HDTV Melted Wires

[Alklazaris]

I heard a short circuit and saw smoke. I disconnected it and let it sit for months till I decided to fix it myself. Inside I found 2 sets of hot and neutral wires that had the insulation burned to a powder. The bare wires touched the metal mounting plate and created some sort of corrosion in the process or perhaps its the remains of the insulation. The wires seem to lead from a main circuit in the middle, to some sort of RAM or GPU circuit board. It has 2 rows of rectangular chips running the down the circuit board.

Questions:
Clearly this is a short circuit, but could it of caused the insulation damage or did the damage insulation cause the short circuit?

The wires remained in tact and I'm broke so I wrapped them in electrical tape thats rated for 600 volts. Will that be ok or is this a lost cause.

EDIT: Sorry here is some pics, phones not very good, but it should give you an idea.

UPDATE: I did get it working by just re-insulating the wires though my wife will have to go without the tv on all night for a while, I think its a good idea to watch it for a while. Still if any of you have an idea of what would cause this please tell me. There isn't any other damage in the unit and the fuse never blew.

 

[KrisBlueNZ]

Um... can you post some photos?

Use the Go Advanced button and click the paper clip icon.

Maximum JPEG file size is about 150k I think, so you may need to rescale the pics first.

 

[(*steve*)]

A photo would be good.

Whilst insulation tape is better than bare wires, it's not an ideal solution.

Are these mains wires? If so, you should have blown a fuse or breaker almost as soon as the short happened. In that case the insulation was probably damaged beforehand.

edit: AH! they look like they might be the high voltage wires going to the CCFL backlight of the screen. They are *really* high voltage.

 

[Alklazaris]

A photo would be good.

Whilst insulation tape is better than bare wires, it's not an ideal solution.

Are these mains wires? If so, you should have blown a fuse or breaker almost as soon as the short happened. In that case the insulation was probably damaged beforehand.

edit: AH! they look like they might be the high voltage wires going to the CCFL backlight of the screen. They are *really* high voltage.

But the gauge is so thin. I'd say as thick as your basic cheap pair of ear buds. How could it possible contain such power? Wouldn't the resistance be extreme?

I did a bit of digging and found an image of the part that the wires connect to. They start on a center circuit board. The board has HOT and COLD written on it and has a massive capacitor of about the size of a large walnut. It also houses the fuse which doesn't look easily replaceable as its sottered in. The two sets of wires leave the board and go to what I think is a video card. Then return back to the center circuit board.

The picture is not from my tv, but its does show a very striking similarity to the component I'm trying to describe. Its even located in the exact same place as my own.

 

[(*steve*)]

Hmmm, thinner than I thought, but high voltage does not imply high power. In fact, at higher voltage thinner wires can be used to carry far more power then at lower voltages.

A board that says "HOT" on it is possibly connected to the mains and you should keep your fingers well away from it when the power is plugged in (even if it is turned off) and for some time after it has been disconnected.

If those wires are in pairs (often pale pink and white or pale blue and white) and they lead off to the edge of the screen and plug in with small flat plastic plugs, then they're likely to be power to the CCFL tubes.

Better photos showing us where the wires come from, and where they go, including enough surrounding that we might recognise something would be great. Perhaps a wide shot and then some close-ups would be a good idea.

 

[Alklazaris]

Hmmm, thinner than I thought, but high voltage does not imply high power. In fact, at higher voltage thinner wires can be used to carry far more power then at lower voltages.

A board that says "HOT" on it is possibly connected to the mains and you should keep your fingers well away from it when the power is plugged in (even if it is turned off) and for some time after it has been disconnected.

If those wires are in pairs (often pale pink and white or pale blue and white) and they lead off to the edge of the screen and plug in with small flat plastic plugs, then they're likely to be power to the CCFL tubes.

Better photos showing us where the wires come from, and where they go, including enough surrounding that we might recognise something would be great. Perhaps a wide shot and then some close-ups would be a good idea.

Yeah I wish I had thought of that when I was taking pictures... its all put together now. But your completely right, thats exactly what it is 2 sets of wires, one pink, one white. They lead to the far left side where they plug into something that looks like a giant ram stick and that in turn plugs into an equally large port.

CCFL tubes? I assume thats just a name or do these advanced pixel super tvs still use tubes from the old crts?

Anyway that would be it, I'd rather not pull apart the tv its a large hassle and there isn't any other damage to the product.

 

[davenn]

CCFL = cold cathode fluorescent lamp
these are used for backlighting LCD panels in TV's and other computer monitors etc
more recently they are getting replaced with LED strip lighting

this gets rid of the 1000V or so that the CCFL requires to operate

But the gauge is so thin. I'd say as thick as your basic cheap pair of ear buds. How could it possible contain such power? Wouldn't the resistance be extreme?

as steve said hi voltrage DOESNT infer hi power the current is verry small and therefore so is the power (in Watts)

why would the resistance be extreme ? The resistance of a wire doesnt change because the voltage happens to be high. The total resistance of those connecting wires is likely to be less than a couple of Ohms

cheers
Dave

 

[Alklazaris]

CCFL = cold cathode fluorescent lamp
these are used for backlighting LCD panels in TV's and other computer monitors etc
more recently they are getting replaced with LED strip lighting

this gets rid of the 1000V or so that the CCFL requires to operate



as steve said hi voltrage DOESNT infer hi power the current is verry small and therefore so is the power (in Watts)

why would the resistance be extreme ? The resistance of a wire doesnt change because the voltage happens to be high. The total resistance of those connecting wires is likely to be less than a couple of Ohms

cheers
Dave

So there really is no way to tell what cause this short circuit? Shame I'd like to prevent it from doing it again. The only other thing I've considered is a moth might of slipped in and crossed something as we had an infestation at the time, but I saw no remains and those exoskeletons are pretty hardy.

-shrug- well its working regardless, I am quite happy just knowing I saved quite a bit of in shop repair costs for such a cheap fix.

Thanks everyone for helping me out if anything I know a lot more about LCDs now..