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Author Topic: Static Cat5e STP????  (Read 1574 times)

dave milton

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Static Cat5e STP????
« on: March 11, 2019, 04:18:33 pm »

Had a problem with pops/snaps in my mains, and sometimes a couple of little signal dropouts as well, the other day.

What's odd is that I've used the exact same rig/setup in this venue a few times before with no issues. 

I'm running an X32 console, two SD16 stage boxes, connected by a decent quality Cat5e STP cable with Ethercon terminals. 
The problem only showed up when someone walked CLOSE to the cable but not stepping on it.  It was taped to a wooden floor, but right next to a run of carpeting.  I won't go into all the things I tried to diagnose/fix the problem, but I did manage to deal with it.

What I'm not 100% sure about is my diagnosis of exactly the problem was. 

In the end I decided that what was causing it was static buildup in the carpeting (that was close to the cable but not touching it).  When someone walked along, they built up the static charge enough to cause a little shock.  While the cable IS shielded, it was enough of a charge in the field around the cable as to cause it to dork a bit, which manifested in a signal pop or loss sent to the speakers.

Does this make any sense?

thanks for your help,
d.
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Tim McCulloch

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Re: Static Cat5e STP????
« Reply #1 on: March 11, 2019, 05:14:47 pm »

I'd get out my Ohmmeter and check continuity from Ethercon shell to Ethercon shell.

Are the S16 jumped together or do you use 2 CAT runs back to the mixer?  If you use a jumper, it too must have ground continuity between Ethercon shells.
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Michael Storey

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Re: Static Cat5e STP????
« Reply #2 on: March 12, 2019, 02:19:06 am »

Had a problem with pops/snaps in my mains, and sometimes a couple of little signal dropouts as well, the other day.

What's odd is that I've used the exact same rig/setup in this venue a few times before with no issues. 

I'm running an X32 console, two SD16 stage boxes, connected by a decent quality Cat5e STP cable with Ethercon terminals. 
The problem only showed up when someone walked CLOSE to the cable but not stepping on it.  It was taped to a wooden floor, but right next to a run of carpeting.  I won't go into all the things I tried to diagnose/fix the problem, but I did manage to deal with it.

What I'm not 100% sure about is my diagnosis of exactly the problem was. 

In the end I decided that what was causing it was static buildup in the carpeting (that was close to the cable but not touching it).  When someone walked along, they built up the static charge enough to cause a little shock.  While the cable IS shielded, it was enough of a charge in the field around the cable as to cause it to dork a bit, which manifested in a signal pop or loss sent to the speakers.

Does this make any sense?

thanks for your help,
d.

I'd start by confirming continuity between your Ethercon shells, as Tim suggests.

What length of cable you're using? I used some nice cables from CBI that were pretty much the max length spec'd by Behringer at the time (300' if I recall?). Had no issues for quite some time then all of a sudden had the ballroom show from hell. I've since switched over to the Midas NCAT5E-50M (164') and things have been flawless **knocks on wood**.
« Last Edit: March 12, 2019, 02:23:17 am by Michael Storey »
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Michael Storey

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Re: Static Cat5e STP????
« Reply #3 on: March 12, 2019, 02:22:11 am »

Are the S16 jumped together or do you use 2 CAT runs back to the mixer?  If you use a jumper, it too must have ground continuity between Ethercon shells.

I suppose this applies even if the two S16 are in the same rack and grounded together via the rack rails?
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Dan Mortensen

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Re: Static Cat5e STP????
« Reply #4 on: March 12, 2019, 03:32:14 am »

I suppose this applies even if the two S16 are in the same rack and grounded together via the rack rails?

Definitely.

It's not a grounding problem as we normally think of grounding, it's a signal/cable protection issue requiring continuous grounded envelopment  from chassis to chassis for signal-carrying cables. That each chassis is separately grounded to the same or a different ground* is almost completely irrelevant to the solution to the Electro Static Discharge (ESD) problem, which may not be the exact problem we are dealing with here since there is no allegation that a charged human is touching a device on either end and causing a spark. Since there is insulation on the cable one would think that touching it would not cause a spark.

