Question USB cable melted after plugging into PC front IO

Jun 2, 2021
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Wasn't sure where to post this because I don't know if this is a problem with the USB cable, case, motherboard, or something else.

Case: Be Quiet Silent Base 802
Motherboard: Gigabyte Z590 Aorus Elite

I just built a new PC and everything seemed to be going well. I grabbed a USB to micro-USB cable out of a box I use to store cables and plugged it into a front USB to charge my phone later.

I started cleaning up a bit and could smell something burning. I looked around and couldn't find anything out of the ordinary, so I assumed someone was burning something outside and it was coming through my window.

I then went to grab the USB cable to charge my phone and realized that it was smoldering. I unplugged the cable which was very warm to the touch, and the micro-USB end had melted at least an inch. There was a lump of melted plastic/rubber under where it was laying.

So at this point I don't know enough about this stuff to know if this could possibly have been caused by a bad/damaged USB cable, or if something is wrong with the PC. As far as I know everything is connected properly and nothing else seems wrong with the PC, it's been operational the entire time.

Any idea about what could cause this? I'm kind of afraid to test by trying another USB cable.
 

InvalidError

Titan
Moderator
If the cable was just laying there with only the type-A end plugged into the PC and micro-B not plugged into anything, there shouldn't have been any current flowing through the cable. That would definitely be a defective cable that has shorted out.

I'd be a little worried about the PC passing enough current to melt the cable without tripping some form of protection like a 2.6A self-resetting polymer fuse for cheap boards or e-fuses for fancier ones. It takes a fair amount of power to get a cable to melt itself in open air.
 
Jun 2, 2021
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Correct, just the type-A was plugged into the PC and the micro-B wasn't plugged into anything yet.

Based on your second sentence, do you think anything could be wrong with the board? I've had it running for a few hours just watching some Twitch, including while the cable was burning. Everything seems ok. Do you think I should try another cable tomorrow while monitoring it? I also checked the port after I removed the cable and there was no visible damage or heat, just the cable that was quite warm to the touch.
 

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