[spencexxx]

Hi, I'd never picked up a soldering iron before and have noobie understanding of electricity and soldering. I bought a 30w iron and decided to try to solder a piece of Coax cable (cheap Cable TV Cable) for practice. I have some Cardas Coax for when I get good enough to make a cable.

Here's what happened: I cut a 10 inch length and while stripping off the white outer wire, realized that I could pull off the entire white plastic coating. This left the braided silver colored wire over a plastic tube containing the solid-core wire. I stripped down to that. I tinned the iron then tried to tin the copper(?) solid wire (it dripped off)....then I unwould the silver wires from the outside creating a Y .... I touched the iron to the twisted 1" of silver wires and attempted to tin them and F L A S H ! A pop and a white light that blinded me for about 5 minutes. When I could see again (without the yellow/blue tone) I see that the silver braid is burned and exploded in a patch about an inch long and about 4 inches from the twisted end. It looks like I held a lighter under it.

I would like to build a coax rca at some point, but do not want to obliviate the expensive Cardas...nor do I want to scare the hell out of myself again. I'm sure someone will read this and say "Oh, of course, you idiot! You ___________" Please help me to fill in the blanks!

 

[pdupiano]

do you have pictures? or it might be your avatar... its the curse of head-fi

 

[spencexxx]

No curse on that!

Pics are here:

http://farm3.static.flickr.com/2653/...096f25fb_b.jpg

http://farm3.static.flickr.com/2615/...9f441f43_b.jpg

 

[wuwhere]

The braided wire has two uses, an RF shield and ground. Underneath that, there is another RF shield, the very thin aluminum foil.

 

[wuwhere]

After thinking about it, your soldering iron is so hot that it burned and vaporized the braided wire.

 

[Billyk]

That's pretty odd alright, don't think it's a normal occurrence.
What kind of iron are you using?

 

[spencexxx]

Silly question, but it's a 30 watt $5 job.... I left it plugged in for 10 min ... does it just keep getting hotter until it creates nuclear fission?...how can I avoid that in the future?

 

[Billyk]

Do you have a meter? I am curious as to whether the tip is live for some reason and it grounded creating a short when you touched the wire. Being to hot doesn't make sense to make as big a reaction as you described, it sounds like a short to something as powerful as mains voltage. Just a guess.

 

[wuwhere]

I doubt that its a short. Unless the braided wire is attached to something that would sink the current.

 

[3amsleep]

I remeber a season of the simpsons were almost everything exploded...

... if its a cheapo iron there's a possibility that you made a short circuit somehow, thus forming an electrical arc. Or maybe there were powdered alumminum leftovers from fabrication in the cable that vaporized..... But I would go with the electrical arc, since the vaporization point of alumminum is around 2500 °C (4500 °F), so even if it's a low level alloy its very unprobable.

Anyways what happened to you isn't common at all, so you might make it a war story as well.

 

[spencexxx]

I bet I know what could have contributed to this! The comment about conduction...I didn't want to slop solder on the table...so I was using the stove plate as a workspace...that might have been a dumb idea. I wonder if I shorted out my iron...
I didn't know a soldering iron had much to do with electricity (aside from heating up) Are you supposed to unplug it before you use it and then plug it back in to heat it back up?

All this is turning into a huge confusion for me as I watch youtube videos of 7 year old girls explaining how easy it is to solder while I'm shooting lightning bolts across my kitchen!

EDIT: @ BillyK : No, I don't have a meter. My tool collection consists of a pair of pliers and a wrench set that I sometimes use to drive small nails. I unplugged the iron right after that, but I did notice that it was "singed" up to the screw you would use to change out the bit. I'll plug it in tomorrow and see if it still heats up. Its 3am though, so I'm going to sleep...I'll check back here in the morning!

 

[3amsleep]

Quote:

Originally Posted by spencexxx /img/forum/go_quote.gif I bet I know what could have contributed to this! The comment about conduction...I didn't want to slop solder on the table...so I was using the stove plate as a workspace...that might have been a dumb idea. I wonder if I shorted out my iron... I didn't know a soldering iron had much to do with electricity (aside from heating up) Are you supposed to unplug it before you use it and then plug it back in to heat it back up? All this is turning into a huge confusion for me as I watch youtube videos of 7 year old girls explaining how easy it is to solder while I'm shooting lightning bolts across my kitchen! EDIT: @ BillyK : No, I don't have a meter. My tool collection consists of a pair of pliers and a wrench set that I sometimes use to drive small nails. I unplugged the iron right after that, but I did notice that it was "singed" up to the screw you would use to change out the bit. I'll plug it in tomorrow and see if it still heats up. Its 3am though, so I'm going to sleep...I'll check back here in the morning!

yeah, then it was a shortcircuit between the cable and the iron. if I were you I would ditch that one and buy a decent one... do it, for your own sake.

PS: you might want to frame the magical iron.

 

[wuwhere]

Well, soldering iron heats up by passing current through them. The braided wire becomes a conductor of current. If the current is too high for it to conduct, it becomes a resistor and will explode, literally, from the high current that its trying to pass but can't handle. So its not really a short.

 

[3amsleep]

Quote:

Originally Posted by wuwhere /img/forum/go_quote.gif Well, soldering iron heats up by passing current through them. The braided wire becomes a conductor of current. If the current is too high for it to conduct, it becomes a resistor and will explode, literally, from the high current that its trying to pass but can't handle. So its not really a short.

I dunno, alumminum is more a conductor than a resistive metal (28.2 nΩ·m), I think an electrical arc is more possible. Also I've actually read about coaxial wires acting as high voltage capacitors, so thats a possibity too. but vaporizing alumminum is really hard, and to do it using electricity you would need a high voltage arc in the first place, that would turn the aluminnum into plasma, much like a railgun.

 

[Billyk]

Well, I would not use that iron again. Perhaps framing it would be a good idea, the "thing that coulda kilt me" would make a good title for it

Don't give up whatever you do. This is a fascinating hobby, I am sure you will like it. A decent meter is a good investment, but perhaps a $10.00 iron would be the first thing to get!