Author Topic: Electric shock  (Read 18013 times)

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Offline mark3141Topic starter

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Electric shock
« on: July 03, 2013, 11:39:28 am »
IF this chap was using a voltmeter how did he come so close to killing himself?

 

Offline Rerouter

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Re: Electric shock
« Reply #1 on: July 03, 2013, 11:55:38 am »
he had it on amps....  :palm:

and his ground connection must have been poor enough that it took the few seconds to pop the fuse, with the wiring out of the device holding the voltage high enough to cling him on there,
 

Offline mark3141Topic starter

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Re: Electric shock
« Reply #2 on: July 03, 2013, 12:04:38 pm »
Hmm... yes that would do it.

He used the "moment of inattention" defence — but his seemingly random poking around mains voltages seems terrifyingly dangerous...
 

Offline BillyD

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Re: Electric shock
« Reply #3 on: July 03, 2013, 12:18:35 pm »
Shouldn't be wearing metal jewellery around live electrics either.

 

jucole

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Re: Electric shock
« Reply #4 on: July 03, 2013, 12:25:00 pm »
Poor chap! I'm not sure he knows himself what setting he had his meter on, but there's a nice MOS 6502 in what looks to be a commodore floppy drive though.
 

Offline Rerouter

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Re: Electric shock
« Reply #5 on: July 03, 2013, 12:57:32 pm »
if anything this may make him respect mains a bit more, i for one never work live unless its the only possible way, and when i do need to, keep on a non conductive mat with one hand in a pocket or a glove, cause once it bites, its got you and your not moving,

also i seriously have to wonder why it took so long for his fuse to pop, the meter measures across what 0.1 ohm? plus another 1.5 for both meter leads, that leaves about another 20 ohms unaccounted for... that or it was grossly over-rated or self wound with wrong wire, considering he doesn't have ground fault current interrupters or residual current detecting outlets it would put the house in that vintage
 

Offline mark3141Topic starter

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Re: Electric shock
« Reply #6 on: July 03, 2013, 01:24:57 pm »
Has Dave ever posted a piece on safety — along the lines of "Really stupid things to avoid doing at all costs"?

To prevent my last mistake becoming my final mistake.
Might be an idea...
 

Offline Rufus

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Re: Electric shock
« Reply #7 on: July 03, 2013, 02:21:37 pm »
he had it on amps....  :palm:

Not much makes sense in the video.  This looks like a service manual for what he was playing with

http://wiki.classic-computing.de/images/0/07/1540%2B1541_SERVICE-MANUAL.pdf

The plug he poked the meter probes into has two secondaries from the transformer - no mains.

The chassis appears to be a single folded metal sheet so there is no way he would be shocked by holding onto either side of it.

IMO either he has given an extremely poor depiction of what he actually did or it is just made up bullshit.

 

BulletMagnet83

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Re: Electric shock
« Reply #8 on: July 03, 2013, 08:13:46 pm »
Having cocked up quite a few times and touched something I shouldn't as an electrician's mate a good few years ago, part of me doesn't believe what he said he did could have had the effect reported. I'm not, and most likely never will be, an expert.... but I've had enough shocks to know that if there's a properly-working RCD on that circuit, you get a jiggle and say a few naughty words then the supply gets knocked out and everyone has a good laugh about it on teabreak.

I also doubt the muscle lock-up thing... for AC anyway (I always thought it was HVDC that did that, though I welcome any corrections!). Again only going on my own experience, a mains AC shock felt like intense vibration together with something like a cross between a nettle sting and hitting your funny bone, then jerking away from it. Not something I'd do on purpose, but with functioning RCDs/RCBOs on the line, not the end of the world and certainly not video-worthy.

That said, I do love my retro computing porn, so have subscribed to the chap's channel anyway! :D

EDIT: In case it sounded too much like I was making light of a potentially serious hazard, I did (eventually) learn, and get some proper 1kv insulated gloves for work that required things to be tested live.
« Last Edit: July 03, 2013, 08:15:40 pm by BulletMagnet83 »
 

Offline c4757p

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Re: Electric shock
« Reply #9 on: July 03, 2013, 08:28:28 pm »
He's bullshitting. No way that plug has mains on it, and apparently he didn't get shocked until he had *both* hands on the same shielding plate?  :blah:
« Last Edit: July 03, 2013, 08:34:40 pm by c4757p »
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Offline david77

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Re: Electric shock
« Reply #10 on: July 03, 2013, 08:30:27 pm »
he had it on amps....  :palm:

Not much makes sense in the video.  This looks like a service manual for what he was playing with

http://wiki.classic-computing.de/images/0/07/1540%2B1541_SERVICE-MANUAL.pdf

The plug he poked the meter probes into has two secondaries from the transformer - no mains.

The chassis appears to be a single folded metal sheet so there is no way he would be shocked by holding onto either side of it.

IMO either he has given an extremely poor depiction of what he actually did or it is just made up bullshit.

This.

That guy hasn't got a clue what he's talking about.
 

Offline millerb

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Re: Electric shock
« Reply #11 on: July 03, 2013, 08:32:48 pm »
I got the worst shock of my life working on a neon sign. I was holding the metal bars that prop up the tube structures with my left hand while screwing with some connecting wires with my right hand... The transformer was putting out 8,000V AC. I couldn't let go of the damn thing even though I tried with all I had. What saved me was falling backwards out of my chair. I'd probably be dead if I fell over on to it. AC can definitely lock up your muscles.
 

