3 ms·

I did it by sticking a screwdriver where I shouldn't have and touching the flyback cap on an old (CRT) TV that was only recently unplugged. Luckily I wasn't wel

I did it by sticking a screwdriver where I shouldn't have and touching the flyback cap on an old (CRT) TV that was only recently unplugged. Luckily I wasn't well-grounded and the part of the screwdriver shunted the current turned to slag.

tgsovlerkhgsel 6y ago
Did you get shocked at all? I'm trying to understand what the return path for the current would be in this situation.
- throwanem 6y ago
  Through the screwdriver shank, as it's placed across the capacitor terminals. This creates a dead short through which the differing potentials on the capacitor plates can equalize - and if the capacitor is large enough, they do so quite enthusiastically. I ruined a screwdriver of my own that way once, discharging a photoflash cap in a flash head whose control circuit had died with the cap at full charge. Didn't do my hearing any good, either, I'm sure - it took fully half an hour for the ringing to go away.
JJMcJ 6y ago
TV repair shops use a special tool to discharge those caps, basically a high voltage rated resistor pack. Largely a disappeared skill. I believe if you are really lucky if you discharge with a screwdriver, the cap can explode, not just melt the screwdriver. Same with batteries, like auto batteries, extra points there with boiling acid and hunks of thick plastic flying around.
- bigiain 6y ago
  Pretty sure a car battery (at least the old school 12V lead acid type) wont explode from a short. I welded a spanner onto the terminals of one once by clumsily dropping it and having it land across the terminals. Now I have to go look on youtube, to see if anyone's filmed themselves dropping a spanner across a Tesla's battery...
  - pnutjam 6y ago
    Growing up, my dad had a shirt with acid holes. My mother said he blew up a battery while working on it. My dad was a DYI guy, but didn't regularly work around anything caustic. This would have been early 1980's.
    - bigiain 6y ago
      I have seen car batteries explode, always due to bad charging rather than shorting though. (Over charging generates hydrogen and oxygen inside the battery in precisely the correct stoichiometric ratio to go "BOOM!") (I also had a friend wake up to about $500 worth of dead tropical fish, the morning after plugging a charger and car battery in on the shelf under his tank. Not entirely sure what the mechanism was, but the pH in the tank dropped enough to kill all the fish. )

tgsovlerkhgsel 6y ago

Did you get shocked at all? I'm trying to understand what the return path for the current would be in this situation.

throwanem 6y ago
Through the screwdriver shank, as it's placed across the capacitor terminals. This creates a dead short through which the differing potentials on the capacitor plates can equalize - and if the capacitor is large enough, they do so quite enthusiastically. I ruined a screwdriver of my own that way once, discharging a photoflash cap in a flash head whose control circuit had died with the cap at full charge. Didn't do my hearing any good, either, I'm sure - it took fully half an hour for the ringing to go away.

JJMcJ 6y ago

TV repair shops use a special tool to discharge those caps, basically a high voltage rated resistor pack. Largely a disappeared skill. I believe if you are really lucky if you discharge with a screwdriver, the cap can explode, not just melt the screwdriver. Same with batteries, like auto batteries, extra points there with boiling acid and hunks of thick plastic flying around.

bigiain 6y ago
Pretty sure a car battery (at least the old school 12V lead acid type) wont explode from a short. I welded a spanner onto the terminals of one once by clumsily dropping it and having it land across the terminals. Now I have to go look on youtube, to see if anyone's filmed themselves dropping a spanner across a Tesla's battery...
- pnutjam 6y ago
  Growing up, my dad had a shirt with acid holes. My mother said he blew up a battery while working on it. My dad was a DYI guy, but didn't regularly work around anything caustic. This would have been early 1980's.
  - bigiain 6y ago
    I have seen car batteries explode, always due to bad charging rather than shorting though. (Over charging generates hydrogen and oxygen inside the battery in precisely the correct stoichiometric ratio to go "BOOM!") (I also had a friend wake up to about $500 worth of dead tropical fish, the morning after plugging a charger and car battery in on the shelf under his tank. Not entirely sure what the mechanism was, but the pH in the tank dropped enough to kill all the fish. )