6 ms·

> It's also a safety issue, since the Cathode voltage might be substantial. When I was a small kid, my father had a TV set repair side hustle. I was 7-8yo but

> It's also a safety issue, since the Cathode voltage might be substantial. When I was a small kid, my father had a TV set repair side hustle. I was 7-8yo but I would sometimes be called to help him a bit. Once he asked me to clean a bunch of CRT tubes from substantial amount of dust. What he forgot is that he was just testing one of them and the charge wasn't properly dissipated and it did not have time to dissipate on its own. I got hit with a spark so powerful, that it must have temporarily disrupted my brain because for a brief moment I was completely stupefied, and then I just resumed cleaning it. Then I got hit for the second time, then for the third time. Only after third time I realised that me cleaning the tube has something to do with it. Probably the discharge was much less powerful the third time and did not stun me completely. I can tell you the voltage and amount of charge on these things is no joke. Multiple tens of thousands of volts is enough to stun you temporarily. Probably not enough to cause lasting damage unless you are extremely unlucky about where the discharge went (stun guns usually have higher voltage and capacity), but enough for you to lose control of your body, fall and hurt yourself.

colechristensen 3y ago
>Probably not enough to cause lasting damage unless you are extremely unlucky about where the discharge went You don't have to be that unlucky. Discharge across your heart can stop it, no problem. It is not at all difficult for that energy to route through your chest. You were lucky.
- onetimeuse92304 3y ago
  Well... one difference between a stun gun and CRT tube is that in a stun gun you usually have both terminals relatively close to each other. Little chance of the main pulse going deep across the chest. On the other hand working with the CRT you are likely using both hands and that makes the signal go through your upper chest, by default. So yeah, there is something to it. One thing I learned as amateur EE is to always use just one hand to probe the device under test if there is any high voltage or AC involved. You put the other hand behind you so that there is no chance you create a short right through your chest.
  - Scoundreller 3y ago
    And have someone nearby with a 2x4 to beat you off whatever you might be gripping/fell onto.
    - sowbug 3y ago
      Just to add a bit more color here: most flexor muscles in your body are a lot stronger than the corresponding extensors, so when an external command comes in telling both to contract, for example from electricity in the thing you're working on, gripping wins. You can't let go. Great for grabbing a branch as you fall out of a tree. Not so great for repairing a power line. Late edit: I've heard you can use this factoid to your advantage to avoid being eaten by an alligator or crocodile. Wrap your arms around its snout and hold on for dear life. Their jaws are strong enough to snap you in two, but not enough to force themselves open when you're holding them shut. I don't know what Step Two is, unfortunately.
      - jareklupinski 3y ago
        > I don't know what Step Two is, unfortunately. step two is waiting for the aforementioned 2x4 wielder "to beat ... whatever you might be gripping/fell onto"
        rzzzt 3y ago
        "Mother" on speed dial maybe?
      - hallway_monitor 3y ago
        The bit about holding an alligator's mouth closed is correct and I remember Step Two from an alligator wrestling demonstration: flip it over. They lose consciousness if you can hold them in an inverted position.
        HeyLaughingBoy 3y ago
        So do chickens, but they're a lot easier to wrestle.
- Cthulhu_ 3y ago
  That said, direct current is "safer" than alternating current; AC makes your muscles (and heart) spasm/contract 50 or 60 times a second like it's fibrilating, DC locks everything up like a defibrilator. I recommend neither though.
