How can I ground my computer and audio setup?
September 10, 2004 6:53 AM   Subscribe

My gear is giving me electric shocks, and I don't know what to do. [more inside]

I've got a complicated setup with two computers and lots of external peripherals and audio equipment. Cables run in all directions, with everything connected to everything else. The only high-wattage devices I've got are a very old stereo amp and a monitor.

Every once in a while I'll get a small shock from touching something. I've had it happen with a DVD burner, one of the PCs, and an electric guitar (which is plugged through some electronic gear into a PC, not into a guitar amp). It's been going on for about a month.

I haven't gotten fried yet, and neither has my equipment. Should I be really worried? I'm completely ignorant about electricity, so can anyone give me an idea about what might be wrong, and recommend things I can do to troubleshoot this?
posted by fuzz to Home & Garden (16 answers total)
 
Ground it?
posted by ParisParamus at 6:55 AM on September 10, 2004


Are you cheating by defeating a thre--pronged plug somewhere?
posted by ParisParamus at 6:56 AM on September 10, 2004


Yeah, my apartment has only one grounded outlet and two ungrounded ones. I'm using power strips. The stuff that gives me shocks doesn't have grounded plugs, so even if I plugged the power strips into a grounded outlet, wouldn't the equipment not be properly grounded? Should I make sure that all grounded plugs are plugged into grounded outlets?
posted by fuzz at 7:00 AM on September 10, 2004


Fuzz, you could do that, or you could buy one of those adapter plugs with the wire which attaches to the outlet plate (and thus the outlet box, which is grounded). That should work. If not, you would probably need to go for attaching ground to the heat pipes.

You might also consider installing three-pronged outlets--not that tough, really.

Let me guess: you live in Brownstone Brooklyn?
posted by ParisParamus at 7:11 AM on September 10, 2004


Spain? 220 volts? I don't know a thing about your electric system (including whether the outlet boxes are grounded)!
posted by ParisParamus at 7:13 AM on September 10, 2004


yes, you should make sure that all grounded plugs are plugged into grounded outlets. the other stuff shouldn't matter.

is it the equipment, or you? depending on the clothes/shoes i wear, i get a shock when i touch the handle of my office door. it might be that you're getting a static charge and discharging it to earth (in which case, if it really bothers you, get an anti-static bracelet from an electrical supply store, connect the cable it comes with to earth, and touch the bracelet before touching anything else; or wear different clothes/shoes!).
posted by andrew cooke at 8:16 AM on September 10, 2004


Fuzz, you could do that, or you could buy one of those adapter plugs with the wire which attaches to the outlet plate (and thus the outlet box, which is grounded).

You can't really rely on the outlet box being grounded; sometimes they are, sometimes they aren't. Look for an uninsulated wire screwed directly to the box.
posted by Galvatron at 9:16 AM on September 10, 2004


I must second Galvatron: I live in a brand new building in Brooklyn built by the lowest bidder. Not all of the outlets are grounded.
posted by o2b at 9:27 AM on September 10, 2004


Heh - fuzz, I living in BCN too and have the same problem. When it comes to wiring, the Spaniards are crap! Most of my sockets aren't grounded, and even the screws on the bottom of my laptop or my guitar strings will shock me sometimes. Either live with it, or get the place re-wired.

Fancy a BCN minimeet? ;-)
posted by benzo8 at 10:07 AM on September 10, 2004


Just curious, what preamp do you use to get your guitar into your PC? I've been trying to find something for that situation lately.
posted by abcde at 11:59 AM on September 10, 2004


"You can't really rely on the outlet box being grounded; sometimes they are, sometimes they aren't. Look for an uninsulated wire screwed directly to the box."

I always wondered what that was about, having grounded boxes, but not outlets....

By amateur radio teenage days--WB2MMR!--lead me to suggest connecting that ground wire to the radiator (if there's no grounded boxes).

Or, just wear rubber gloves!
posted by ParisParamus at 2:27 PM on September 10, 2004


Ok. Here you go, you have hot -> chassis leakage on those devices, and a lack of enough neutral -> chassis connection to bleed it off. That could be due to a crap power supply in them.

