I found a solution for my problem. I have Alesis Multimix FireWire 16. So the same humming and buzzing problem with the peak light always on. I followed a very simple tip from a post on YouTube (Just type in Google "Alesis capacitor repair").
Here's what you do:
1. unscrew the bottom cover panel of the unit (about 10 screws total),
2. detatchthe bottom part of the unit from the top part unplugging about 5 or 6 different cables.
3. unscrew the capacitor/power circuit board, that is attached to the inside surface of the bottom panel (its green and is about 4 by 5 inches. can't miss it - its the only one there)
4. on the board you'll see 3 black cyllindrical filter capacitors. at least one of them will be blown. in my case the 1000mf had its gasket completely bulged out.
5. replace both 1000 and 2000 filter capacitors. if you replace only one - it might not solve the problem.
6.re-assemble the unit.
This should do it. I hope this helps.