Thursday, December 29, 2011

Eurodesk MX2442A Restoration: Part 1 - Disassembly

The next step was my favorite, and probably easiest; the Disassembly. I brought the board up to my kitchen table, the only place I had enough room, and even that's not enough! I started by removing each fader and knob one by one and placing them in a container. I thought that would be fast, but you soon realize there are more knobs and faders than you think! Finally I got everything off.
Then it was time to take the plastic trim panels off the sides and the small machine screws holding the circuit boards to the faceplate. I started left to right taking all the #1 screws out, and was having no problems. THEN I got to the screws by the master section. NONE of them would come out. All the screws started stripping. I finally did get one out, and I saw it wasn't a machine screw, but a self-tapping screw; like you'd use in wood. Like this:
So right there a red-flag went off. Why were every one of the screws a machine screw that threaded in nice and easy, then have a random self-tapping screw? Something was wrong.

So then I stood the unit on end to remove the screws holding the top of the board to the chassis. I put the mixer back on the table and the unit slid out of the chassis. So now I can see the back of the circuit boards, and I noticed this:

There were a total of 5 connectors unplugged! So basically channels 1-16 weren't getting any power. My first thought was, "That's it!! I am gonna plug these back in and it will work!". No. I did get some normal functionality back when I turned it on, but still nothing on the output or in the headphones. I can now get signal IN on channels 1-16, so that is a start. I also tried putting an AUX source in through the tape input, and I can hear it through the headphone jack, but it is extremely distorted. So at this point it is time to do two things. 1) get the screws out holding in the master section, and 2) start troubleshooting.

Next up, part 2 - troubleshooting.

Wednesday, December 28, 2011

Eurodesk MX2442A Restoration: Prologue

During my daily cruise through the Craigslist, Musical Instruments section, I stumbled upon an ad for a 12 year old Eurodesk MX2442A. The seller was asking $50, because the mixer no longer had any output on the mains and they didn't want to invest in fixing it.

I can completely relate to the cost of repair / replacement. She might have spent a few hundred dollars in repair for a mixing board that is only worth maybe that in working condition, so it is a slippery slope. With that being said however, I have had decent luck in repairing Pro-Audio equipment in the past, especially pieces that are out of warranty and aren't a necessity to the studio. In this case, the mixing board was definitely NOT a necessity; more of a side-project. So my confidence was high, having just repaired an Alesis RA-300 studio power amp (also bought off craigslist), I thought I'd give this a go.

Now some background on the unit. It is a 24 channel Behringer Eurodesk MX2442A. It has 16 XLR inputs, 4 stereo inputs, 4 sub-groups and a Main out. It came with an external rack-mountable power supply and the original owner's manual (which has no value as far as repairs go). The chassis is in good shape and all the faders seem smooth. The knobs and plastic pieces are a bit worn, but if the repair is successful, they can be replaced for little cost and really give the board a fresh look.

So here is the initial diagnosis. I set up the board on a keyboard stand I had in the control room, plugged in the power supply and flipped the switch. All that happened was the clip and signal lights (red and green respectively) for channels 17-24 stayed illuminated, no matter what buttons were pressed, or knobs turned. Next I plugged in a microphone to channel 1 to see if I could get any signal on the channel. Nothing. Moved it down the line from channel 1 to 2 and repeat. Nothing. 3 to 4; nothing, and so on down the line. So no signal on any mic channel. So next step is to open this thing up and take a look at what surprises await inside.