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Troubleshooting Annoying Problems

April 11, 2021 Comments off

You would think that when purchasing pre-made, or manufactured, cable they are built properly. Millions of XLR mic cables are made and you would think the process would be flawless. When it comes to troubleshooting annoying issues, trust your skills and your instinct. You may be surprised what you find.

My annoying problem was a noise complaint within our road system for play-by-play. This system was built 5 years ago, but only this Spring did it become a problem, but only locally in the booth. The talent and producer complained about a noise that came and went, got louder, then soft, and did not seem to go away when equipment was connected, moved, or changed out. Granted, there was always a low level background noise, but never one that created any nuisance. After Spring Training was done, I had the gear dropped off for further evaluation and troubleshooting.

My first approach to troubleshooting is to recreate the issue if I was not there to witness first hand what was going on. Maybe how I set something up a bit differently than the end user, and we all know when something goes out in the field, the users do not always do what they were instructed, and once out the door, controlled environment can and will change, causing the field person to make changes. In this case, I setup just as I would if I was “out there”. As I had a few discussion with the producer already, I was initially looking, and listening, for a ground loop type noise and issue. In addition I was looking for a bad ground connection in general as this noise grew louder at times. It also changed at different venues. I hear noise. I also knew it was in the monitoring side of life as this noise never made it to air.

After a few minutes of wiggling and checking if all connections were good, the background noise we grew accustomed to was there, but louder, so I understood their complaint. As I checked all cabling for the monitoring or local, return, and talkback audio, I was not able to isolate it. At this stage it was time to methodically check each and every connection for each talent. Starting with channel 1 on the mixer I stepped through and compared listening for any nuance between positions. I also expanded my search to outside the monitoring. I soon discovered that if I unplugged a mic cable the noise went away. Interesting to say the least as I mentioned this noise never made it to air. I moved the cable to another input, and discovered the noise continued. As I also know the equipment gets jostled around a bit while traveling I decided to check for any loose mixer components. My method: Treat it like it is used in the wild. So, I gave it a solid, but not destructive pound with my fist. With said mic cable plugged in, the noise got loud, then dropped again. I repeated without the mic cable in. Silent. Mixer good.

I have not isolated the issue to a mic cable. Remember, this noise was only in the talent and producer headphones and not on air, yet the mic cable was definitely an issue. I swapped with a known good cable, and no noise. Always use a known good at the point of localizing the potential culprit. In some cases use more than one known good to test and be sure. Out comes the cable tester to verify my findings.

Here you see an “X” pattern on the tester. Bad Boy This is definitely not normal, and this is a pre-made, or manufactured cable. This mic cable was made this way. Look closely at the pattern and notice that this cable was made unbalanced. This was not a “failed” cable as I stretched and twisted and kinked the cable throughout the length to induce an intermittent. It never wavered.

Now this is the cable test of the known good cable which I eventually used as a replacement. Good Boy As you can see here, there is a nice one-to-one pin match between the two ends.

After the mic cable was replaced, I tested the whole system again. This, my friends, is a very important step. Though at this time I found the issue, I want to make sure there are no others. In this case all was good, so I put everything back together. Once secured, I did one last check.

Why the noise from this cable? A good question. As the picture showed, this cable was made unbalanced, and since the low, pin 3 side, was connected to ground, pin 1, all would work just with reduced level. For a mic input on a mixer that is electronically balanced, with a transformer, the common mode rejection was thrown out the door. In addition, the cable itself was now susceptible to noise and could act as an antenna, allowing this noise into the system. As headphones are wired unbalanced this noise can carry through to the headphones. Since the output of the mixer is balanced and wired to the balanced input of the codec, the noise is rejected as it appears on both the high and low signal leads which are out of phase feeds, and no noise on the air.

All this was quickly fixed by just using common troubleshooting practices. Throw a little instinct in there, like the rap with the fist, and we move on to repair or replace. This setup is currently in use this weekend and no annoying noise. Talent and producer are happy. Hope this information helps, and don’t rule out pre-made cables, they could bite you later.

Cheers!

Categories: Equipment Tags: ,

Nautel NVLT and Burk Technology Config

December 13, 2013 Comments off

One thing I do like to do is help fellow engineers get to a solution to a problem.  It does not matter how small or large.  Even if I can help in the smallest way it feels good.  I’m also feel honored that engineers, companies, and tech support folks actually recommend me to others for help.  In this case, I was able to at least steer a fellow engineer in the right direction.  What we learned, and it may sound surprising, is the Nautel NVLT is DIFFERENT than the NV so much so that Burk has a different PlusConnect-NV for that box.

The rub is the PlusConnect is so new that one of Burk’s own tech support was not aware of it, or made an assumption that was incorrect.  I was not aware of how different the NVLT was until this contact.  After a few email exchanges that stated the Link was there and the ARCPlus was talking with the PlusConnect, there were no readings and the configuration did not take.  I slept on it after giving some Burk pointers.  I began to feel that something was different and directed the engineer to contact Burk and ask for more details.  A couple days later I received a call from him and did I get an eye opener:  Yes, Burk has a different PlusConnect for the NVLT, yes the MIBs are different, yes the firmware is different, and yes the AutoLoad definitions are different.  Well, that explains it all.  Burk shipped the wrong PlusConnect.  Mistakes do happen, but….

I find it interesting that my engineer friend did not learn this from the first tech support person.  Whether he was too new or did not know, a simple “I do not know, let me get back to you” would have sufficed.  It took multiple calls.  There are most likely many reasons for this, so I give them the benefit of the doubt, but still a courtesy call to make sure the proper information was conveyed goes a long way.  After the calls the Burk website (here) has been updated with NVLT firmware and AutoLoad definitions.

Now back to business.

Cheers!

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