Strobe lights knock connection off? Weird

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This topic contains 11 replies, has 5 voices, and was last updated by Profile photo of ahjeff ahjeff 9 years, 11 months ago.

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  • #22774
    Profile photo of lawbass61
    lawbass61
    Participant

    Working a high school show this week. Last night in tech rehearsal, they used strobe lights for one song. When the fired up, the connection between the T112 and the IDR48 was lost. It happened twice. What is weird is that the T112 and the IDR are on different electrical circuits, and both are on uninterruptible power supplies? Any ideas?

    Jonathan Wade
    Suburban Legend Audio

    #28223
    Profile photo of ahjeff
    ahjeff
    Moderator

    Hi Jonathan

    There are a number of possible causes for a problem like this. Here are a few ideas:

    Try looking in the Touch Screen event logs. Before a disconnection, are there ACE QoS warnings?

    How long and what type of cable are you using for your ACE link? A cheap or faulty strobe light could emit a lot of rogue radio energy, which with unshielded or cheap cables, could cause electrical interference on the Ethernet lines, which in turn could cause a disconnection. We have a list of recommended cables that we have tested for use with ACE here http://www.allen-heath.com/ilive/system/cables. These have been tested at 120 meters with no errors reported even with 2 kV mains line transients being injected into the rack or surface PSU. Even with good cable, a damaged or poorly fitted RJ45 connector on the cable can have a significant impact on the noise susceptibility of the ACE link.

    Proximity of power cables to a data cable can also be important. If you have a noisy, high current power line running parallel to an Ethernet cable, this will increase the chance of noise on the power line affecting the Ethernet link. In this case it does not matter whether the power line is on a separate circuit.

    In general, the connection should be fine even with quite a few errors; perhaps even 10s of errors per second could be OK, but you might notice a meter stutter, or sluggish response from the control surface. Did you notice this kind of symptom at the show?

    If you are in this sort of situation again, you could try having a look in the Mixer Preferences page of the Mix Rack Setup screen. Select ‘Port A/B Setup’, then press the ‘Advanced’ button at the bottom of the Port A ACE area. You will then see various counters that are updated every second. There is one counter (Error Count 1, Error Count 2 is only relevant if you are using an ACE Option Card) showing you the number of errors per second for each of surface and rack (scroll down to see the second one). If these counts are high, this means that there is some problem with the ACE link that could cause a disconnection.

    Hope this helps.

    Cheers

    – Jeff, A&H

    #28224
    Profile photo of zblebt
    zblebt
    Participant

    Are you using Shieldet UTP? strobe light can emit lot of bad, electrical “noise”.

    Edit: he was faster. :)
    iDR 48
    T112
    waiting for iPad2
    and M-Dante

    #28225
    Profile photo of jimvoyager
    jimvoyager
    Participant

    Hey Jeff, thanks for all that background info, it makes understanding the system easier in terms of sorting a cat5 cable issue.
    For the ‘badly fitted connector’ scenario, I have a cable tester that just checks continuity across the 4 pairs. Is this adequate to find a fault or are we needing something a bit more involved to check a cable….. Say something that measures the impedance across the cable and fitted connectors?
    My system currently works fine in this respect but I’m always aware that it’s possible to be on the limit without knowing, and then an extra long cable or other variant pushes your luck too far. And then it’s Game over!
    Jim

    R72 & IDR32

    #28240
    Profile photo of lawbass61
    lawbass61
    Participant

    Ok, in follow up since I was the OP, thought I would let you all know what I learned. We switched the strobe’s power to a completely different room to ensure it was as far away as possible. However, even though the strobe did not kick off the system again, I started having problems with losing connection throughout the whole show.
    I therefore believe that the cable is the culprit, not the lights. I must say it was a long weekend constantly rebooting the system. The major slow part was that once it booted, it took forever to get the keyboard screen to come up to enter the logon password for the system. I am talking 30 to 45 seconds after touching the touchscreen to have the keyboard pop up. I am going to send the event log to A & H this week to see if there is anything else going on.

    I have been using some cable not on the approved list CAT5e cable. I am therefore going to bite the bullet and buy something better. I do have two questions before doing so. First, I cannot seem to find a retailer that sells either of the two cables on the approved list here in the US. Can anyone direct me to a retailer who carries either of those? Second, is there any update to the approved list since A & H has had this product out for a longer period of time. It sure would be nice to have a wider variety of cables that we can choose from. Thanks

    Jonathan Wade
    Suburban Legend Audio

    #28241
    Profile photo of lawbass61
    lawbass61
    Participant

    Oh, Jeff, the answer to your question is yes. The system was very sluggish. Even when the connection was not lost, I noted several instances during the evening when the T112 “froze”. Specifically, I noted that the meters would occasionally stop updating constantly and the meters would be frozen in place for 2-3 seconds. It was a long night.

