ElectroVoice CPS 4.5 series faulty protect circuit |
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TPTech
New Member Joined: 29 March 2021 Status: Offline Points: 2 |
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Posted: 29 March 2021 at 9:08am |
Hi There! Over the last week we had some weird glitch happen over the site that sent the amps into a weird pattern of popping noises/white noise out the speaker, and the amps constantly going in to protect mode. After resetting the system, everything went back to behaving normally apart from 2 amps. Even with no load and no input, the amp is still popping, going in to protect, rinse and repeat. 1x EV CPS 4.5 on channel 2 1x EV CPS 4.5 on channel 3+4 On the first amp, using the selector switch on the back, I put the channels in to bridge mode and both channel 1+2 started to go into protect. Swtiching it back stopped channel 1 going in to protect again. When powered up, you can hear the relay on the protect circuit firing every few seconds. I'm relativly new to the more detailed amp troubleshooting so I am wondering if any one here has some advice/experienced something similar? I have had a look around on this forum and I do have the schematic for the EV Q1212 series that was posted but obviously thats not the same amp! I have had a look through the manual from EV as well and it doesn't mention anything outside of the usual operation of the protect circuit. Many thanks! Edited by TPTech - 29 March 2021 at 9:09am |
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studio45
Old Croc Joined: 16 October 2007 Location: United Kingdom Status: Offline Points: 3863 |
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Sounds like you may have had a mains supply overvoltage event, if every amp at your site was affected. So I'd start by looking at what might be damaged by overvoltage in the amp...although that's almost every component!
Most of the time, protection circuits operate when they have sensed DC at the amp outputs, this is usually caused by a shorted output MOSFET or transistor. This is also a common result of overvoltage events.
Try looking at the output of the faulty amps on a scope. A multimeter may not react fast enough to give you a reading on a DC fault before the relay clicks out again. The scope will show any brief spikes of voltage. Or, try metering the output line before the relay. If you see one of the DC rail voltages steady, it's a shorted output device for sure. |
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Studio45 - Repairs & Building Commotion Soundsystem -Mobile PA
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simonp1100
Young Croc Joined: 01 September 2008 Location: Bristol Status: Offline Points: 1103 |
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Sounds like a channel input op-amp fault to me. It could be either one of the channel balanced op-amps or the op-amp that does the bridge signal section. I think a circuit diagram would help you if you can get one.
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