Quite a while ago one of my Mackie MR8 monitors started making a constant hum, similar to a 60 cycle hum but higher pitched. It doesn't matter if I have anything plugged into the monitor or not, it's just a constant noise, rendering the monitor unusable.
I opened it up and noticed that two of the capacitors are swelling at the top, looking like they're going to leak soon. I know that this certainly isn't good, but I don't know if this would be the cause of the problem I'm having, if so it wouldn't be difficult for me to repair, soldering to PCB is easy as hell. But I lack the troubleshooting skills to pinpoint a certain component, and I have no idea what would lead to the noise, all of the connections, namely the grounds, are intact and looking good.
So...if anybody has an idea or a possible solution, please let me know. There is no Mackie repair center close to me so it's not convenient at all for me to drop it off somewhere, and since I am competent at soldering and have modded a pre-amp before I would like to replace the bad component(s) myself.
I'd change those caps first and see if that helps. Looking at the block schematic there's a few filters around the place, if the caps in the filters aren't working properly that could maybe result in hum. Also, double check all the cables, connectors, joins and grounds etc on the input, as there's a differential amp there, any small amount of noise or hum that manages to creep in on that input will become very significant on the other side and could be where the problem is.