Macintoshguy1984
Well-known member
Whenever i open a macintosh up with a crt, I get this feeling that I might get shocked from the crt. Does anyone know the chances of getting shocked?
I discharged a Commodore PET's monitor's CRT once using an ad-hoc tool consisting of a screwdriver grounded by heavy-gauge wire to a cold water pipe, and even though the shock didn't go *through* me the hand holding the screwdriver felt a distinct slightly-painful *tingle* when I made contact. I can totally imagine that the unfiltered experience must hurt like *ell. One correction, though:But let me say this - for being stupid and rushing the job, I have been shocked by that Mac CRT a dozen or so times. Thing is, it did not go through my heart. It went through my hand, up my arm and out what ever my arm was touching, so I was lucky. BUT, IF FREAKING HURT LIKE HADES!!!! it feels like your fingers were blown off as the nerves yell at you for the next 1/2 hour "YOU IDIOT!!!" But like I said, the shock did not go through my heart. That would have done me in. And I'm still here to post this.
Technically a shock *doesn't* have to "pass through your heart", a sufficiently large shock that transits *anywhere* in the central nervous system can cause irregular hearbeat and/or breathing disruption. Also, technically speaking, it's *mostly* the Amps that kill you, not the volts, and as little as 100ma at any voltage *properly applied* could kill you. What makes higher voltages generally more dangerous is they're more likely to overcome the resistance your body presents between source and ground. (Your body isn't a *particularly* good conductor so, for instance, there's a pretty good chance you'll get away totally unscathed by brushing dry fingers across both poles of a 12v car battery despite the potential for a positively massive jolt of amps therein, while the voltages you'll find in a flyback transformer are sufficiently high that it's possible that a spark could hop to you *across dry air* under the right/wrong circumstances.) If you've ever licked the top of a 9v transistor radio battery you'll know that it's *possible* to get a nice painful shock from even piddly low voltages if you overcome that whole resistance thing.I Bolded that "THROUGH YOUR HEART" because in order for any electrical shock to kill you, it has to go through your heart, a minimum of 12V at 4 AMPs will do it. At 5V, it can be 6amps to kill you. At 10KV, I forget but 1/2 an amp will do you in.
That would be my bad, but in my defense the site I googled up for instructions on how to do it gave me the bad information.Connecting one end to a cold water pipe is not guaranteed to work, and is unnecessary in any case. All you want to do is to short out the capacitor, and that means providing a conductive path between its two terminals. No need to take the long way around! And the cold water pipe wouldn't work if the Mac isn't plugged into the wall
Or, if you do, you are also implicitly specifying the resistance of the circuit. R=V/I - "Ya canna' violate the laws of physics, cap'n!" Lt. Cmdr Montgomery Scott.You simply cannot specify both current and voltage independently.
I think it depends on who "you" is, and how unlucky you are. Sometimes people have heart conditions that they don't know about.The charge stored in a 9" crt is far too small to do you in.