Will this TV kill me redux

May 2, 2009 11:06 AM

How dangerous is it to take apart an old TV if it has been unplugged for many months?

I have an old TV - 19" Samsung from the early 80s - that I would like to disassemble in order to use the shell for an art-type project. I've seen this question and warnings elsewhere on the internet that digging around inside a CRT TV can be pretty dangerous. This TV has been unplugged since last October, so for about 7 months. Is that long enough to obviate the worry about voltage issues in the CRT?

posted by yarrow to technology (15 comments total)

Probably still dangerous. Better safe than sorry!

Here's the relevant step for discharging the CRT from an instructables on how to take apart a TV:

To discharge the CRT:
Connect one alligator connector clip to a flat-head screwdriver, and the other clip to another any screwdriver.
Push one screwdriver into the earth ground and take the other flat-head screwdriver and gently put the end under the suction-like cap. Keep pushing it in until you here a loud (or faint) "SNAP", the CRT is discharged, but push in the screw driver until you feel a little bump, the screwdriver had touched the metal clips Now the CRT is completely discharged.

posted by carsonb at 11:10 AM on May 2

Also, it's mentioned in the rest of the instructable, but don't do this without protective eyewear and the confidence that a nasty shock won't kill you. It's dangerous.
posted by carsonb at 11:13 AM on May 2

An added note: the screwdriver should have a plastic handle. Wood handles sometimes have metal butts that can be connected to the driver's shaft.
posted by Gungho at 11:28 AM on May 2

I really doubt there'd be charge remaining after seven months— but it's easy enough to discharge it and be safe.

The other danger is that if you break the tube, the resulting implosion is big enough to be pretty dangerous, what with the flying glass and all. The electron-gun end of the tube (the tapered part in back) is relatively fragile, compared to the heavily reinforced front face. So be careful with that.
posted by hattifattener at 12:02 PM on May 2

Sorry, I don't use MetaFilter much and was intemperate about the etiquette regarding wisecracks. But I was serious in the sense that messing with old electronics is more serious and dangerous than just electrical discharge. My understanding is that there might be toxic metals and even radioactive materials in some of the parts. I would go to a tv repair store and discuss it with a technician before opening up and messing with it.
posted by GhislainTwo at 12:34 PM on May 2 [1 favorite]

I think the capacitors can pick up static charge from the air, even. Being careful with grounding yourself & discharging it are good ideas.
posted by Pronoiac at 12:53 PM on May 2

Get a shell for a TV repair shop, or get the shop to un-shell yours. Those capacitors are dangerous for the untrained.
posted by orthogonality at 12:56 PM on May 2 [1 favorite]

After 7 months I'd be more worried about accidentally breaking the vacuum seal and getting hit with a shard of flying glass than about the capacitor. But I'd also wear rubber gloves and discharge it as per carsonb's instructions because I'm paranoid.
posted by TeatimeGrommit at 1:03 PM on May 2

Also note that discharging the cap instructables-style (with no resistor to limit the discharge current) is also a recipe for a potential capacitor explosion. Look on the top of the can for perforations -- that's where the exploding electrolyte is supposed to vent (aka, spray powerfully) so you don't have an even worse pipe-bomb-style pressure buildup. Sometimes the vents work, sometimes they don't. Self-charging in caps is rare but not so rare that you shouldn't treat every capacitor in every TV as fully charged.
posted by range at 1:07 PM on May 2

I took apart probably a dozen TVs for kicks as a kid with no training, safety equipment or self preservation instinct and I never had any issues with self-charged capacitors. This is not in any way to even imply that you should do any less than treat every cap like a loaded bomb and work with one hand behind your back. That's what I would do now that I know better.
posted by Skorgu at 1:59 PM on May 2

OK, you all have intimidated me out of it. I'm sort of curious about trying the grounding strategy, but I'm in an apartment in NYC, so I don't really have any ground to ground in. I could lug the thing over to Washington Square Park but then I'd be endangering others if the whole exploding thing happened. So, I will try to see if there's a local TV repair shop I can befriend.
posted by yarrow at 5:56 PM on May 2

After this much time there is little chance of any charge being left in the tv, but not no chance. You just want the shell. Take the guts out and be careful of what you touch if you are nervous. It should be pretty easy to take the guts out without touching the dangerous bits (which are probably far from dangerous at this point). I would not assume that it is safe though. So, did you see that link that carsonb posted? It is pretty good. It shows you where not to touch. Are you going to take that suction cup connector off? I didn't think so. Yes there is danger, but put it into perspective. The high voltage points are covered for a reason. Some of the rest of the capacitors and the like can also hold a charge, but not likely at more than a few days. Whenever I am going to have to manhandle electronics I pull out my multimeter, clip one lead to ground (anywhere on the metal chassis) and start probing around with the other lead to see if there are any voltages present. If you don't have one a multimeter can be had for ten or twenty bucks at Ray D. O'Shack or Home Depot. It could put you mind at ease.
posted by caddis at 7:13 PM on May 2

Before you do this, please give some thought to how you will dispose of the tube. It can implode after you have put it in the trash and possibly injure other people.
posted by yohko at 8:03 PM on May 2

Somewhat belatedly, I'd also like to add an image to give you an idea of how dangerous these things can be.

I had a friend who worked on monitors, and he claimed to know people that had had holes blown in their hands from touching the wrong thing in a TV at the wrong time.

Televisions can be unplugged for years and still carry a lethal charge in the CRT. Typical color tubes use electrons at 32,000 volts. It can take a long time for that much energy to dissipate.

Take it to a pro.
posted by Malor at 4:05 AM on May 3

OK, you all have intimidated me out of it. [....] So, I will try to see if there's a local TV repair shop I can befriend.

Well, I didn't mean to intimidate you out of it! There are some nonobvious dangers which you should be aware of, but I think with reasonable care it's not a very risky thing to do. OTOH, getting a TV repair shop to do it (and, ideally, to take the tube off your hands and dispose of it correctly) is also a fine idea.

I'm sort of curious about trying the grounding strategy, but I'm in an apartment in NYC, so I don't really have any ground to ground in.

Actually you don't need (or want) an earth ground— what this is about is shorting out the larger capacitors in the set (including the capacitance of the tube itself) to dissipate any energy they may still be storing. You want to short everything to a common, but arbitrary, potential. Confusingly, such a common potential is usually called "ground" even when it isn't the same as the earth's potential.

FWIW, a TV set of that era will have bleeder resistors designed to safely discharge the caps over time. But of course they may have failed. (Unlikely but does happen.) Even without bleeder resistors, I think they would have self-discharged after seven months. But of course maybe they didn't.

there might be toxic metals and even radioactive materials

There'll definitely be lead in the solder and lead in the glass (AIUI this is why you need to specially dispose of old CRTs instead of just putting them in the normal trash): wash your hands after handling electronics. The phosphors may have crazy rare earths in them: wash your hands, and if you do get cut by some flying glass, wash the wound thoroughly, and maybe contact poison control(?). There shouldn't be any radioactives in a TV set. OK maybe a thoriated cathode, but that'll have less radioactivity than a camping lantern or a slab of granite... additional safety tip: do not grind any parts of the TV into a fine powder and then snort them.
posted by hattifattener at 3:21 PM on May 3