TV-OUT on laptop causes major damage, fire / shock

[Oren Beck]

Brian Densmore wrote:
>>-----Original Message-----
>>From: Duane Attaway
>>
>>OK, I recreated the laptop video out to television experiment.
> 
> Dude! You are seriously twisted. ;')
> 
> 
>>The first video was connecting the RCA cable to house 
>>current.  It was 
>>uneventful and promptly blew the 20A house breaker each time.  So I 
>>started up the generator and was able to use unfused power.
>>
>>Here is a frame by frame of the video of the outer (ground) 
>>conductor of 
>>the video cable melting under 120 volts at 7500 VA:
>>
>>http://dattaway.org/whitewire.jpg
>>
>>Closeup of melted RCA cable:
>>
>>http://dattaway.org/whitewire2.jpg
>>
>>Other side:
>>
>>http://dattaway.org/whitewire3.jpg
>>
>>It took about two seconds of short current to melt the wire 
>>and break the 
>>circuit.  It flashed when it broke.
>>
>>So what does that mean?  It takes a lot of current from a 120 
>>volt feed to 
>>blow the tiny stranded wires of a RCA video cable.  I believe 
>>each one of 
>>the copper strands alone, seperated in air, should take 5 
>>amps each.  I 
>>counted 15 strands.
>>
>>Could a capacitor do it as someone suggested?  Well it could, 
>>but it would 
>>have to be instantaneous.  I have some capacitors up to 8KV 
>>if you want to 
>>see more video and pictures.
> 
> Well it depends on the type of capacitor. It would have to be 
> a polarized capacitor. I remember when I used to test power 
> supplies for a company I worked at. We would buy them for
> our products, but they needed to be tested before being installed in
> our equipment. Every once in a while a PS would have the capacitor in
> reverse polarity. Quite a show when a big capacitor blows.
> Less frequently the capacitor would take too much voltage with 
> the same end result, explosion. why do you say it would have to
> be instantaneous? Although from the description of the event it was 
> instantaneous.
> 
> 
>>I'd say his power supply had a minor meltdown inside, causing 
>>the AC to 
>>couple with the DC side.  This allowed current to flow from 
>>the AC mains, 
>>through his laptop, and return through the television back 
>>into the wall. 
>>Televisions are designed with a neutral grounded chassis and 
>>this may have 
>>allowed a possibly defective power supply to complete a current loop.
> 
> I'd tend to agree he's got a current/voltage leak in the PS, which
> of course could lead to a capacitor explosion. Haven't heard whether
> the laptop is usable now or if the adaptor is usable. If a cap went the PC
> or adaptor wouldn't work anymore. He's lucky the TV still works.
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> 
Another possible fault path is the isolation in the tv . MANY modern sets
have what is called a " Hot/Cold" chassis where parts are "isolated" from
  earth ground and could explain odd current effects .  All it takes is 
a ground
  foil to break and the broken end to touch the wrong trace and POOFT ...
This coming from having spent several years fixing tv sets to component
  level when one could still make $ at it . Now that sets are almost 
considered
  throwaway the construction has only gotten scarier . Take a good voltmeter
  and see if there is voltage from the tv video jack to earth ground- be 
careful
of course .

A longer shot is reversed hot and neutral in one outlet of  either the 
tv or computer?
Still longer shot is outlet #1  that tv is in is on L1 of a 220 service 
and outlet#2
that laptop was plugged in was on L2 AND  neutral/ground was reversed 
causing
220 volt potential difference ? The "hot" from one outlet thus tied to 
the chassis of
tv, and the "hot" of the other leg tied likewise so both supposed 
grounds were hots
of opposing legs = your arc current .

Oren

Thus what SHOULD  have been ground/neutral was HOT and POP goes your 
weasel .
   Again this is guesswork but supported by past barking frog incidents 
of similar  causes .
Headphone jacks on some tv's were potentially deadly if used where one 
could be grounded
and the isolation cap failed .  No reported deaths  but many near misses .