[crazy4laptops]

Today at my university IT job, I was tasked to setup 15 Elgato Eyetv One hdtv tuners in the Mac multimedia lab.

For reference- http://www.amazon.co...1/dp/B002XISW02

I had hooked one up to the mac and as I was holding the tuner in my left hand and the coax cable (university run cabletv) in my right and the moment had touched the cable, I noticed some mild electrical current running through my left thumb. Once I let go of either the cable or the eyetv, it stopped. I only felt it coming from the eyetv. I pulled 3 other tuners at random, they all did the same thing! So I suspect there's some power leakage from the USB.

I don't think this is normal after being zapped twice by 30,000µF camera flash capacitors (the warning labels are there for a reason my friends) So I have a bit of hands-on experience with a bit of voltage/current flowing through both hands/arms (thank goodness not my heart) I am planning on bringing the voltmeter with me so I can test how much current is coming from the eyetv's, and I'll update on that sometime Monday.

I have called Elgato once I realized what was happening. The tech had never heard of this happening and assured me that the senior techs were going to look into this right away!

This post has been edited by crazy4laptops: 27 April 2012 - 09:16 PM

[mjd420nova]

BE CAREFUL SAFETY FIRST This sounds like a half potential mix. Check for other users/devices that have gotten the neutral mixed with a ground. A ground falt interupter should have tripped if this test area, work area is up to code.

This post has been edited by mjd420nova: 28 April 2012 - 03:00 AM

[crazy4laptops]

mjd420nova, on 28 April 2012 - 02:59 AM, said:

BE CAREFUL SAFETY FIRST This sounds like a half potential mix. Check for other users/devices that have gotten the neutral mixed with a ground. A ground falt interupter should have tripped if this test area, work area is up to code.

I know half-potential is an electrical term, but I don't know what it means exactly...

However, the building should be to code (government standards are a must) No one else has commented on being zapped by the computers, so the tuners are probably the culprit. Since the tuner is powered by USB, I don't think that's enough to trip an outlet GFCI (I may be wrong on that) Plus, the macs are plugged straight into the floor.

[coastie65]

Sounds to me like something wasn't properly grounded and you my friend, made a very good ground.

[mjd420nova]

Half potential happens when two wire line cords get mixed with non polarized plugs and grounding either one accidently or other wise will give you a either neutral to ground or hot to ground.. It is usually around 60 volts, a tingle to those accustomed and a noticable shock but not a jerk back response.. The problem comes when devices with opposite inadvertent groundings through any number of devices on the same line can create a loop that eventually presents the full 120 volt potential between two grounds. I've seen serial cables, CAT5 cables and yes, even USB and coax cables melt, burn and flame on before breakers tripped. Failures of bricks can be a hazard if left on with no load. Isolation with surge protectors and power strips helps but can compound the problem with more added devices on a single loop. Users that had the most problems I've encountered was the Motorola radio charging stands. Their bricks were dropping like flies when new. After doing an in house upgrade and driving the charging units with a single higher current power supply. One unit for each six bricks replaced. When rotation of use and charging reached a no spare situation, a power outage overnight left them with no working radios by noon. The chargers went on UPS units that could support three chargers for eight hours, long enough to get a full charge of half the available units. Their bricks developed shorts within and often melted their pastic cases and early failure stages was the shorting wires in the transformer winding to one side of the wall outlet, hot or neutral. They eventually melted.