Hey - It's another Clearcom thread!

[RideTheSquirrel]

So, I've spent the last hour searching through an abundance of clearcom thread's in this forum. There are definitely plenty of them to be found, but I have a new one for you guys.

Background:
This coming Wednesday I'm going to be diving into a clearcom issue that I've never really come across before. I'm not certain of the model of the rack unit we have right now, but I will update that info on Monday with some pictures as well. I know it's a 2-channel wired unit that is installed into a 800 seat theatre located at a University. We have 10(ish) RS-601 belt pack units that all have their own wired connections at various points throughout the theatre. We also have 6 box units that are installed into the wall in dressing rooms, etc. We probably do 25-30 shows a year during the academic year.

Problem:
On Channel B we randomly get this pulsing that happens. It's like consistent Morse code "dot dot dot dot dot dot dot..." it goes on forever. This happens across BOTH Channel A and B when it occurs. If you unplug the XLR connection into Channel B at the Rack Unit (which is located way up in a Projection Booth up on the balcony level FOH) the pulsing stops. Sometimes it's very fast (think faster than 200 beats per minute), sometimes it's relatively slower in comparison (like 150 beats per minute). If you leave it unplugged long enough (most likely for all the signal down the line to deplete) it will go back to being fine for maybe another 3 or 4 months. This is the wildest gremlin ever because of how infrequent it is. I will admit - the clearcom unit is left powered on constantly 24/7 365. When this issue isn't occurring the coms are working perfectly. No hum, no buzz.

Anybody else ever experience this, or have a solution?

Trust me - I know there are bigger fish to usually fry, however with this not working 100% it has nearly burned us a few shows.

 

[AudioGreg]

probably cell phone data transmissions. look for a cell phone lying on or near a speaker station. they seem to pick up this noise pretty easily…

 

[RideTheSquirrel]

I thought perhaps it was that too, Greg. It doesn't go away though - I know the data transmission interruption your speaking of because my audio speakers for my computer at home pick them up all the time if a cell phone is too close. This is more like a power feedback loop. The pulsing would never ever stop if we didn't unplug the B Channel and wait for the power to the line to die. Even then sometimes if we don't wait long enough before plugging it back in it will resume sometimes at faster or slower rates. Hopefully that helps narrow down the possibility.

 

[RideTheSquirrel]

Ok - so I figured out what the problem was...

The Clearcom unit was at the top of this rack; What Nightmare, right?! I should also add that this doesn't look half as bad as it did. At this point I had removed ALL the power cables from the equation to try to make sense of this cluster!

Every ounce of my being cringed when I opened the rack to see this. So I fished around a bit to isolate wires and clean things up and I found this to be the problem. A horribly grounded set of wires, and another set of wires going nowhere that were seemingly acting like an antenna!

So after I did some re-wiring and tested. Everything was absolutely perfect with the coms. Crisp, clean, and perfect signals all throughout the house! It's my philosophy to always leave something better than when you found it, so here's the end product.

 

[Jay Ashworth]

Love that label on the stick-on; what's it do besides killing newbie engineers?

 

[RideTheSquirrel]

The little black box is a low level pre-amp. We have a pair of hanging mics in the house that also play on the B channel constantly (which goes to the dressing rooms, etc) so performers can hear where we're at during the show.