*The effect of different grounds for devices on the two ends of the cable is as yet unknown AFAIK. One presumes it's not helpful.

Having no safety ground on a chassis at one or both ends of the cable means there is no safety protection from life threatening problems and should be strenuously avoided.
« Last Edit: March 12, 2019, 04:01:40 am by Dan Mortensen »
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Dan Mortensen

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Re: Static Cat5e STP????
« Reply #5 on: March 12, 2019, 03:49:39 am »

In the end I decided that what was causing it was static buildup in the carpeting (that was close to the cable but not touching it).  When someone walked along, they built up the static charge enough to cause a little shock.  While the cable IS shielded, it was enough of a charge in the field around the cable as to cause it to dork a bit, which manifested in a signal pop or loss sent to the speakers.

I want to hope this is not what was happening because it opens up a whole host of problems that grounded shielded cable should be immune from.

After checking Ethercon connectivity and finding it good, assuming it is, I have to ask how old the cable is, how much it's been used, and what kind of shield it has? A foil shield can break up over time, I know that for sure, but what I don't know is how much turning into little pieces affects its functioning as a shield.

For RF, I think we've determined that holes in metal as big as an inch still are a barrier to radio frequencies. If DC needs a continuous shield in order to protect, or even a very tight braid, shredded foil may not do the trick anymore. But I don't know for sure.

When someone walks on carpet, isn't the charge built up in their body and not in the carpet? I don't know but have always assumed that the charge was in the object being rubbed and not the fuzzy thing doing the rubbing.

It sounds like the people walking near the snake were not actually close enough for the charge on their bodies to discharge into the snake. Is that so? That's a conceptual problem if it is, because that means something is jumping some distance rather than by contact.

Edit: While expanding on my response to Michael above, I wondered if your snake is missing chunks/has cracks in any of the jacket so the shield is exposed?

I hope you're proud that you are the first to report this exact problem AFAIK, and also hope that you keep trying to find the answer and tell us about it when you do.
« Last Edit: March 12, 2019, 04:08:18 am by Dan Mortensen »
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dave milton

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Re: Static Cat5e STP????
« Reply #6 on: March 12, 2019, 09:40:37 pm »

OK, some more details and info for everyone to see if we can figure this one out for real.

First of all, I have not had a chance to test continuity shell to shell, but will as soon as I'm able.  This will probably be the most important detail to know of course.

Second, understand that I have used this exact same rig/gear/setup in this exact venue/location a few times with no problems.  I've also used this same console/cable/stage boxes/speakers a bunch of other places with no problems.

Third, when I "fixed" this problem the other night, I moved everything, using the same cable, to another location (away from the carpet) and had no problems whatsoever for three performances and some other rehearsals.

So, now some random other facts and details:
* The cable is about a year old, has not been used heavily, has always been stored/kept on a reel, and is/should be in very good condition.  This is not something that gets a lot of use/abuse.
* The cable is 150' long.
* The mix position was about 75' from the stage boxes and speakers.
* The cable ran along a wooden floor, and was taped down along the edge of the carpet about 50' of the way.
* The ONLY place where someone walking close to it that caused the pop/snap was about midway between the mix position and stage boxes.  No one stepped on the cable.  The zone in question was about 2'-5' from the cable, and about 12'-15' lengthwise along the cable run.  No other location manifested in a problem, including anywhere close to either end.  Perhaps importantly, that zone included some steps on carpet and also some steps on wood.  It was far enough from any of the gear plugged into either end of the cable as to not cause them to move/shake/shift.
* I untaped the cable and flexed/shook/bent it (a lot) to see if there was perhaps a short somewhere....this showed no problems whatsoever.
* I definitely checked the connections pretty thoroughly to see if there were any loose connections and found no problems whatsoever.
* I tried a different cable in the same locations.  This DID show up with the same exact problem, and again ONLY when someone was walking in the "close but not touching/moving the cable" location. 
* The two SD16 boxes were jumped one to the other (not on separate cables to the mixer).
* Most (if not all) of the time the pop/snap happened, no one was touching the console, stage boxes, speakers, gear plugged in, etc.  In fact the when I finally figured out where that "zone" was, and could consistently make the problem happen, I was the only person in the venue, and I was 30' from the board, stage, gear, etc. and 2'-5' from the cable.

