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Sparking Ideas

Thermaltake Box and Ground Box 500 Wide.jpg

Carol and I traded offices here after completion of our downstairs rehab, and while the process is ongoing (much stuff is still lying around in boxes) I’ve come upon a problem I didn’t have before. Back in late March, I touched the metal bezel of a conventional USB 2.0 port on my desktop quadcore, and drew a 1/4″ spark. As you might expect, the machine died instantly. The new carpet generates a lot more static than the old carpeting did–and our customary 7-9% humidity doesn’t help.

Why the USB port bezel wasn’t grounded is a mystery, since the wire coming out of the top panel encapsulated port assembly was screwed tight to the case, and the case to the third wire. I can only assume that something was broken inside the port assembly. I’ll tell you right now, I am not going to buy any Antec cases anymore. This is the second one that’s gone bad in precisely the same way: wonkiness in the front/top panel port assembly. Furthermore, I had to destroy the top panel to remove the port assembly, since the case metal completely blocked access to two of the plastic release tabs. No wonder they wouldn’t sell me a replacement port assembly, since the assembly could not be changed without destroying the case itself. Antec is off my list, now and forever.

There’s nothing bleeding-edge in the new machine. The mobo is a Gigabyte Z68A-D3H-B3, if that means anything to you, with an Intel Core i5-2400 Sandy Bridge processor on it. The cores run at 3.1 GHz, vs 2.4 GHz for the old machine. I had them put it all in a Thermaltake V3 case, which is smaller and simpler than the Antec Nine Hundred I’ve been using since late 2008. I am not a gamer and am quite content with integrated graphics, so elaborate cooling machinery is unnecessary. The case fans are quiet (though one of them seems to rattle periodically) and overall I consider it a winner.

Now to figure out how not to kill the new machine. The quick fix was to pull a homebrew 350V power supply off the shelf and plug it in beside the new quadcore. The aluminum chassis is grounded to the wall through the 3-wire cord, so touching the chassis before touching the quadcore should do it. (The blue mouse pad is just to keep the supply from scratching the table.) I know it works because I can pull quite a spark by touching it after scuffing around the lower level. Better still, if I hold an NE-2 neon bulb by one lead and wave it a few inches from the grounded power supply, I can see the static bleed off through the bulb, without even touching the other lead to the chassis. (Turning the lights off makes it more dramatic, but I can see the orange flickers in full daylight.)

The neon bulb experiment suggests that something more graceful than an old power supply could be put together as a grounding station. I have a wonderful 5″ bronze worm wheel given to me by Carol’s dad circa 1987, and with a little skill and some copper pipe fittings could build something with a VR-75 tube at the center, and the gear as the touchplate. Touch the plate, flash the tube, kill the static. I’m going to lash it up before putting a lot of work into it, but I see no reason why it wouldn’t work. More as it happens.


  1. Tom R. says:

    I have had a similar, but far less severe problem with one of my PC’s. Fortunately the worst problem I have had is an unexpected re-boot when I would try to plug in a USB memory stick in one of the front panel ports.

    I suspect these ports are just connected to the motherboard with a piece of ribbon cable and a header and there is no attempt to ground the shell. Of course, yours sounded like it WAS grounded. I have a USB extension cable plugged into one of my rear ports which ARE grounded and I touch the shell of that JUST before plugging anything into a front port.

    The VR-75 tube for a steam punk static eliminator sounds cool.

    Don’t blame it too much on the low humidity. I don’t think we ever get much below 30% even in the dead of winter down here. Summer is always close to 100% — and we still get static discharges!

  2. RH says:

    There are commercial products for treating carpets to reduce static. There are also home remedies, generally based on spraying diluted fabric softener on the carpet. Apparently all such treatments are temporary, but it might be worth a try.

    1. Yes, the reports are pouring in. It’s worth a try; lord knows, fabric softener is cheap. I’ve also discovered that the strength of the spark is shoe-specific: When I wear my Clark’s Natureveldts, I generate enough voltage to drive an 811A; when I walk around in my socks, not so much. It’s been very dry here, which may make a difference. Then again, it’s *always* very dry here.

  3. Gary Kato says:

    I remember being at the first CES that the game company I was working for (Imagic) showed off its wares. It was Las Vegas and someone had decided to have carpeting in the booth. We were zapping EPROMs left and right until someone went out and bought some anti-static spray to put on the carpet. It worked.

  4. Chuck Waggoner says:

    Hmm. I do not recommend the anti-static stuff. Back when I worked in Chicago TV in the mid-’80’s, we had carpeting in the telecine and videotape rooms. Even though there was a commercial humidifier that produced an environment close to Galveston on a summer day, there was still a lot of static.

    One of the maintenance guys sprayed the whole area with anti-static compound. Ooooh! Wrong thing to do. We had two of those IBM drives that had the big round plastic cake top with T-handle that served as storage for our relatively new computer still frame storage. Both were destroyed, and since one was backup to the other, all images for the station were destroyed with them.

    In the tape room, magnetic particles in the spray floated around and infected most of the videotape machines (which used 2″ wide tape and were monster machines in that day. Only the Ampex video cart machine escaped those magnetic particles, which actually erased magnetic information from the tape, and caused a checkerboard of tiny little white dots in the playback picture.

    If you have magnetic anything, don’t use the static sprays.

  5. Terry Roe says:

    I’m glad to hear it’s not just me. I have two machines I built with Antec cases and both have this front panel problem. I thought it was something I did wrong building the machines. I couldn’t for the life of me figure out what it might be since the problem was in the front panel which comes as part of the case.

    Sigh. Other than this problem, I really liked the Antec cases.

  6. Jack says:

    An anti-static workbench mat on the table top and an anti-static chair mat or carpet segment should do the job.

    These are high enough resistance to discharge static but not low enough to provide a safety hazard should you come into contact with the 120V hot line. The mats connect through a high resistance connection to a suitable ground point such as the ground pin on an AC outlet.

    Dave Jones of the excellent EEV electronics video blog has three related videos tracking down the source of a large voltage spike seen on an oscilloscope under certain circumstances. Turned out to be the chair he sat on. When he got up quickly, the chair (gas spring design) generated enough of a electrostatic charge to induce a surprisingly large transient on his bench oscilloscope.

    The particular blogs are no. 14, 20 & 21; all are viewable from … however I have to warn you that it’s impossible to watch just one or two of his videos. You will find yourself wanting to view all of them.


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