Offline c4757p

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Re: Electric shock
« Reply #12 on: July 03, 2013, 08:33:17 pm »
A thought: would this thing have filter caps mains-earth? Perhaps for some reason during his probably very unintelligent jaunt through its internals, he disconnected the earth. Then he got a little nip out of the filter cap and he's exaggerating the hell out of it.
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BulletMagnet83

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Re: Electric shock
« Reply #13 on: July 03, 2013, 08:36:33 pm »
A thought: would this thing have filter caps mains-earth? Perhaps for some reason during his probably very unintelligent jaunt through its internals, he disconnected the earth. Then he got a little nip out of the filter cap and he's exaggerating the hell out of it.

If so, he should probably never play with any disposable cameras, he'd probably piss his pants.

Millerb, yeah I bet!  :o 8000VAC is something I hope to never experience, and I have no trouble believing that WOULD lock up your muscles... I just reckon 230VAC normally wouldn't, especially with some fault protection on the circuit.
« Last Edit: July 03, 2013, 08:40:52 pm by BulletMagnet83 »
 

Offline c4757p

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Re: Electric shock
« Reply #14 on: July 03, 2013, 08:39:21 pm »
They're fun, aren't they? That was my first electric shock ever  ;D

Didn't he say something about an earth lead being available when he was working on it? I think he did disconnect it...
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BulletMagnet83

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Re: Electric shock
« Reply #15 on: July 03, 2013, 08:42:56 pm »
Haha yes, they are fun. My first teardown was a flash camera aged <10, and guess who didn't discharge it before handling the board? Still, playing with those, and cap discharge pyro igniter circuits based on them, taught me one valuable lesson - never EVER give in to temptation and buy huge 4kV pulse discharge caps from eBay... no way I can be trusted with them! A 2J discharge hurts more than enough.
 

Offline c4757p

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Re: Electric shock
« Reply #16 on: July 03, 2013, 08:47:41 pm »
I'm too much of a pansy with high energy stuff. I wouldn't go near them lest they become demon-possessed, go crazy and bite me. HV by itself doesn't bother me, but the capacitors that are measured in the volume of shit you lose if you accidentally discharge one are not something I'm fond of.
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BulletMagnet83

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Re: Electric shock
« Reply #17 on: July 03, 2013, 08:54:35 pm »
Yeah, that's one area I'm more than happy to watch on Youtube rather than attempt myself. Still, I think it's fair to say most shocks I've had, I've been able to laugh about afterwards... That makes me feel lucky though, rather than complacent. Small mistakes we can walk away from serve to make us better in the long run :)
 

Offline G7PSK

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Re: Electric shock
« Reply #18 on: July 03, 2013, 09:07:48 pm »
I had a shock from an 1980's 22 inch colour TV HT. It knocked me across the room and 9000 volts from a mains powered cattle fence energizer, straight from the terminals lifted me off my feet, both times it felt as though all the bones had been pulled from my arm and then snapped back.
 

Offline c4757p

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Re: Electric shock
« Reply #19 on: July 03, 2013, 09:13:58 pm »
The worst I've had was ~600VDC out of an oscilloscope. Came pretty close to giving myself a good one off a CRT flyback transformer, though - I was playing around with a CRT, trying to get it to work, and must have been touching something without realizing it had HV on it. Luckily it was shut off by the time I touched my oscilloscope and discharged into the BNC. I had quite a bit of charge built up on me... :-DD
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Offline ptricks

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Re: Electric shock
« Reply #20 on: July 03, 2013, 10:03:17 pm »
I have gotten shocked by AC and DC, DC took longer for the pain to go away. I started my career when CRT TV were the best tech  and that meant working with the giant capacitors that are CRT , they can remain charged for years after last use.  The worst part was that on most sets everything inside the case was live, even touching something like the wires to the speaker could give you a shock. Most sets produced  165VDC for the boards main supply. 
 

Offline orbiter

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Re: Electric shock
« Reply #21 on: July 03, 2013, 11:14:51 pm »
@ 4:20 he mentions that he couldn't let go of the device because it was running on AC. He then states
that 'once AC has got you, It's got you and you have to be pushed off it'! :palm:
 

duskglow

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Re: Electric shock
« Reply #22 on: July 03, 2013, 11:19:53 pm »
Those live chassis televisions were awful.  I still am surprised I never really got shocked.  I must have been remarkably paranoid for a ten year old.   :palm:
 

Offline IanB

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Re: Electric shock
« Reply #23 on: July 03, 2013, 11:40:11 pm »
Carpet doesn't conduct electricity. So you could poke something through the grille and touch a live part and most likely you wouldn't feel a thing...
 

Offline cthree

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Re: Electric shock
« Reply #24 on: July 04, 2013, 12:07:00 am »
My worst shock was from a telephone patch panel. The shock was getting a shock from a phone line, the pain was intense, like a hundred bees stringing me in the finger all at once. I must have touched 48VDC ringer voltage. No buzz like with AC.

I've been zapped with AC mains many times. They say you can't let go? Bullshit! You touch a live mains hot wire and you'll yank your hands out of there real quick! It happens all the time and very few people suffer any lasting effects. There aren't enough ambulances.

That said, play safe!
 


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