Fixing a Behringer MX8000 desk

Got my mixing desk back from a long term loan and unfortunately  it doesn’t work anymore :/

On power up, there’s plenty of hum coming out of it, flashing input and solo leds, scratchy pots and faders, silent channels, etc….

I guess it’s a power issue, either in the PSU or in the desk itself. Looking at the components, it’s packed with cheap chinese electrolytics capacitors, but apart from those the rest is standard thru-hole resistors, ceramic or mylar caps with NJM 4580 SIP package dual op-amps (still available at mouser).

So my best bet is that some electro caps have rendered their last breath and shorted the rails…

The adventure begins….

MX8000_1

4 thoughts on “Fixing a Behringer MX8000 desk

  1. Steve

    I’ve worked on a few of these Behringer boards with the ribbon interconnects. The ribbon cables do get old and for whatever reason they do fail (maybe they oxidize, causing poor connections at the IDC connectors? In any case the insulation becomes brittle).

    I certainly recommend you give them all a good wiggle with the power on and all channels up to see how intermittent they might have become.

    Reply
  2. Terence Hacke® Post author

    Hi Steve,

    I’ve looked at the connectors but they are ok I think. PSU is ok too .Problem seems more important than intermittent connections.

    I’ve got a big 15V P/P square wave coming from the main board when I press the mix B button on the Phones. Changes frequency as i turn the phone level pot. Makes a great oscillator 🙂

    Also the mono inputs (Right channel) of External and 2 track inputs don’t work. Left channel is ok.

    So far I’ve disconnected the channels boards to try locate the issue so it’s pretty sure the problem lies on the Main board but where?…

    Reply
  3. Lorne in Canada

    A gentle pass with a hot air gun at about 275 degrees might catch any brittle connect points.
    Brought my nephews emu interface up with that alone.

    Reply
  4. Scott Stevenz

    I bought one of these dead for 80$ a few years ago. I thought I would teach myself electronics repair, and this was one of my first projects. LOL . It took me a couple of months , being a complete novice, to rebuild the power supply. I didnt even know how to use a voltmeter, but eventually I did get the psu to work! After that channels 1-16 seemed to work for the most part, but 17-24 werre dead, giving the red and green lights of death across those 8 channels. It sat for about 3 years, unused. In the meantime, I completed my next project, and brought an emu emax II back from dead. Since then I have fixed countless synths and samplers.
    All the while been thinking about the dead 8 channels on the mx 8000, and doing more research the last week. So tonight I cracked it open, expecting to see a loose ribbon cable . There was nothing obvious wrong . So I started with the ribbon cables attached to the channel 17-24 board, cut the glue off the connectors , and pried them off. Then I sprayed deoxit on all the connectors. When I wiggled the middle ribbon cable at first, the red and green lights would go on and off intermittantly, but after I sprayed the connectors they stayed lit, still no sound. Then I noticed the power connector that goes to the dead board was unplugged , where the power comes into the board. I thought that would cure it, but it did not. There was a nasty old dead bee underneath the plug, I scraped it out. Then I proceeded to pull off the ribbon cables that connect the channel boards and jack boards, and deoxit sprayed the connectors. I followed this by unplugging the power connector where it goes into channel 17-24 board and sprayed deoxit, then replugged it. All of a sudden I had sound on the dead channels! After that I tested all channels and found a few channels across the board that are too soft or somehow glitchy patchwise. I called it a night, since it was 4 am and when I get tired, I start making things worse. So tomorrow night Im going to scrape all of the glue off of all remaining ribbon connectors, and spray deoxit on all of them, Then I will reglue them all with electronics grade silicone, and put the damned thing back together! Hoping I can get it close to 100% ! Then I just have to find room for this monster in my studio!

    Reply

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