Members jlb Posted August 27, 2012 Members Share Posted August 27, 2012 I showed up to a gig yesterday and all power outlets available were 15 amp GFI's. About 5 hours into the gig one of my amp channels/mains shuts down (ITech 6000). I go to my amp monitoring page and see the load impedance fluctuating between 200 and 250ohms! Can someone help me understand the chain of events leading up to this failure? Link to comment Share on other sites More sharing options...
CMS Author Craig Vecchione Posted August 27, 2012 CMS Author Share Posted August 27, 2012 The GFCI has nothing to do with this. Check the cables and speakers on that channel. Did you switch the speakers on that amp to see if the problem "follows" it to the other amp channel? Is there a crossover network inside the speaker? Link to comment Share on other sites More sharing options...
Members jlb Posted August 27, 2012 Author Members Share Posted August 27, 2012 I contacted Kevin at Crown and his first question was "was the amp running of GFCI?". He said this was the problem, but did not really get into any detail. Link to comment Share on other sites More sharing options...
Members Vinny D Posted August 27, 2012 Members Share Posted August 27, 2012 So did the GFCI circuit trip or did just one channel on the amp shut down? Link to comment Share on other sites More sharing options...
Members jlb Posted August 27, 2012 Author Members Share Posted August 27, 2012 The channel running my tops shut down right in the middle of the 6th band. I have the amp running now on the same tops with the same cables. It has been running for 3 hours with no issues. Link to comment Share on other sites More sharing options...
CMS Author Craig Vecchione Posted August 27, 2012 CMS Author Share Posted August 27, 2012 Give them a call back and ask for an actual explanation...as well as a viable workaround when you need to use the amp outdoors or in any other location where a GFCI-protected circuit is required. It's not as if either GFCI or switching supply are new technology. Link to comment Share on other sites More sharing options...
Members Vinny D Posted August 27, 2012 Members Share Posted August 27, 2012 Did the Itech reset on the gig when you shut it down & powered it back up again? Link to comment Share on other sites More sharing options...
Members jlb Posted August 27, 2012 Author Members Share Posted August 27, 2012 No it did not. I plugged a new 4000 in and the same thing happened. Link to comment Share on other sites More sharing options...
Members Vinny D Posted August 27, 2012 Members Share Posted August 27, 2012 By any chance did you reset the GFCI circuit? (was this a breaker or outlet?)I am asking because I myself am not a fan of running my gear on GFCI circuits, it seems everytime I have an issue it involves a GFCI circuit.From having musicians stage amps tripping to having my QSC PLX amps often trip them on power up...And by the way...GFCI devices still lead the pack in defective returns that my company deals with every year. Link to comment Share on other sites More sharing options...
Members jlb Posted August 27, 2012 Author Members Share Posted August 27, 2012 This was an outlet. I did not have access to breaker. There were 3 dedicated separate circuit/outlets. One for my amps and one for backline/lights. Link to comment Share on other sites More sharing options...
Members Vinny D Posted August 27, 2012 Members Share Posted August 27, 2012 I would have tripped the GFCI outlet (push to test button) and reset it to see if it made a difference. Link to comment Share on other sites More sharing options...
CMS Author Craig Vecchione Posted August 27, 2012 CMS Author Share Posted August 27, 2012 I certainly agree about GFCI's failing at an alarming rate (I just replaced one this weekend), but I've also got a PLX and have never had problems with it tripping a GFCI. Link to comment Share on other sites More sharing options...
Members Vinny D Posted August 27, 2012 Members Share Posted August 27, 2012 I certainly agree about GFCI's failing at an alarming rate (I just replaced one this weekend), but I've also got a PLX and have never had problems with it tripping a GFCI. I believe my issue with the PLX tripping the GFCI is a isolated instance.It happens in the same venue...on the same GFCI outlet, when I move to another GFCI outlet in the same venue I never have an issue.But I still amuse myself everytime I go there and try it just for fun anyway! Link to comment Share on other sites More sharing options...
Members jlb Posted August 27, 2012 Author Members Share Posted August 27, 2012 In my case I did not trip the GFI. Link to comment Share on other sites More sharing options...
Members Vinny D Posted August 27, 2012 Members Share Posted August 27, 2012 In my case I did not trip the GFI. I understand you didn't trip it, I just suggested that you should have tripped it and reset it to see if it corrected the issue you were having.Most GFCI outlets I find at outdoor venues are so corroded the push to test buttons don't work anyway. Link to comment Share on other sites More sharing options...
Members spottyaudio Posted August 27, 2012 Members Share Posted August 27, 2012 had a similar situation with rented genny and spider boxes where the left side of the line array was on its own 20a circuit and everytime someone would sing loud into the mic, it would trip. the lighting guy, with not much to do, ran back and forth resetting it quite a lot. i understand why its required in certain places, but man, i dont like it. glad your crown amps both work great still, something to be said for quick and well researched fault protection inside those amps. Link to comment Share on other sites More sharing options...
