USB spark issue when I plugged in a powered external USB hub or external HDD?

[trenzterra]

As above, I am seeing sparks whenever the tip of the USB cable of a powered hub or HDD touches the USB port. It is somewhat similar to this: http://www.youtube.com/watch?v=MCZFmRYKxYg just that with my rear ports with my PCI-E USB3 card it is the most obvious (and most scary). Sometimes the sparks are large enough to trigger the 'device has been plugged in' sound in Windows! It happens with my front header ports as well.

All devices are grounded by a 3-pin plug and plugged into the same Belkin power surge protector. I have tried other outlets with the same problem. Curiously, my laptop does not exhibit the same problem even when it is connected to the mains itself.

Thus, I was wondering what could be the issue (I suspect a ground loop issue) and how I could go about getting it solved? Would getting a new PSU help?

Thank you!

 

[skit75]

Are you using an iMac like the video or a PC?

 

[trenzterra]

Are you using an iMac like the video or a PC?

I am using a PC. Here are my specs:

Intel i5 2400
Asrock z68 extreme 4
Sapphire radeon 5850
Fsp aurum cm 650w psu
Sound blaster Z

I also noticed that when the powered USB cable comes into contact with the metal part of my expansion cards my speaker picks up the noise/interference too. And I don't know if it's related, but recently I noticed that sometimes when I shut down my computer it reboots instead. But I didn't think much of it until now.

What could be at fault here? Honestly I'm hoping changing the PSU would solve everything but I wonder if this would even help...

Out of curiosity, I tried to plug my powered USB hub and external hard disk together by themselves (I. E. Without connecting them to my pc) and there weren't any sparks.

Any ideas? Thank you very much!

 

[trenzterra]

I bought a new PSU but the problem still persists!

Sigh, what should I do next?!

 

[skit75]

I would check to see if fiber washers were used to mount the motherboard. Remove them if they are there.

 

[trenzterra]

I'm not using the fibre washers. My screw is attached directly to the standoffs.

And yes, it seems to spark only when in contact with the PCI-E expansion cards.

Faulty motherboard? Or..?

 

[trenzterra]

I just realised:

1. For my USB hub, the 3rd pin is plastic, which means it's a dummy
2. For my external HDD, though the end is a 3-pin, the other side is a 'figure-of-8' plug that connects to the adapter.

Does this mean that in both cases, the ground is fake?!

In such a case, how do I protect myself from any electric shocks from improper grounding of the device?

 

[skit75]

Sounds like a floating ground.

 

[trenzterra]

In that case is it considered normal behaviour, or..? Is there anything I could do to improve the safety? Thank you

 

[trenzterra]

I just used a test pen and indeed both devices light up my test pen. The test pen doesn't light up when I touch the bare metal parts of my case.

 

[trenzterra]

Given most external USB devices use 2-pin anyway (e.g. printers etc.), I decided to do some further testing.

I had a spare desktop lying around so I used that to test too.

I realised that the sparks occur even if my entire system is unplugged as long as I plug in my monitor. I tried two monitors, and used both DVI and HDMI, and used both onboard and my PCI-E graphics card, with the same result. However, the spark was far more obvious with my NZXT Beta EVO case compared to my spare desktop, which was using a Sharkoon W-1000 case.

I realised that the sparks were generated most often when the USB connector rubbed against the mesh slot covers while being in contact with the bar separating each of the PCI brackets.

I figured it might be something to do with the meshed slot cover, so I replaced it with the smooth metal covers from the Sharkoon W-1000 case and it seems that the sparks happen rather rarely now.

I'm really curious how a meshed slot cover could have caused the sparks while a smooth metal cover doesn't. Is it because it's an uneven surface or something?

 

[skit75]

It could be something simpler like the paint on one being more conductive than the other.