iMac. It would connect and disconnect etc (USB slots 3 & 4). I thought it was an issue with the battery, but Jonah suggested I try digging out the pocket fluff from inside the lightning connector. So I did. And it worked.

However, the problem then reappeared. I couldn't work it out, when the iPhone was plugged in at the mains, it never behaved like it did plugging into the iMac. Perplexed me it did, but I've just learnt to live with it as I figured it was my iPhone.

Today, I wanted to sync my iPhone, so plugged it into both slots 3 & 4 and all it done was disconnect/reconnect. PITA. So I ejected the flagging external HD and popped my lightning USB into it's USB slot. The iPhone connected and didn't misbehave at all; it's sitting here now syncing, doing what it's supposed to do.

So, this leads me to think that it's an issue with the USB slots on the iMac (specifically 3 & 4). Now, before my years warranty was up on my iMac, I made a genius appointment and took it to Apple as there was a very slight spark around the USB slot when any USB touched the iMac case upon insertion. Apple diagnosed it and said that it must be an issue with whatever mains powered externals that you are using, and told me that it wasn't harmful and to carry on using it like normal. I explained the my equipment was fine etc etc, but they basically told me to go away. To this day, it still sparks, not a lot, but enough for me to be able to see if a USB connector is run around the edge of the USB slot. The fact I've now isolated my iPhone connecting issue to the iMac not the phone makes me wonder where I stand with Apple. There is clearly a fault with the USB sockets somewhere, but my warranty is well out-but I did report the issue initially and now I can demonstrate that there is a fault.

Where does this leave me in the grand scheme of things? Would you pursue it at all? Do I have a 'case' so-to-speak? When I thought I had an issue with my Apple Watch, I took it to a Genius and although they found no-fault, they took photo's and documented the problem, saved it to my ID and started that if any further issue was to develop at a later date or after the warranty was up, they have a record of it.

Could I go in with the Consumer Law aspect, as quoted on the Apple website?

https://www.apple.com/uk/legal/statutory-warranty/

Thoughts?
Dan

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 Post Posted: Mon Oct 16, 2017 3:13 pm 
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I have had the exact same disconnection issue on the same model iMac (mine is a 27"). I have found that ports 3 and 4 can be a bit temperamental with certain USB cables.

I had a Woodford cable which was supposed to be one of the highest quality 3rd party cables you can buy and, to be blunt, it was a piece of shit. It ALWAYS caused connection issues when plugged into ports 3 and 4 (and indeed whenever it was plugged into my iPhone). I ended up throwing it away.

I have found Apple or Anker cables to work well.

I haven't had the sparking issue, or should I say, I have never seen it because I can't really see the back of my iMac. I may try to see if it happens for me.

FYI Ports 1 and 2 in my iMac are always filled by two external hard drives so they never get any connect/disconnect use.

As for where you stand with Apple, I would ring them and say you are having this issue. It has already been documented so they can advise you what you should do. It may be they suggest a Genius appointment. If so, you make sure you choose which store you use. I had a dead MBP a few years ago, I went to the Bullring store who diagnosed the issue and told me to cough up £700 for the repair. It was just out of warranty so I rang Apple, complained, they made a Genius appointment at Solihull who then diagnosed that it was a known issue with that model and repaired it free of charge.

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 Post Posted: Tue Oct 17, 2017 1:05 pm 
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Jonah wrote:
I can't really see the back of my iMac.

An iMac is a beautiful thing, but placing all the ports on its backside is one of the worst design faults ever IMO.

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 Post Posted: Tue Oct 17, 2017 2:57 pm 
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MacBiter wrote:
Jonah wrote:
I can't really see the back of my iMac.

An iMac is a beautiful thing, but placing all the ports on its backside is one of the worst design faults ever IMO.

Yep, and they aren't easy to actually use either so you get things like this made.

Amazon link

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 Post Posted: Tue Oct 17, 2017 3:48 pm 
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Agreed. Fiddly, the USB never goes in first time, so you turn it around, still doesn't go in, pull the iMac forward so you can see and the screen goes black because you've accidentally pulled the power supply out ever-so-slightly :roll:

Thats a neat idea to keep the port of the desktop. I can't comment on the build quality, but I've always thought that this was quite a nice neat solution. I know it sits on the desk, but on the stand it looks quite nice. THIS looks quite neat too, smaller profile and off the desktop.

In relation to the matter in hand, I've tried to capture a video of the sparking. The video itself is quite dark in an attempt to highlight the sparking, found HERE (sorry, can't figure out how to embed the video!).

I did wonder if ports 3 & 4 were designed to operate at a lower voltage than 1 & 2, and with 1 & 2 being in use all the time on my mine, whether this was having a detrimental effect on ports 3 & 4. This may explain why the iPhone behaved properly when plugged into port 2. I am looking to replace both HD's with a 4TB in the future so reducing them to one and freeing up a port, but that won't be for a while. Doesn't explain the sparking though. No issue with my Lightning cable, but I am looking to buy a new, longer one soon, and I quite like the fabric Anker cables, so i'll opt for one of those.

I'll try and give Apple a call this week and see what they say, and see whether I can get an appointment next week during half term.

My local Apple Store are a bit hit and miss. They were really rude to my Dad on one occasion, and I recently had an issue with my Watch which they were really, really unhelpful about. However, I've also had some positive results there, mainly with iPhones.

Eitherway, I don't think that sparking is good.

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 iMac 21.5", 2.7GHz i5, 1TB Fusion Drive, 16GB RAM, 10.13
 iPod Shuffle 2nd Gen (Product) 1GB
 iPhone 6s, Space Grey, iOS11, 64GB
 Apple TV 4, 32GB
 Apple TV 3
 Watch Nike Edition, 42MM
Raspberry Pi 3b/Retropie 4.1


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 Post Posted: Wed Oct 18, 2017 6:26 pm 
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DanielMoore wrote:
Thats a neat idea to keep the port of the desktop. I can't comment on the build quality, but I've always thought that this was quite a nice neat solution. I know it sits on the desk, but on the stand it looks quite nice.


That would work on my 2011 iMac but ... it's unpowered! Wouldn't it overload the USB port it's connected to if you used all 4 ports?

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 Post Posted: Wed Oct 18, 2017 6:35 pm 
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I think this is an induction hum loop developing between your computer and whatever the USB device is connected to. In common with a lot of modern equipment, the iMac is double insulated, in other words the case of the iMac is not actually physically connected to the ground lead on your power socket. It is left to float free, in terms of potential. And there is a small (it will be measurable by a suitable test meter) 50 Hz a/c difference between the USB lead and the case of the iMac, which is a small induced voltage - though it will be quite a low voltage. But even so large enough to cause a small current to be able to cause some minor sparking to be generated there sometimes. It is harmless, but disconcerting.

It is sparking between the 'earth' common outside of the USB connector and the case of the iMac, it has nothing to do with the power or data connections within. What is the USB lead connected to? If you have a multimeter put it on AC setting and see if you can detect a voltage between the two, when they're not connected.

It is most likely caused/aided/abetted by one/some of your peripherals that are powered by mains.

No, the hum loop theory doesn't seem to fit, but a small induced leakage current does.

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