You could try to get them fixed, tell a repair shop to check for leakage current on the case (even most "perfect" two prong stuff will still show about 60V on the case so you must measure for current).

The higher the leakage current, the more likely you'll get a shock.

IF you don't want to get them fixed, you can , if you do *NOT* connect the deives to anything not plugged into this, plug all these devices into an isolation transformer.

If every item is not on an isolation transformer, and you hook the one that isn't to the ones that are, you are back to square one.

Your other choice is to connect the chassis of all the items to a proper ground and let the problem drain away. It might damage your devices over time, and could leave your home a bit dangerous, as often ground is clamped to your water pipes.

HTH. I had a TV that did this on the antenna jack (the model was supposedly "famous" for the problem), a 1702 commodore monitor with this problem, and a 1984 vintage Zenith VCR with this problem. A lot of 2700 Echostar IRDs seem to have leakage problems (I can demonstrate it), however, those are solved with the installation of a 3 prong grounded plug connected to the chassis.

Note: It seems if you hook a bad device to a good one, the problem will slowly ruin the good device and render it with the same problem. At least, that's why I think all three of those items got that problem.
posted by shepd at 5:42 PM on September 10, 2004


Thanks everybody for the answers! I'm going to spend today rewiring everything to put the three-prong plugs on the grounded outlet and see if that works. My outlet plates are in plastic, and I don't have any radiators or pipes at hand, so grounding the other stuff is going to be difficult.

I'm really hoping that works, because if shepd is right, I'm going to have to check about 15 pieces of equipment. Any way to figure out which one is bad without bringing them all into a repair shop?

abcde, I'm using an old Boss BR-8, which is incredibly easy to use and has pretty decent Roland amp simulators and effects (as long as you tweak the presets). That runs into an M-Audio Quattro, which connects to the PC via USB. If I were buying today, I'd have a hard look at the M-Audio Firewire 400 with a Line6 Pod, or else a Line6 GuitarPort.

benzo8, sounds like a great idea. E-mail me (I can't find an e-mail in your profile).
posted by fuzz at 2:05 AM on September 11, 2004


I have a GuitarPort, but I really don't like the POD/GuitarPort sound, really fake to me. The Guitar Rig demo without a preamp sounds much better.
posted by abcde at 11:27 AM on September 11, 2004


Oh, and fuzz, there's now a PODxt that lets you go in direct like the GuitarPort using the same software, so there'd be no need for a separate USB interface.
posted by abcde at 11:41 AM on September 11, 2004


>Any way to figure out which one is bad without bringing them all into a repair shop?

Choice #1: Cheap, easy, and painful, probably dangerous.

Plug each item in one at a time. Touch the case. See what shocks you and what doesn't.

Choice #2: Easy. Not cheap or painful.

Get an AC ammeter (part of a decent multimeter).

Plug each item in one at a time. Set your meter to measure AC milliamperes. Put a probe on one end of the case (obviously a conductive part, such as the sheild of a connector -- plastic is a waste of your time), the other probe should go through a resistor to limit shorting current (for 120 V, use about 100 ohms, for 220 V try something higher), and the other end of that resistor should go through some wire to an appropriate ground (you'll need to use your three prong plug for this). Ground is the half moon prong at the bottom in the middle of the plug in North America.

You should get an extremely low reading on your ammeter. If you get anything over, say, .1 A (100 mA), you could die if you touch the case! Anyways, if you're getting less (you should be!) you can remove the resistor and test the full leakage current straight through the meter to ground. This table will explain the pain and danger zones to you. Anything above 5 mA should be considered dangerous and should be a candidate for a professional to test and repair, if needed.

Obviously, while doing all the above you should ensure you are insulated from any of the connections you are making. Use electrical tape on open joints. Insulated alligator jumper clips will make your job easier.

Note the neat thing about electricity: If you want to survive an electrical shock, bigger is better. The fatality zone is right in the middle. Of course, too big a shock will take you from rare to well done, so that's bad.
posted by shepd at 2:22 PM on September 11, 2004 [1 favorite]


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