    Jonathan Wade
    Suburban Legend Audio

    #28245
    Profile photo of kentlowt
    kentlowt
    Participant

    We got our cable from Full Compass.

    112T/IDR48/IDR16

    #28248
    Profile photo of ahjeff
    ahjeff
    Moderator

    Hi Jim

    A simple continuity tester will not identify subtle faults in the cable like a badly fitted connector. For this you need a more sophisticated cable analyser, but these are expensive. You can get some reassurance that you are not on the edge of the connection failing from the ACE QoS indicators. On the system info window on the touch screen (the page with the clock on it), you should see traffic lights associated with the ACE link. If these ever change to orange or red, this means you have experienced a few errors on the ACE link. These should also be reported in the touch screen event log. There isn’t that big a line between ‘working perfectly’ and ‘starting to go wrong’ with Ethernet, but if you never see any errors on the ACE link, you can be reasonably confident that you have a solid setup. If the lights are going orange or red, you can look at the exact error rate (see my earlier post). If the reading is rarely zero, this would be a fairly strong indicator that there is an issue with your cable.

    Jonathan; Moving the strobe light to be powered from a different room does not necessarily rule it out as the cause of the problem, as it could still be emitting a lot of radio energy. If you don’t get the kind of sluggishness and dropouts at other venues, then this of course points to some issue with equipment at this particular venue. It could also be a combination of two problems that by themselves do not cause an issue, for example a slightly substandard cable, along with a noisy piece of lighting equipment.
    This information doesn’t help you much, but my main point is that although I would always recommend using a good quality cable, I can’t predict whether or not a better cable will solve this particular issue that you are having.

    Cheers

    – Jeff, A&H

    #28255
    Profile photo of lawbass61
    lawbass61
    Participant

    Jeff, just out of curiosity would this tester find a problem with the CAT5e cables we need to be using?

    http://pro-audio-warehouse.com/pal-1543.html

    Jonathan Wade
    Suburban Legend Audio

    #28263
    Profile photo of ahjeff
    ahjeff
    Moderator

    Hi Jonathan

    That tester looks like it just checks for continuity, but does so between incorrect wire combinations to identify a cable that has been wired up the wrong way round. I was thinking of something more like this http://www.flukenetworks.com/datacom-cabling/copper-testing/dtx-cableanalyzer-series, but somehow I don’t think the average user is going to want to fork out for that! This is part of the reason we have an approved cable list, as it is almost impossible for the end user to predict how well a particular cable will work. If you want to try out some other cable, the cheap solution is to soak test it, to see if any errors are reported by the software when your system is running in your target venue. If you can do this with high power and/or noisy equipment like strobe lights running, this sort of test should give you a good level of confidence that the system will work well in the real show.

    In general, you should not encounter any problems due to electrical interference or noise if you are using a good cable. The fact that you had some problems in this particular venue indicates to me that there was something wrong, but as before, I can’t predict whether a better cable will solve this particular problem.

    Hope this helps

    – Jeff, A&H

    #28287
    Profile photo of lawbass61
    lawbass61
    Participant

    Ok, Jeff, now you have me curious. What pray tell is a “soak test”? My mind says you mean put the whole cable in water while the ends are connected to the control surface and the IDR, but that is perhaps too literal. By the way, there are some old posts mentioning Belden 1305A as an approved cable, but its not on the list. Is that cable in fact ok? The reason I ask is that while I am waiting for a Proplex cable to arrive, I have a good source for Belden 1305A that I am thinking about getting as a backup.

    Jonathan Wade
    Suburban Legend Audio

    #28289
    Profile photo of ahjeff
    ahjeff
    Moderator

    Hi Jonathan

    By ‘soak test’, I just mean running the system for a period of time, to reassure yourself that it is working properly. If you can have a system running for a couple of hours during a period that a problem would not matter, and experience no problems, this will give you more confidence that you will not get problems during the show, when it does matter. Soak testing is a good way to discover problems that do not have an easily measurable or predictable cause.

    The Belden 1305A cable does have good performance, but our system does not pass EMI regulations using unshielded cables, so we cannot recommend it.

    Cheers

    – Jeff, A&H

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