Cheeseweasel Posted November 7, 2010 Share Posted November 7, 2010 Recently a mate of mine asked me to take a look at his Behringer Truth monitors because they both had a fault. When powered on, they were humming very loudly and the clip indicators came on. After having a look inside, I found that a capacitor had exploded inside the built-in amp (on both speakers). So after replacing the caps (I'm confident that I used the right ones), I turned one on with nothing connected to the input - it hummed for a couple of secs with the clip indicator on, then the same cap exploded with a pop. I guess the blown caps were a symptom of some other problem, rather than the cause. The fact that both of the speakers have gone suggests to me that they were fed a very high level at some point which knackered something inside. Just wondered if anyone else had come across the same fault by any chance and knows what the problem is? (No I didn't put the cap in backwards!) Link to comment Share on other sites More sharing options...
Simon Lewis Posted November 7, 2010 Share Posted November 7, 2010 I wouldn't want to appear unhelpful, but you can't really mend stuff if you do not understand why it blew up... Link to comment Share on other sites More sharing options...
boatman Posted November 7, 2010 Share Posted November 7, 2010 .... (No I didn't put the cap in backwards!) Are you sure? As the cap has exploded twice, it would be worth measuring the voltage on the PCB before fitting a new one. That way you would be sure of the correct rating and polarity. Link to comment Share on other sites More sharing options...
Cheeseweasel Posted November 7, 2010 Author Share Posted November 7, 2010 I wouldn't want to appear unhelpful, but you can't really mend stuff if you do not understand why it blew up... Hence my asking A concurrent post has been automatically merged from this point on. .... (No I didn't put the cap in backwards!) Are you sure? As the cap has exploded twice, it would be worth measuring the voltage on the PCB before fitting a new one. That way you would be sure of the correct rating and polarity. Cheers, might be worth a look. However, unless the board is marked up wrong, I definitely put it in the right way round (the hole for the negative leg is clearly marked). They are also the correct type and rating (I got pretty used to ordering in components when I worked at a desk factory). And since the original factory-fitted caps blew up too, I don't think they are the source of the problem. Tbh, I was asking on the off-chance that someone else had encountered this problem, as these things generally affect all of a particular batch or model. I'm not going to spend loads of time testing stuff and fumbling through the problem, because it will take me ages to fix it and it was really just a passing favour to this guy ("yeah I'll change the blown caps on your speakers, no worries!"). Link to comment Share on other sites More sharing options...
DrV Posted November 8, 2010 Share Posted November 8, 2010 If you are talking about reservoir caps then a possibility would be that the rectifier is faulty and placing raw AC across them. I'd expect a fuse to blow though if the correct value is fitted. Er, or that the units are set for 115v and being fed 230! Dave Link to comment Share on other sites More sharing options...
Cheeseweasel Posted November 8, 2010 Author Share Posted November 8, 2010 If you are talking about reservoir caps then a possibility would be that the rectifier is faulty and placing raw AC across them. I'd expect a fuse to blow though if the correct value is fitted. Er, or that the units are set for 115v and being fed 230! Dave Thanks, I had a similar thought, that part of the power supply was faulty and feeding mains AC into the audio circuitry somehow. Would certainly explain the loud mains hum and cap blowing up after 2 secs. A few people on other forums have reported faulty rectifiers on these speakers, so this could well be the problem. Link to comment Share on other sites More sharing options...
Rob_Beech Posted November 13, 2010 Share Posted November 13, 2010 Can't really be of help but I'd be interested in knowing what the issue is when you find it, I have a pair of these and the now discontinued 2x8 inch "reference" sub in a room at home and I can't fault them at all. If I knew someone getting rid of another of the subs I'd have another. Link to comment Share on other sites More sharing options...
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