In this article, I'm going to explain the two major types of cable failure and solutions for repairing them. After that, I'll give some tips that I wish I knew when I started repairing cables with XLR, TRS and TRS connectors.
The most common cable failure is caused by the cable wearing out due to excess bending. Most audio cables that are used in sound reinforcement have two copper cores enclosed in a wire shield and a plastic casing. In this configuration the cores can't contract and expand during bending. This lack of internal movement causing pinching on one or more of the two cores causes micro cracking in the copper core strands.
Over time use of the cable the cracks in the cores will get bigger and then eventually break apart leaving the cable in a non-working condition.
Over time when a cable is used to connect instruments, corded mics and gear; with connector sockets on the top, the cable ends up getting bent more often than it was designed to. This means that the ends of the cable degrade faster than the rest of the cable.
Degraded cable segments will feel less rigid than the rest of the cable and can be bent further without any excess force. To repair a cable in which the ends that have degraded I recommend unsoldering the connectors, then cutting off around 30cm of the bad cable then re-soldering the connectors on the ends. I also like to add shrink tub just after the connector cap to strengthen that part of the cable.
The secondary cause of cable failure is multiple breaks along the internal of the cable.
This sort of damage happens over the lifetime of the cable and is inevitable. Audio cables are not designed to last forever and eventually they will have degraded or failed segments along the entire length of the cable.
You can't do much to repair the cable at this point because there are so many problem sections that if you cut out all the bad parts you would not have any or much cable left. On the upside, connectors tend to outlast the life time of the cable and can be reused. However while the metal parts on connectors will normally still be good the plastic caps and cable restraints can become brittle over time but not every connector has plastic parts. As connectors can be rather expensive to buy new it's a good idea to keep the connectors as is a cheap way of getting connectors.
So what to do with the spare connectors? Well you can do two things with them:
A) Use the connectors to make new cables as connectors can be expensive to buy by themselves. Stores like Jaycar and Tandy sell audio cable without connectors at about $1.50-2.00per metre which means you can make cables as long or as short as you like. However keep in mind that the length and quality of the replacement cable will affect the integrity of the audio signal and the lifespan of the cable.
B) Create adaptor cables. Adaptor cables can be useful for connecting equipment with TRS/TS sockets to equipment with XLR sockets and vice versa. Although there is some equipment that won't be compatible due to balanced and unbalanced connection standards and differences in the amplitude audio. Another reason to build your own adaptor cables is that cable manufacturers may not have a model of adaptor cable you need. Building your own may be the only way of obtaining the right adaptor cable for the job.
Over the last few years I've learnt a lot about soldering and there are a lot of things I wish I knew when I started that I learned the hard way:
â€¢ Always tin every cups/pads and wire as it will make stronger solder joints.
â€¢ When buying XLR connectors make sure the walls of the cups are as thin as possible as it will make heating up the solder easier.
â€¢ Cheap TRS/TS connectors are harder to work on than the more expensive ones.
â€¢ Use as little flux as possible and make sure you remove any flux residue. It's good to get a clean surfaces by using flux but too much will make the solder joints harder to melt in 2-5 years' time; when you working on the connectors again. I've worked on some 10 year old XLR connectors with flux all over the place and they had thick walled cups and it was impossible to melt the solder as I could not get the iron hot enough.
â€¢ Get a high quality solder that has a flux core. Oxidisation can cause bad solder joints if you don't use some flux or solder with a flux core. The cheap solder also tends to not flow as nicely and is harder to work with.
â€¢ Solder has lead in it and you can get lead free solder but the lead free solder has a higher melting point and is a lot harder to work with.
â€¢ Always solder in a well-ventilated area as you can get lead poisoning and make sure to wash your hands after soldering. No one wants to eat a lead ham and tomato sandwich at lunch!
â€¢ Get a good quality soldering iron. The battery ones won't last long enough to do more than a couple of joints before needing new batteries and the cheap wall powered irons tend to overheat the solder making it unusable.
â€¢ When placing the wire on TRS/TS connectors don't put it through the tabs eye and twist the wire back on its self. Doing this will make unsoldering the wire impossible.
â€¢ Apply enough heat to make a good solder joint as continuing to overheat parts of the connectors can warp parts of the connectors to a point where they won't fit into other connectors or sockets.
â€¢ Using a vice or helping hands to hold what you're soldering still is a big help and keeps your hands free. Be careful not to over tighten the vice as this will crush the connectors.
Zach Radloff lives on the Gold Coast and is studying IT and Multimedia at university and is also a qualified Live Production, Theatre and Events Operation Technician.
Zach Radloff's previous articles may be viewed at www.pressserviceinternational.org/zach-radloff.html