Mackie repair

[Improv]

So, I've had two Mackie 1202's (original brick-shaped versions) go bad on me in my lifetime. I'm not complaining, because both went well over 15 years before exhibiting any problems. But both have the same issue... a loud hum that would change in intensity and stereo positioning based on the position of just about every other knob on the board. I imagine is a blow cap or something of that nature?

So, obviously I have little audio circuitry experience here, but plenty of computer circuitry/soldering experience. How easy would it be to identify the culprit and replace a couple parts myself? Or what would most service places charge for this sort of thing? I don't need a complete overhaul or anything, I just want to kill that hum on the main bus! These are very useful little utility boards when they're running quietly.

So just casting my net out for ideas here. Considering the popularity and age of the model, I'm sure others have encountered this... might have a shortcut to a solution. Regardless, thanks for your time.

[amorris]

Hum or Buzz?

Hum would indicate grounding/wiring, Buzz could indicate power supply caps.

Unplug everything and see if any clean audio occurs anywhere. if say the aux outs are clean, then power supply is also.