Instructables

Step 3: The dangerous part...

Now, this is the dangerous part, discharging the CRT...
Why should you do this? Because the CRT acts like a high voltage capacitor and it can hold a lethal charge. The charge stored in the CRT can last a very long time, usually a few months, sometimes for a few years...

So it is important to safely discharge the CRT before you do anything else - otherwise you might end up in the grave...

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.

Now, simply cut the HV wire off near the suction-like cap.
I took the suction-like cap off completely because I know how to do it. Taking the suction-like cap off the CRT can be tricky and dangerous.
 
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i talked with a tv repair person and they said that a screwdriver can't handle 10,000 volts.he says that you should use a high voltage probe connected to a 1mega ohm half watt resistor just to be safe. here is a pic of the probe.
PR-28A.jpg
Plasmana (author)  devicemodder5 years ago
That is true, screwdrivers, cannot handle 10Kv, however, the screwdriver is grounded, so it is 0v.

Screwdriver will be fine. Your safety, however, depends on how thick the plastic mold around the one you're touching is though. Like these other guys says, current is the issue. However, even with a large current, in this situation, the current flow will last half an instant, not even long enough to break a low current fuse, given the chance. Don't worry about what "professionals" use. Use what you have; screwdrivers are bound to have some resistance anyway, depending on the metal. If you want to feel safe, buy a random resistor >100Kohm (at least 1/4 watt) and splice it in series with whatever you have going on. Like I said before, even if the power is measured over that, it's pretty instantaneous, so your resistor won't burn out (similar to the fuse idea).

The screwdriver isn't 0V, and technically, neither is ground. Ground is only a reference point. A voltage is the potential difference between two points, and ground is simply used as the lower of the two terms in the difference equation.

The screwdrivers + alligator clip + wire are at ground voltage before touching the high voltage wire. When one of the screwdrivers touches the HV wire however, there will be a potential difference of +10-20kV across the screwdrivers + Alligator clip + wire with respect to the ground voltage. This will mean that a current will flow through them (a VERY high current). It's the current that will damage the screwdrivers, not the voltage. An increase in voltage will produce an increase the current.
Also, although it won't be much of a risk if you have a good ground connection, make sure that the screwdriver you're using has a good deal of insulation on the handle. Do NOT use those micro screwdrivers with metal handles. If you have already however and are still with the living, it is because the resistance of your body is MUCH greater than the resistance in the wire connection the screwdriver to ground. Electricity takes the path of least resistance (well, current will still flow through all paths, but will be inversely proportional to their resistances)
It may be 10,000V, but the the transient time is so small that a screwdriver will suffice. You might also notice that he used tiny multi-core wire to connect between the two screwdrivers. If the voltage was constant, the wire would act like a fuse and melt almost instantaneously, but the time that it takes to discharge the CRT will likely be in the low milliseconds, so this isn't a problem.
I attempted to discharge the CRT but no sound was made. How am i supposed to know if it is discharged or not?

It probably is. Usually if you leave it sit around an hour it'll be discharged anyway. However, what I have done before is take some large branch trimmers (like pictured) with as insulated handles as possible and cut the high voltage wire. Then I carefully drove the tip of the wire into the ground. 1000V usually requires an insulation thickness of about a quarter to a half of a centimeter.
First time I tried messing with a CRT I didn't realize the capacitance potential of these and flat out made my heart skip a beat (>6kV). Not fun, but I wasn't grounded so I was relatively okay.

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peckert3 years ago
I have a really small TV (the ones which can be operated by batteries). I just want to place it in a different case (together with an old pong clone) to make a pong-station out of it.
If i discharge the tube, for safety reasons, as you described here, will it still work after putting it then in a differnt housing? I don't wanna break it.
hidgee4 years ago
I have a tv that is REALLY old, like I want to say from the fifties if not even earlier, I want to take it apart, does the crt last that long? What if it's already broken inside? I have it in my house, can I ground it while inside or will I need to take it outside?
Plasmana (author)  hidgee4 years ago
How will I know if its broken or not? I am not telepathic with stuff.. :P Anyway, be very careful when you take apart an old TV, the CRT is very fragile compared to the modern day CRT's. I had one that implode right nest to me after accidentally hitting it with a bike when I was a kid, luckily, I wasn't scarred. :)
BFeely5 years ago
In the second picture you can clearly see metal straps on the CRT tube. That is what you want to wire your screwdriver into before poking it under the suction cup, because those straps ground the tube.
Plasmana (author)  BFeely5 years ago
You mean those straps are the ground of the TV?
BFeely Plasmana5 years ago
They are the ground straps of the CRT itself.  Grounding to these straps ensures that the CRT is safely discharged, and eliminates the possibility of frying the electronics.
insistent5 years ago
What happen if i do it when the ground is wet? Because its raining everyday in quebec this years.
And what if i plug it to a metallic chair?
Plasmana (author)  insistent5 years ago
?
I mean, remove the screwdriver and plug the alligator on a metalic chair
Plasmana (author)  insistent5 years ago
As long as the metal chair is connected to the earth gound. :-)
And the plastic-like scredriver on you picture that is on the ground, is it safe if i use this material? I kinda think that the static will pass thru the plastic then me.
Ok lol, i was about to do it with a cheap metallic chair.
Plasmana (author)  insistent5 years ago
That is not a problem, just make sure you do it while it is not raining.
You used a screwdriver connected to ground by pushing it into the soil but wouldn't that mean that u had to connect the ground pin of the plug to the soil??
helennnnn5 years ago
I actually winged the disassembling. This was before i knew taking apart a television was so dangerous. For some reason nothing happened to me when i just used a pair of scissors to cut the suction cap. Luck?