Alesis MultiMix Hum
The following information addresses how to repair a power supply issue with the Alesis MultiMix. I first noticed the problem about a 7 months ago.
Symptoms are as follows:
- Clip & Sig LED are on solid (FX section)
- XLR Inputs hum
The XLR input hum is the worst problem in my case. So after some Googling and reading, problem is that 2 of the power supply capacitors are blown. To change the capacitors is fairly simple. First thing is to remove the screws on the bottom and the back of the mixer as shown below.
Now that the rear plate is loose, disconnect the black 8 pin connector to the power supply, then disconnect the 2 pin SPDIF connection to the main bored on the right.
There should be enough room to get a fillips screw driver in there and remove the power supply bored. But first the connecting wires need to be disconnected.
From left to right:
- Power Connector
- Power on/off switch
- Phantom Power switch
- Main power to the the mixer
As many posts online have said, both capacitors are going to need changing at the same time. Here are the specs of the capacitors. Voltage doesn’t matter to much.
Right Capacitor – 1000uf @ 35V
Left Capacitor – 2200uf @ 35V
My local electronics shop had the right capacitor in stock but I had to use a 50V cap on the left one. It was a little bit bigger so my new cap sits a little sideways on the bored.
That is it. You have now successfully change the 2 capacitors causing the hum in your mixer. Follow these steps backwards to put your mixer back together.  Be sure to evenly apply pressure  to the heat sink. Also, when putting the base plate back in, be patient, it will slid in together easily.