Bear in mind that with some gear the on off switch isn’t directly disconnecting the internal power supply. If you have something with a simple push button for instance that is just sending a signal to the processor or similar to say apply power. In other words the PSU is in circuit even when it’s switched off. Standby on TV’s is an example of this. I’ve got a presonus SL32 and it’s a rocker switch but without delving further I can’t say whether it’s directly switching the mains before it hits the PSU or not?
It sounds like you might have an issue with the wiring and or consumer unit if you’re getting MCB’s tripping when nothing is switched on. If the mixer was plugged into the same socket outlet each time you could have an intermittent fault at that socket that only shows up because you’re physically plugging into it. I doubt very much that mixer fault you describe with the USB is related to this issue. As you say, the mixer boots up and runs so it’s PSU would appear fine. If it was faulty it would trip the breaker each time you switch it on. If it’s an intermittent fault in the PSU that wouldn’t manifest itself with a desk working but the USB port not working I wouldn’t think. You said the initial issue arose when you plugged in a DJ mixer? I’d be looking at that as the likely candidate as the fault developed when you plugged it in (or switched it on). Again, it could be an intermittent fault and it’s by coincidence more than anything that you’re thinking it’s the Presonus.
Sound obvious but have you checked all sockets etc are in good shape? No floppy plugs or stiff switches? Other plugs are securely plugged in? Beyond that it’s process of elimination.
Firstly I’d leave everything physically unplugged then plug in something like a radio alarm or other device that can be left on (and gives a visual indication if it’s working) into the outlet you suspect of being faulty… leave it a day or two and check it’s not going on and off. Then Plug each item back in one at a time until you can replicate the fault. Then assuming the last thing to be plugged in caused it unplug everything bar that item and see if you can replicate the fault again. If you can’t it was caused most likely by one of the other bits of gear and the fault is coming and going.
It might be worth you getting an electrician in to do a test on the wiring and to check the breakers in the board. I’ve seen faulty breakers nuisance trip plenty of times in the past and I’ve also seen them jam on too.
Edit. I just noticed you said the computer was left running… now depending how your place is wired that could have been on the same circuit as everything else. In the UK we use ring mains predominantly for socket outlets and many houses have a ring for upstairs and a ring for down. Sometimes there’s a separate ring for the kitchen as well, it all depends how and when it was wired. It’s still vet common to have the entire house on one ring main. So if you’re on a ring main it’s almost a given that all the sockets in one room are on the same breaker. How many breakers have you got? Do you know which breakers (if more than one) supply which sockets. As I mentioned further up the thread most studio gear is gonna be pulling a pretty small amount of current so overload shouldn’t be an issue. Unless the breaker in the board isn’t the correct size? But even then (giving the UK as an example) the smallest breaker you can get for a consumer unit is 6A which in terms of a small set up is still plenty enough. Voltage will be constant unless you’ve got major supply issues where you are
One more thing…, if you’re on a ring then anything anywhere on that circuit can cause the fault. Depending on your wiring that could be anything in the house including central heating boilers etc. Same on a radial circuit. Any item or device fed from the same breaker can cause it to trip.
Edit edit…
It was the MCB that was tripping and not the RCD? Or is it a combined RCBO or similar? An MCB will trip in the event of an overload occurring. This (in a fault condition) would be caused by either a Live to neutral or live to earth fault with would cause a huge current to be drawn, tripping the breaker. An RCD ‘senses’ the live and neutral and looks for an imbalance in the two currents. So a neutral to earth fault will trip an RCD but not an MCB. Neutral to earth faults can occur in the wiring but also in anything plugged in that uses the earth pin. They’re effectively invisible without an RCD installed (as the Neutral and earth are basically connected on the supply side of the cut out in your house or further back on the supply side) because everything still works as it should…