  - Zardoz84 3y ago
    high frequency alternate current is the safest, in the sense that the skin effect enters in effect, and the current doesn't touch your muscles (or at least your hearth). However, the danger of burns persists.
    - dfox 3y ago
      The nasty thing about HF burns is that you often do not notice that something is wrong until you either smell the burnt skin or the burn starts to deep enough to become acutely painful. It is perfectly possible to burn 1mm dia hole completely through you thumb and nail by inadvertly placing your thumb over output connector of CCFL inverter without you noticing that this is happening.
- kloch 3y ago
  > Discharge across your heart can stop it, no problem. It is not at all difficult for that energy to route through your chest. You were lucky. As my dad used to say "It's volts that jolts, but mills that kills!" (you can survive a jolt very large voltage, but only a few milliamps across the heart can kill you)
- deleted 3y ago
  [deleted]
- ryanjshaw 3y ago
  Not just heart-stopping-dangers! I had a dishwasher whose wiring was damaged by a rat. I unplugged the dishwasher, and started working on the wires - maybe 1mm thickness. Next thing I know, I've punched myself in the face and knocked myself to the floor from something discharging, and need an ice pack on my lip.
  - QuercusMax 3y ago
    I had a dishwasher whose wiring wasn't installed properly, and it eventually caught fire. Seeing smoke and flames come out of a running dishwasher is something I won't soon forget!
- LorenPechtel 3y ago
  But that takes current, not merely voltage. It's very hard to do with the discharge of static energy.
- userbinator 3y ago
  Stopping the heart is no problem --- that's what defibrillators do, after all! The heart stops, and then starts again with all its muscles in sync. The problem is when the shock is not enough to stop the heart but causes it to lose sync and go into fibrillation.
orbital-decay 3y ago
I also touched a CRT anode when fiddling with a TV set when I was 12. I was aware of the danger and scared of that thing (it was huge!) but still forgot to discharge it. Despite the ~26kV nominal voltage there was only enough charge to make me jump to the ceiling, or at least I thought so. It's a lesson you never forget.
deleted 3y ago
[deleted]
LorenPechtel 3y ago
I got zapped once as a kid. My grandfather's TV, I was pulling the tubes to take them to the testing machine. Fairly small screen but I knew it probably had some residual charge that I most definitely didn't want to come into contact with. The layout was such that I could pull the tubes while staying far away from it. It never occurred to me that safety would require keeping him from looking on in curiosity and bumping my arm. (He was impatient about getting his TV fixed, I saw that whoever designed it had had the courtesy to put the tubes in an area where even if your hand slipped it wouldn't approach the tube. That was no protection against my hand getting moved in a direction I was not applying force, though.) I don't think such things are actually capable of direct lasting damage but you do lose control--I slammed my hand into the cabinet pretty hard, completely involuntary. My understanding is that tasers are AC, thus involuntary movements will be back and forth rather than just in one direction.
- bb611 3y ago
  > My understanding is that tasers are AC, thus involuntary movements will be back and forth rather than just in one direction. Tasers AC output is at low frequency but still significantly faster than human muscles can move, if you watch any video of a tase you'll see it causes the victim's muscles to seize up and not oscillate.
lttlrck 3y ago
I was thrown across a room twatting around in the back of a TV. Many years later I still wonder if there were any sdiefeftcs.
- rokkitmensch 3y ago
  "I don't hire programmers who spell correctly, I hire programmers who misspell consistently" or how does it go