Members Vinny D Posted August 27, 2012 Members Share Posted August 27, 2012 had a similar situation with rented genny and spider boxes where the left side of the line array was on its own 20a circuit and everytime someone would sing loud into the mic, it would trip. The outdoor gig I did last week had the EXACT same thing happen, whenever the singer belted out a loud vocal passage it would trip my IT8000 that was on a 20a GFCI breaker. The amp is actually limited to 600w RMS @ 8ohms and the peak RMS is set at 1600w RMS @ 8ohms.The breaker never should have tripped...but it did, everytime I couldn't ride the channel fader fast enough! Link to comment Share on other sites More sharing options...
Members agedhorse Posted August 27, 2012 Members Share Posted August 27, 2012 Two different problems, one is the tripping of a GFCI breaker and the other is an amplifier protection problem. Tripping of GFCI protection can be from one of 3 things... an actual ground fault, an overcurrent fault or a faulty GFCI. Tripping of the amp's protection has nothing to do with the GFCI, it's just a differential current sensor on a pair of wires and a mechanical switch. I really don't think it had anything to do with the GFCI, but by chance could you have had a fault such as an intermittent speaker cable or a failing speaker? I think this needs a more thorough discussion with Crown regarding what actually happened, and did the new 4000 that failed give identical error messages? Did you by chance use it on the same speaker load on the same channel? Link to comment Share on other sites More sharing options...
Members jlb Posted August 27, 2012 Author Members Share Posted August 27, 2012 When I hooked up the new 4000 same channel, same preset, it was reading exactly the same as the 6000. What I'm not understanding, among many other things is why the other channel running the subs was not acting this way. Edit : I have been running the system with the same cables, cabinets, and amp for 9 hours with no errors or issues. Link to comment Share on other sites More sharing options...
Members agedhorse Posted August 27, 2012 Members Share Posted August 27, 2012 When I hooked up the new 4000 same channel, same preset, it was reading exactly the same as the 6000. What I'm not understanding, among many other things is why the other channel running the subs was not acting this way. Maybe because there was an actual load fault like the amp was telling you? You need to eliminate this as a possibility (and it's the most likely possibility IMO at this point) Link to comment Share on other sites More sharing options...
Members jlb Posted August 27, 2012 Author Members Share Posted August 27, 2012 Maybe because there was an actual load fault like the amp was telling you? You need to eliminate this as a possibility (and it's the most likely possibility IMO at this point) How would you suggest I do this? Are you saying that my cabinets or cables may be damaged? The cables have tested ok. Link to comment Share on other sites More sharing options...
Members agedhorse Posted August 27, 2012 Members Share Posted August 27, 2012 How would you suggest I do this? Are you saying that my cabinets or cables may be damaged? The cables have tested ok. Yes, check very carefully your cabinets for an inop. driver leaving the crossover operating into an unterminated load. It can cause ringing and varying impedance which can be fatal to some class D implimentations. That's why many have this kind of protection. It could also be a defective crossover or even an incorrectly designed zobel compmensating network. What cabinet(s) were connected to the channel? Link to comment Share on other sites More sharing options...
Members Mutha Goose Posted August 27, 2012 Members Share Posted August 27, 2012 ... even an incorrectly designed zobel compmensating network. I am very curious as to your thoughts on this. A Zobel network should be in the amplifier, not the load. And if he is having oscillations of this nature, he would have a bigger problem. Why are you thinking this could be a contributor? Link to comment Share on other sites More sharing options...
Members jlb Posted August 27, 2012 Author Members Share Posted August 27, 2012 Yes, check very carefully your cabinets for an inop. driver leaving the crossover operating into an unterminated load. It can cause ringing and varying impedance which can be fatal to some class D implimentations. That's why many have this kind of protection. It could also be a defective crossover or even an incorrectly designed zobel compmensating network. What cabinet(s) were connected to the channel? They are SRX 715's. My limiters are set very conservative. 800WRMS for both drivers and 100v Peak limiter. I was getting about 2db of limiting at times during the show, but very infrequently. Like said in previous post I have been running my system all day, non stop with no errors. Loads have been steady between 4-6ohms. Granted it is not a live situation, but the cabinets sound fine. Link to comment Share on other sites More sharing options...
Members agedhorse Posted August 27, 2012 Members Share Posted August 27, 2012 I am very curious as to your thoughts on this. A Zobel network should be in the amplifier, not the load. And if he is having oscillations of this nature, he would have a bigger problem. Why are you thinking this could be a contributor? There are also Zobel networks that are used for driver impedance compensation (for crossover linearization), same name, same basic function but different application. The reason for the problem, especially with class D is that they can store energy and under some conditions act like a tank circuit with the other components (including the class D output reconstruction filter) to cause ringing of the class D carrier. I have seen this a few times and developed a fix for one of our competitor's cabinets that was shutting down a variety of class D bass amps. Awkward situation to say the least. Involves adding additional R damping to the zobel. Not saying this IS the problem, but is something to verify that it's not. Link to comment Share on other sites More sharing options...
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