-----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.
On Fri, 3 Dec 2004, Brian Densmore wrote:
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'm pretty sure its going to take a few moments of current to start melting the plastic like that. Capacitors release their energy too quick.
I haven't been able to make a capacitor uniformly melt a jacketed wire. The wires would quickly vaporize at one point, leaving the plastic intact except for a small hole. At my last job we used a capacitive discharge device called a "thumper" to locate bad cable sections. It would discharge up to 15 kilovolts from a 15uF capacitor and thump a hole in the bad section.
Just for kicks long ago, I hooked the thumper up to a 40 watt fluorescent light one time. The light appeared to lift off the ground before exploding into dust. That thing made a violent self cleaning bug zapper too.
Oh, did I mention that the wire was dancing? It was pretty cool...
I believe the seperate video inputs of his television use switching diodes to select what video is live. I believe the current shorted the diodes, so all the inputs stay on. If I remember right, these boards cost $50, but only cost $1.00 to fix. But we have a warranty in this case to keep us out of trouble.
I love post mortem troubleshooting. When things go bad, its fun to see what exactly went wrong and keep it from happening again. Sounds like they had a design flaw which they later corrected. So we may have a happy ending out of this.
I got the following e-mail reply from dell:
-----CUT---------
Thank you for contacting Dell Technical Support.
Ronnie, if I have understood it correctly, you are concerned about the smoke coming from the Laptop while trying to connect TV through TV Out connector and also the RCA cable melted because of this.
I apologize and truly regret any inconvenience this matter may have caused.
Please provide the information requested below so I can setup the service to arrange for the system to be replaced.
-----CUT-----------
This proves dell e-mail techs can't read, i posted the same story to them, word for word here, I never said the laptop smoked. I said the TV caught on fire. and the wire melted
On Fri, 2004-12-03 at 15:47 -0600, 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. _______________________________________________ Kclug mailing list Kclug@kclug.org http://kclug.org/mailman/listinfo/kclug
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. _______________________________________________ Kclug mailing list Kclug@kclug.org http://kclug.org/mailman/listinfo/kclug
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 .
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Brian Densmore -
Duane Attaway -
Oren Beck -
Thomas Bruno