colechristensen 3y ago

>Probably not enough to cause lasting damage unless you are extremely unlucky about where the discharge went You don't have to be that unlucky. Discharge across your heart can stop it, no problem. It is not at all difficult for that energy to route through your chest. You were lucky.

onetimeuse92304 3y ago
Well... one difference between a stun gun and CRT tube is that in a stun gun you usually have both terminals relatively close to each other. Little chance of the main pulse going deep across the chest. On the other hand working with the CRT you are likely using both hands and that makes the signal go through your upper chest, by default. So yeah, there is something to it. One thing I learned as amateur EE is to always use just one hand to probe the device under test if there is any high voltage or AC involved. You put the other hand behind you so that there is no chance you create a short right through your chest.
- Scoundreller 3y ago
  And have someone nearby with a 2x4 to beat you off whatever you might be gripping/fell onto.
  - sowbug 3y ago
    Just to add a bit more color here: most flexor muscles in your body are a lot stronger than the corresponding extensors, so when an external command comes in telling both to contract, for example from electricity in the thing you're working on, gripping wins. You can't let go. Great for grabbing a branch as you fall out of a tree. Not so great for repairing a power line. Late edit: I've heard you can use this factoid to your advantage to avoid being eaten by an alligator or crocodile. Wrap your arms around its snout and hold on for dear life. Their jaws are strong enough to snap you in two, but not enough to force themselves open when you're holding them shut. I don't know what Step Two is, unfortunately.
    - jareklupinski 3y ago
      > I don't know what Step Two is, unfortunately. step two is waiting for the aforementioned 2x4 wielder "to beat ... whatever you might be gripping/fell onto"
      - rzzzt 3y ago
        "Mother" on speed dial maybe?
    - hallway_monitor 3y ago
      The bit about holding an alligator's mouth closed is correct and I remember Step Two from an alligator wrestling demonstration: flip it over. They lose consciousness if you can hold them in an inverted position.
      - HeyLaughingBoy 3y ago
        So do chickens, but they're a lot easier to wrestle.
Cthulhu_ 3y ago
That said, direct current is "safer" than alternating current; AC makes your muscles (and heart) spasm/contract 50 or 60 times a second like it's fibrilating, DC locks everything up like a defibrilator. I recommend neither though.
- Zardoz84 3y ago
  high frequency alternate current is the safest, in the sense that the skin effect enters in effect, and the current doesn't touch your muscles (or at least your hearth). However, the danger of burns persists.
  - dfox 3y ago
    The nasty thing about HF burns is that you often do not notice that something is wrong until you either smell the burnt skin or the burn starts to deep enough to become acutely painful. It is perfectly possible to burn 1mm dia hole completely through you thumb and nail by inadvertly placing your thumb over output connector of CCFL inverter without you noticing that this is happening.
kloch 3y ago
> Discharge across your heart can stop it, no problem. It is not at all difficult for that energy to route through your chest. You were lucky. As my dad used to say "It's volts that jolts, but mills that kills!" (you can survive a jolt very large voltage, but only a few milliamps across the heart can kill you)
deleted 3y ago
[deleted]
ryanjshaw 3y ago
Not just heart-stopping-dangers! I had a dishwasher whose wiring was damaged by a rat. I unplugged the dishwasher, and started working on the wires - maybe 1mm thickness. Next thing I know, I've punched myself in the face and knocked myself to the floor from something discharging, and need an ice pack on my lip.
- QuercusMax 3y ago
  I had a dishwasher whose wiring wasn't installed properly, and it eventually caught fire. Seeing smoke and flames come out of a running dishwasher is something I won't soon forget!
LorenPechtel 3y ago
But that takes current, not merely voltage. It's very hard to do with the discharge of static energy.
userbinator 3y ago
Stopping the heart is no problem --- that's what defibrillators do, after all! The heart stops, and then starts again with all its muscles in sync. The problem is when the shock is not enough to stop the heart but causes it to lose sync and go into fibrillation.

orbital-decay 3y ago

I also touched a CRT anode when fiddling with a TV set when I was 12. I was aware of the danger and scared of that thing (it was huge!) but still forgot to discharge it. Despite the ~26kV nominal voltage there was only enough charge to make me jump to the ceiling, or at least I thought so. It's a lesson you never forget.

deleted 3y ago

[deleted]

LorenPechtel 3y ago

I got zapped once as a kid. My grandfather's TV, I was pulling the tubes to take them to the testing machine. Fairly small screen but I knew it probably had some residual charge that I most definitely didn't want to come into contact with. The layout was such that I could pull the tubes while staying far away from it. It never occurred to me that safety would require keeping him from looking on in curiosity and bumping my arm. (He was impatient about getting his TV fixed, I saw that whoever designed it had had the courtesy to put the tubes in an area where even if your hand slipped it wouldn't approach the tube. That was no protection against my hand getting moved in a direction I was not applying force, though.) I don't think such things are actually capable of direct lasting damage but you do lose control--I slammed my hand into the cabinet pretty hard, completely involuntary. My understanding is that tasers are AC, thus involuntary movements will be back and forth rather than just in one direction.

bb611 3y ago
> My understanding is that tasers are AC, thus involuntary movements will be back and forth rather than just in one direction. Tasers AC output is at low frequency but still significantly faster than human muscles can move, if you watch any video of a tase you'll see it causes the victim's muscles to seize up and not oscillate.

lttlrck 3y ago

I was thrown across a room twatting around in the back of a TV. Many years later I still wonder if there were any sdiefeftcs.

rokkitmensch 3y ago
"I don't hire programmers who spell correctly, I hire programmers who misspell consistently" or how does it go