To continue the series of “Little Hacks”, here’s LH-2: Guitar Cable Tester.
LH-2 is a very simple device I contrived at the same music shop with the same resources of LH-1: External Electric Guitar Tone Control.
The design was inspired by a cable tester we used in the store. The Signalflex SF-CT (old version) was a black metal box with the typical music / stage connectors like XLR, 1/4″, and RCA. While thumbling through the tool box probably looking for the diagonal cutters I could never find, I noticed the SF-CT and it’s crazy $40 price tag we had stamped on it.
So on one of those lonely, slow nights, I decided to disassemble this little black box. Shortly after, I determined it was essentially an expensive box of wires that were tangled all over each other, leading up to one resistor and an LED. I’d pay the $40 just to never have to open it up again and deal with that headache.
Anyways, I’m sure there was a good reason for all the wiring, and I’m not contesting that. I was simply interested in how to create my own one of these to avoid the crazy price tag.
So, after scouting out a resistor, LED, 1/4″ phono jacks, 9v and a rubber band – I produced this awesome little device.
Here’s the super simple schematic:
Function – 20ft electron detour
Essentially we take a guitar cable that is suspected to not work correctly. Next, (without having to go over to grab a guitar and find an amp that’s actually plugged in, sit down, and get situated far away from the workbench) we just plug both ends of the cable in to the jacks on the tester. Our little bit of voltage starts from the battery’s (+), goes through our complex signaling system ( resistor + LED ), then into the cable’s hot lead ( tip ). The electrons flow all the way through the line to the opposite jack. The opposite jack simply jumps the tip and sleeve ( ground ) sending the flow back through the cable ending at the ( – ) terminal of the battery.
If there is continuity, the LED will light, and then the cable is good! If not, well wiggle it around for a bit to see if that LED will flash at you.
The purpose of this was not to make an amazing discovery, but just to challenge myself to see if I could create a device out of spare parts that could actually be of use. Something this small is useful for stage technicians that have a constant cluster of bad cables – a pocket sized tool would be ideal for quick checks.
For a more practical and finished product, I would design it with a much smaller battery and build it into some type of small enclosure. The 9v provides way more voltage than necessary, and it’s way to bulky.
I might actually make a finished version of this eventually.