Cable Tester

Because cabling is so vital to powering lighting gear, as well as for making control signal connections, you should have some kind of cable tester in your tool kit that is appropriate for the kind of cabling you use. Of course, you can always use your DVM/VOM for testing continuity between the two ends of a cable, but it's not as convenient to use for multi-part cables such as cat5 cable, which has four pairs -- 8 wires inside the protective sheath.

(graphic - cat5 pinout here with colors) (photo here of actual cable)

One simple tool is a network cable tester for cat5 type cable. It also works fine with cat5e, cat6 and cat6e cable as those are just higher grade versions of the common, 8-wire cat5 cable. A network cable tester doesn't have to be expensive -- this one can be found for less than $10.

(photo of tester)

Simply plug the cables into the ends and flip the power switch -- the diagnostic LEDs light in on both tester sides simultaneously as each cable is tested. This tester makes it easy to see when a cable is reversed or out of order. If one of the LEDs doesn't light at all, it means that either one (or both) of the plugs is not making good contact on the wire on that pin number, or possibly that there's a break in the wire somewhere in the length of the cable.

When an LED comes on out of order, a close examination of the colors of the wires in each plug should tell you which plug is correct and which is wrong: cut off the bad plug and attach a new one.

When an LED doesn't com on at all, try recrimping both ends of the cable and retest. Sometimes that fixes the problem. If not, try a close examination of both plugs to see if you can discern which one might be bad. If you can't tell, well, you have a 50-50 chance on selecting the bad plug: cut one off, replace it and test the cable again. If you end up replacing both plugs and still the same line doesn't come on, the cable likely has an internal break somewhere. Those are much harder to find, and it's usually much faster just to replace the cable.

NOTE: Before you toss the bad cable out, remember that controllers, SSRs and communication gear don't always use all 8 wires in a cat5 cable. If the "dead" line is one that's unnecessary anyway, the cable can still be useful! So it pays to know how your equipment interconnects -- it can save money!

Common connections for cat5 cables

• Controller to remote SSR

Pin 1 - orange/white - +5v power

Pin 2 - solid orange - channel A signal (of a 4-channel SSR)

Pin 3 - green/white - no connection

Pin 4 - solid blue - channel B signal

Pin 5 - blue/white - no connection

Pin 6 - solid green - channel C signal

Pin 7 - brown/white - ground return to controller (optional, not all controllers support this)

Pin 8 - solid brown - channel D signal