Thunderbolt port blew up

[Silvrbill]

The Thunderbolt spec is 18 V at 550 mA.

Operating normally i'm sure that's the spec.
However when a ground fault is introduced the normal operating current is irrelevant. Ground faults can carry an enormous amount of current for short periods.
Ground faults have the ability to surge through protection, whether it is a fuse or a breaker.
They may or may not trip a breaker or blow a fuse instantaneously.
I'm a high voltage lineman, over 35 years.
I've seen it happen over and over again.
The destruction of the TB cable/connection and the pitting on the ground and neutral prongs tells me they took a very large surge of current.

 

[westom]

Thanks for the input. I'll call an electrician on Monday.

Drambuie provided a useful reply. Be concerned about others. For example, that three light tester can report some defects. But it cannot report a wall receptacle as good. Even many house inspectors do not know that. And due to the number of tests to find defects, then no house inspector is expected to find all defects. House inspectors only look for the most typical defects; are never expected to find all.

No voltage (ie less than 2 volts) should have existed between the neutral prong and safety ground prong. Blackness indicates a voltage existed.

Meanwhile, no damage must occur even when that voltage exists. IOW multiple defects had to exist to create what that picture shows. So yes, get an electrician and show him the evidence (blackness on the plugs). And also take the entire system to the shop so they can determine what defect made possible damage from a miswired wall receptacle. To have you damage required multiple defects.

 

[Nightarchaon]

That is strange.

I'm using a TB cable manufactured by Sumitomo Electric here in Japan with an external SSD enclosure I run OS X from. I'm not sure what "official" means but mine never gets more than slightly warm to the touch at the plug. The cable itself doesn't even get warm.

Mine is official in the sense that it was bought at an apple store and is apple branded

the cable doesn't get hot, and ive not tried using it for anything other than a monitor connection, so maybe connecting to a drive uses less power or something, but the actual dongle end, the connector, gets hot enough at each end that it had both begun to discolour the plastic of the cable where it left the connector.

since i discovered that, and found the plastic was soft enough when i pulled the cable out that it left a finger print in it, i binned the cable and haven't used the ports since, im not spending a small fortune on another cable.

 

[thedeske]

Home inspectors are idiots. I can't even begin to describe all the things ours missed when we bought our place (or willingly chose to ignore). You cannot rely on them to tell you anything- other then that the building is still standing.

I have only ever seen this kind of damage once before, and that was when an electrical fault lit up the ground line with 120VAC. The damage to the equipment (an audio studio in this case) could best be described as "explosive"- numerous components erupted in flames, others simply obliterated themselves into various charred fragments.

The fact that your grounding pin has arc marks on it (!) tells me that there is something direly wrong with that outlet. You are risking your own life by ignoring the possibility that you have a severe ground fault somewhere in your house. If there really is 120VAC across that terminal, it means that any metallic appliance that you have plugged into the same circuit is going to have a live chassis as well. This could kill you if you touch it.

Seriously. Get your electrical checked out. Catastrophic explosive failures like this should NOT be taken lightly.

I second this. An arc can damage things on the wire 20-40 feet away, and you won't know it until it fails or BURNS. Good ol 110 packs a nice punch in the right setting. Leave that circuit off until you FIX IT!

 

[Anitramane]

I don’t think it’s the display cables fault… I mean, how?

 

[SaSaSushi]

the cable doesn't get hot, and ive not tried using it for anything other than a monitor connection, so maybe connecting to a drive uses less power or something, but the actual dongle end, the connector, gets hot enough at each end that it had both begun to discolour the plastic of the cable where it left the connector.

since i discovered that, and found the plastic was soft enough when i pulled the cable out that it left a finger print in it, i binned the cable and haven't used the ports since, im not spending a small fortune on another cable.

I can't imagine that the plugs getting hot enough to partially melt would be normal, no matter what device you're connecting it to. I also definitely wouldn't have continued using that cable, but I would have wanted to know why it was a fire hazard and investigated whether it was defective, official or not.

 

[hfg]

It is normal for Thunderbolt cables to get warm at the connectors. To reliably handle the high data rates, the cables are tuned transmission lines and there are line driver electronics at each end configured for the length and characteristics of that particular cable.

I have found some "cheap" cables supplied with enclosures seem to get hotter than normal, and I don't use them for everyday use. I have had good luck with Apple and Elgato Thunderbolt cables and they only run slight warm to the touch.

I can't imagine that the Thunderbolt cable could possibly fail and cause the damage in the OP. I can imagine that a AC fault passed through the ground conductor of the Thunderbolt cable would cause the damage as shown in the photos.



-howard

 

[westom]

I don’t think it’s the display cables fault… I mean, how?

A defect could have always existed. Then combined with another minor fault in the wall receptacke, now 120 volts is passing destructively through digital electronics.

All electronics contain multiple protection so that this does not happen. Assuming two defects existed simultaneously, then many different reasons could explain this damage. A mistake is to speculate damage only due to one defect. Until both existed, then everything acted normal - even though maybe one defect always existed.

We know one fact. From a blackened plug, a significant voltage existed between safety ground prong and a neutral prong. No such voltage difference should exist. That implies a defect. Could be reversed polarity. Could be floating safety ground. Could be open neutral. Many other reasons may exist. So many that nobody here can draw conclusions.

We only know one tiny fact from observation. A major voltage existed between two AC prongs that should not have existed. Nobody, but some professionals identifying multiple defects, can say anything more and useful.

 

[joe-h2o]

Operating normally i'm sure that's the spec.
However when a ground fault is introduced the normal operating current is irrelevant. Ground faults can carry an enormous amount of current for short periods.
Ground faults have the ability to surge through protection, whether it is a fuse or a breaker.
They may or may not trip a breaker or blow a fuse instantaneously.
I'm a high voltage lineman, over 35 years.
I've seen it happen over and over again.
The destruction of the TB cable/connection and the pitting on the ground and neutral prongs tells me they took a very large surge of current.

That's what I'm saying - I was replying to someone who is saying this is a fault with the thunderbolt cable or the controller and not a ground fault.

My assertion is that this is a ground fault at mains voltage (120V), and that the cable took the hit because it was exposed to a current and voltage that it was just not designed to handle - probably because the monitor had no grounding and it discharged the floating chassis to ground via the iMac's ground pin.