Don't Forget to Check the Cable

We’ve been talking about the transition to IP-based networked AVL systems for quite some time. I just finished up a big install for a church in which every system is IP-based. Audio is Dante, lighting is Streaming ACN and while video was SDI, the router and switcher lived on the network and were remotely controllable. All these systems are extremely flexible, powerful and offer the church great capabilities. They also come with some setup and configuration challenges. I spent as at least 2-3 times the as long getting everything playing nicely as I did actually tuning the PA and building show files.

These system can also be challenging to troubleshoot. And with everything now in IT switches, it’s easy to assume that any problem you have is IP related. However, sometimes, it’s something far more simple—and frustrating. Here are few examples of things I ran into that turned out to be a lot simpler than we originally thought. 

Is It Getting Power?

We installed an RGBW house light that was driven by DMX. The fixtures have their own control box that sends out a proprietary control signal that we initially had some challenges with. Once we worked that out, it all seemed to be working, until we lost half the lights in the youth room. The lights were split into two circuits and two runs of control. Those runs coincided. I spent a few hours trying to troubleshoot the control signal, wondering why it wouldn’t turn on. 

Finally, I grabbed by non-contact voltage tester and found out they weren’t getting AC. I went back to the relay rack and found a fuse blown on the relay tray. Curious as to how the fuse was blown, I shut power off to the relay panel and tested all the hot busses for shorts. Sure enough, we had a short in a different circuit. The electrician accidentally landed a neutral on a hot lug and when we put the relay tray in, it blew the fuse. We didn’t know that, as we hadn’t used that circuit yet. And when we pulled the trays out to connect DMX, we mixed up the order and ended up with the blown fuse in the house light slot. Before you go spending a ton of time trying to sort out IP/IT/DMX/SCAN issues, make sure the fixtures are actually getting power. Lesson learned. 

Is the Pinout Right?

In this same system (it was a frustrating day), we came out of a SCAN gateway to DMX to drive the control box. The gateway used a terminal strip, and the control box used a 5-pin connector. So, we cut the end off a 5-pin cable and landed the wires. My installer had done the exact same thing in another room in this install, so it seemed logical to land the wires the same way.

Three hours of troubleshooting streaming ACN, DMX, gateways and all that nonsense and one of my guys suggested opening up the 5-pin to verify the pinouts. Sure enough, the manufacturer of this 5-pin cable (who will go unnamed, but will not see a ton more business from me) decided that sticking to a single color scheme for all DMX cables is simply too much work. In one cable, shield, data + and data - were bare wire, black and red, respectively. In the other room where I had so much trouble, it was bare wire, red and green. Once I swapped wires, all worked fine. 

Lesson learned; never trust a cable manufacturer to do a good job managing colors in 5-pin (or even 3-pin for that matter) cables. 

In each of these cases, a simple analog cable caused me a ton of headaches. I should have checked them first, but I was sure it was a network issue. When troubleshooting newer systems, don’t forget the basics. Is it hooked up properly? Is it getting power? Is the In cable going to the In port? Often, we spend a lot of time trying to solve a problem that doesn’t exist.

Roland