And remember, when I moved my mix position, and rerouted the same exact cable along a different location (next to a wall), I had no issues whatsoever. 

I "fixed the problem", but I don't think I really understand exactly what the problem was. 

d.


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Brian Jojade

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Re: Static Cat5e STP????
« Reply #7 on: March 13, 2019, 12:53:00 am »

"I "fixed the problem", but I don't think I really understand exactly what the problem was."

Which sounds like how most problems end up being solved. lol
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Brian Jojade

Chris Hindle

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Re: Static Cat5e STP????
« Reply #8 on: March 13, 2019, 08:02:44 am »



I "fixed the problem", but I don't think I really understand exactly what the problem was. 

d.
You did an impressive list of trouble-shooting.
If it looks like a duck, and quacks like a duck......
Chris.
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Ya, Whatever. Just throw a '57 on it, and get off my stage.

Dan Mortensen

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Re: Static Cat5e STP????
« Reply #9 on: March 13, 2019, 04:27:50 pm »

OK, some more details and info for everyone to see if we can figure this one out for real.

First of all, I have not had a chance to test continuity shell to shell, but will as soon as I'm able.  This will probably be the most important detail to know of course.

Second, understand that I have used this exact same rig/gear/setup in this exact venue/location a few times with no problems.  I've also used this same console/cable/stage boxes/speakers a bunch of other places with no problems.

Third, when I "fixed" this problem the other night, I moved everything, using the same cable, to another location (away from the carpet) and had no problems whatsoever for three performances and some other rehearsals.

So, now some random other facts and details:
* The cable is about a year old, has not been used heavily, has always been stored/kept on a reel, and is/should be in very good condition.  This is not something that gets a lot of use/abuse.
* The cable is 150' long.
* The mix position was about 75' from the stage boxes and speakers.
* The cable ran along a wooden floor, and was taped down along the edge of the carpet about 50' of the way.
* The ONLY place where someone walking close to it that caused the pop/snap was about midway between the mix position and stage boxes.  No one stepped on the cable.  The zone in question was about 2'-5' from the cable, and about 12'-15' lengthwise along the cable run.  No other location manifested in a problem, including anywhere close to either end.  Perhaps importantly, that zone included some steps on carpet and also some steps on wood.  It was far enough from any of the gear plugged into either end of the cable as to not cause them to move/shake/shift.
* I untaped the cable and flexed/shook/bent it (a lot) to see if there was perhaps a short somewhere....this showed no problems whatsoever.
* I definitely checked the connections pretty thoroughly to see if there were any loose connections and found no problems whatsoever.
* I tried a different cable in the same locations.  This DID show up with the same exact problem, and again ONLY when someone was walking in the "close but not touching/moving the cable" location. 
* The two SD16 boxes were jumped one to the other (not on separate cables to the mixer).
* Most (if not all) of the time the pop/snap happened, no one was touching the console, stage boxes, speakers, gear plugged in, etc.  In fact the when I finally figured out where that "zone" was, and could consistently make the problem happen, I was the only person in the venue, and I was 30' from the board, stage, gear, etc. and 2'-5' from the cable.

And remember, when I moved my mix position, and rerouted the same exact cable along a different location (next to a wall), I had no issues whatsoever. 

I "fixed the problem", but I don't think I really understand exactly what the problem was. 

d.

I agree that you did a good job of troubleshooting.

Some more questions:

How does AC get from stage to FOH?

Was the second cable that exhibited the same problem in the same place the same kind of cable or something else?

Was there another spot in the run that had a similar combination of carpet/wood?

It's difficult to comprehend how a static-creating area 2'-5' from a cable can create a problem that spans that distance.

Did you try reversing the cable ends so a different part of the cable was next to the trouble zone?

I'm grasping at straws, just as you are.
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