DIY Mystery
May 6, 2009 at 8:20 AM Thread Starter Post #1 of 43

scootermafia

MOT: Double Helix Cables
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So, I built myself a new RCA cable. A pretty easy task. I put it all together, check continuity, then put on the hot glue.

I plug it in and it sounds messed up. I check continuity and sure enough there is a little bit of resistance between signal and return in the RCA cable. What the hell.

I guess which RCA plug is the problem, and desolder the wires there. The glue is heated enough to slide the wires out. I test the RCA plug with the cable attached, no short. I test the RCA plug with some glue in it, it has a short, laughing at me like a severed head that's still alive.

I heat the glue up and start scraping it out. There's still a short. After I scrape a little more, all of a sudden, no short anymore. This is a Cardas SRCA plug. I'm also not a moron. Where the signal and return wires attach is nowhere near each other, it is by no means an even remotely delicate task to do compared to other plugs, and there's no way I could have gotten solder anywhere that could have bridged the center pin to the plug body - there's a substantial area of teflon in the center as insulation and the gap between center pin and the ground metal is aplenty. With such a huge gap you'd need a fair bit of obvious metal substance to connect the pin to the ground. I flow all the glue out with 600 degrees heat until it's nice and clean inside, and scrutinize the inside. There's no evidence of any little bits of metal trapped in the glue I scraped out. There's no evidence that any solder was even on the outside of the center pin that could have caused the short. The teflon dielectric protecting the center pin is squeaky clean. Solder crusted onto metal, overflow, does not come off easily at all and my delicate scraping out of most of the glue could not have possibly knocked something loose, but something was connecting the center pin to the return. Anyone else had a cable short mystery?

Long story short, I wasted 2 hours figuring all this out. What the hell.
 
May 6, 2009 at 9:03 AM Post #3 of 43
Quote:

Originally Posted by scootermafia /img/forum/go_quote.gif
So, I built myself a new RCA cable. A pretty easy task. I put it all together, check continuity, then put on the hot glue.

I plug it in and it sounds messed up. I check continuity and sure enough there is a little bit of resistance between signal and return in the RCA cable. What the hell.

I guess which RCA plug is the problem, and desolder the wires there. The glue is heated enough to slide the wires out. I test the RCA plug with the cable attached, no short. I test the RCA plug with some glue in it, it has a short, laughing at me like a severed head that's still alive.

I heat the glue up and start scraping it out. There's still a short. After I scrape a little more, all of a sudden, no short anymore. This is a Cardas SRCA plug. I'm also not a moron. Where the signal and return wires attach is nowhere near each other, it is by no means an even remotely delicate task to do compared to other plugs, and there's no way I could have gotten solder anywhere that could have bridged the center pin to the plug body - there's a substantial area of teflon in the center as insulation and the gap between center pin and the ground metal is aplenty. With such a huge gap you'd need a fair bit of obvious metal substance to connect the pin to the ground. I flow all the glue out with 600 degrees heat until it's nice and clean inside, and scrutinize the inside. There's no evidence of any little bits of metal trapped in the glue I scraped out. There's no evidence that any solder was even on the outside of the center pin that could have caused the short. The teflon dielectric protecting the center pin is squeaky clean. Solder crusted onto metal, overflow, does not come off easily at all and my delicate scraping out of most of the glue could not have possibly knocked something loose, but something was connecting the center pin to the return. Anyone else had a cable short mystery?

Long story short, I wasted 2 hours figuring all this out. What the hell.



sorry, no idea.

re: Naim pin-out cable queries. are you planning on powering a Naim NAHA2 HP amp via your sigama-11? i used to own the Naim and rated the HP amp. i also owna an M3/sigma-11 and have contemplated DIYing a clone of the NAHA2.
 
May 6, 2009 at 9:50 AM Post #4 of 43
Hi there, I have a close friend that bought a Headline and I'm better at DIY than him so together we figured out how to make a Naim adapter, and put one together. Got it figured out. I hear good things about the Headline, it's probably a nice amp, I'm curious what it has for circuitry.

M3 + Sigma work for me though, they're great.

No, my hot glue is not conductive. I had a fantasy in my head that somehow the glue and solder combined but I don't think that's likely at all. It's ordinary hot glue and I use it all the time for everything. I really can't see how or where there would have been a solder bridge. The only place it could have been hiding is on the teflon dielectric and I would have seen it.
 
May 6, 2009 at 10:30 AM Post #5 of 43
Quote:

Originally Posted by scootermafia /img/forum/go_quote.gif
No, my hot glue is not conductive.


Did you try it with a multimeter? I've seen this happen to several people on this forum. I haven't used hot glue in this way myself, but I would test mine before using it on a connector.
 
May 6, 2009 at 10:43 AM Post #6 of 43
I have had a sharp solder cut off poking through the heat shrink and touching the outer barrel. I stole an emery board from my wife so I can file them down. She hates it that I sometime re-purpose her female gear to do male things.
 
May 6, 2009 at 11:07 AM Post #8 of 43
Quote:

Originally Posted by rembrant /img/forum/go_quote.gif
She hates it that I sometime re-purpose her female gear to do male things.


Its worse when they take our stuff and do female things
smily_headphones1.gif
That is a crime indeed.
 
May 6, 2009 at 1:10 PM Post #9 of 43
not know the type of plug used, is it possible that when you assembled the plug that a short occurred then? I had this happen with a 3.5mm plug because when I assembled it the twisting to screw the outer piece on cause the lug inside to twist and then short.
 
May 6, 2009 at 2:29 PM Post #11 of 43
I had the same problem with an LOD and I resoldered everything nothing worked. Wound up changing the plug and it worked perfectly. Still curious why it happened but my guess would be some dialectric stuff getting caught between the wire and the pins of the connector. In this case it might be glue/excess teflon from wires/too much heat melting the plastic separating the metal pins.
 
May 6, 2009 at 2:43 PM Post #12 of 43
Hot glue is basically plastic (usually a polyethylene compound) so I'm pretty sure that wasn't the cause.
I've had a tiny strand of wire bridge the center pin and the shell. It probably broke when I twisted the shield together, fell into the shell and I didn't see it. I've heard of a hair (it's conductive) causing a bridge.
It sounds like a fluke occurence and when you pulled out the hot glue you pulled out the bridge, even if you can't see it.
 
May 6, 2009 at 2:56 PM Post #13 of 43
plastic conducts, it just doesn't conduct as well as other materials. Pretty much anything can conduct electricity, including electrical tape. The issue is if somehow there is a dialectric (like certain plastics) that get stuck in between two metal components (this is how you make a capacitor). When that happens, there is an added capacitance in the chain and you get the garbled sound that scootermafia was describing. Then again I could be wrong, but I see no other way of describing what's going on. I mean we can say faulty connectors all we want but they'res really VERY little that can be inherently faulty with a connector if it conducts like its meant to. The only difference would be the impedance/conductivity, which would never lead to what scootermafia describes in his post. So don't count out the glue, plus have you ever seen a small tesla coil wrapped in 3 layers of electrical tape conducting electricity... trust me anything can conduct electricity, you just have to have the right conditions.
 

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