How to find a break in long multi-wire cable? Roland GR

[Rodgre]

I have a 24-pin cable for my Roland GR-300/G-505 and I noticed the system acting buggy lately then suddenly lost communication between the guitar and synth.

I've tested for continuity on each conductor from end to end and two wires are not making contact.

Does anyone know of a way to test along the length of a cable to try to estimate where the break would be? Maybe some means of running a signal through the wire and testing it with some sort of meter along the insulation of the cable to see where the signal stops? Something along the lines of those testers that can sniff out where your AC lines are within your walls?

Short of that, anyone know where I can get some 24-conductor Mogami cable to make a new cable from scratch? Didn't think so....

Roger

[Mark Hammer]

Our pet rabbit chewed through my GK-1 cable, and I had to simply cut it in half.  Now I have to splice all those free ends together.  You have my sympathies.

[Nasse]

Take first your eyeball in your hand and look very close )buy cheep, reading glasses if yo are old and magnifying glasses too and good light(

2) then do some thinkin

I have had a little success with the needle technique, I have put thin needles trough insulation and then take ya some emeasurements what ya can

4) You can look if some sharp cornered heavy one has been  on there too

3) Dunno but i think it is best to power off before doing anything

[Rodgre]

The cable itself looks fine. No crimps. No odd bumps. I've tugged on the wires at both ends and they don't seem to be broken near the ends.

I could cut it in half but it's only 16' long and that's not very long to begin with.

I'm tempted to be really low-budget and run two wires on the outside of the jacket and connect the broken wires that way, heat shrinking over the whole cable, but that's not exactly my favorite idea.

Roger

[frank_p]

If you have a cap. meter (or someone near your place have one): You could try to check for capacitance between one end of the broken wire and an OK one, then do the same at the other end of the cable.  The side with less capacitance should be the side where it is broken.  Since you have a lot of wires it may not be that obvious, but why not try it.

[waltk]

If you don't mind spending hundreds or thousands, you could get a TDR (time-domain reflectometer).  Or better yet, if you have access to a friendly network technician at a large company, you ask could him to test your cable with one.  A TDR will report the actual distance to the break.

Or, on a budget, a network wiring tracer (under $100 from home depot) might work.  It comes in two pieces - one injects a signal on the wire, and the other let's you detect it.  You would just run the detector along the cable until you find the break.

[Rodgre]

I'm thinking that I am going to go with replacing the cable with a Belkin printer cable and just start from scratch. Seems a lot cheaper than trying to detect where the break is in this 30 year old cable.

Thanks for the help.
Roger

[iaresee]

This reminds me of a story one of my profs liked to tell in Engineering school. Old guy, he'd been around...a while...but loved to teach so there he was. He found his EE calling when he was in the army (I want to say Polish, but I know the German's captured them...maybe not all the Polish army was conscripted? It was definitely some Eastern European army...) in WWII and one of his jobs as a young whippersnapper cadet was to cut the power lines to German towns they were about to attack so, you know, the German's wouldn't have any power. And he was fascinated by the fact that every time they cut a line the German's new, with pretty good accuracy, where they were and shot at them.

When he got out he went to Engineering school and then on from there...

Great guy. Had a ton of stories like that.

[Processaurus]

You have a couple NC wires in the 24 pin cable system you can hi-jack to reconnect to your broken wire (you can leave the broken wires connected), and if those break you can still steal one of the ground wires, as roland used a few for lower resistance... 
http://www.joness.com/gr300/24pin.htm

I got a good deal on one of the weird aluminum Ibanez 24 pin cables because it had a break in the G string conductor, now it's properly kludged back together by stealing the Pin 7 wire.

[Mark Hammer]

I'm hoping to score one of those older casio MIDI-equipped guitars in a few weeks, so that I won't have to deal with the big cable ever again, and just use easily replaceable MIDI cables.

[noelgrassy]

These goomers have bulk Canare & might have the Mogami to lash a cable together. Then you'll probably need some
proprietary crimping device that cancels everything.

[aron]

The needle is not a bad idea to me.

[Vitrolin]

what if you replace the two broken wires with new ones but on the out side, if it has shielding, they should be shielded of course,

[Processaurus]

But surely he doesn't need do do anything except relocate the unused (pin 7) wire inside the cable to the pins used by the broken wire?  It's a 5 minute repair.