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Comment by BubbleRings | Hacker News Reader

If you like playing with old hardware, be aware that old CRTs have a gotcha that can getcha: they hold a charge that can shock you across the room, and they can hold that charge for weeks or more. Google how to discharge it before poking around in a CRT.

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When I was about 12 I got an old TV in my room which I of course decided to take apart to figure out how it worked.

I was VERY smart and of course unplugged the TV before doing anything.

My flat head screwdriver brushed against the wrong terminal in the back, I was literally thrown across the room several feet, and my flat head screw driver was no longer usable as the tip had deformed and slightly melted.

I later found an electronics book that had a footnote mentioning grounding out the tube before going near it…

How does an electric shock throws someone across the room? What's the mechanism for this push?

I know a shock can paralyze (by contracting the muscles) and it can burn (by joule effect) but never seen one push

AC current paralyzes by alternately contracting and relaxing your muscles, 60 times per second. This tends to lock you in place because the electricity is a higher voltage than your nerves and overrides any command you send every 60th of a second. It could take you several minutes to die, and you will be suffering in pain and terror the whole time as you are unable to let go…

DC current jolts you “across the room“ by contracting your muscles all at once. Of course the exact effect depends on your posture; sometimes it just makes you stand upright or pull your arms in. This tends to disconnect you from the source of the electricity, limiting the damage. Note that if you cannot actually jump all the way across the room then the jolt probably can’t knock you all the way across the room either. If you fall over your head could end up pretty far away from where it started, though, and if you lose consciousness even for a little while then that can affect your perception too. It could certainly throw the screwdriver all the way across the room.

If you pay attention to the special effects that show up in movies and television you’ll soon realize that they simulate shocks by putting the actor in a harness and then pulling on it suddenly. This sudden movement away from the source of the “shock” stops looking very convincing when you notice that the movement starts at their torso rather than in their legs and arms.

I have been electrocuted twice once as a kid (which I don't remember but my parents reminded me) and once as a teenager which I definitely remember. My country's voltage was 240 volts at 50 Hz. I remember screaming uncontrollably as the current flowed through my arm and chest but managed to drop the live wire. The floor was parquet: wood.

Ouch, that is lucky.

I remember putting some keys into an electrical socket when I was quite young. My hand must have bridged live and neutral, so the current only flowed from thumb to forefinger rather than through my chest to my feet. But it was accompanied by a flash of light and an arc that I saw as a forked tongue. I told my mom that it had bitten me :)

That's fascinating, thanks for taking the time to write this

Also, what an horrifying way to die

Agreed. I’m with Quark; I want to wake up in Heaven and have no idea how I got there.

Typically it forces your leg muscles to contract as the current flows to ground and you literally kick yourself into the air.

Exact same thing happened to me as a child. I do not remember the event, but I do remember waking up on the other side of the room.

"by contracting the muscles"

Yeah the tube is essentially a large capacitor :P

I also learned electronics by shocking myself often

It's not the tube (which is just a chamber for an electron gun. It's the high voltage capacitors used to hold charge for the supply driving the electron gun.

It's the tube itself which forms the capacitor. I'm not aware of any sets that used a separate capacitor across the final anode voltage.

You either learn by shocking yourself, or die trying.

The survival selection is real in electronics.

Not just shock you across the room, but shock straight into your next life.

So we are all in post-tube life?

I have a vague recollection that my little cousin was nearly ended when he managed to destabilize the stand that a CRT was sitting on, and it fell just behind him, but I may be entirely hallucinating that memory.

Regardless, there are multiple ways old CRTs can cause great harm.

My family bought our first one and we used it keep it on a carpet floor - boy was that an electrifying experience

Same goes for your microwave.

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