Mackie MCU misbehave

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joaquins

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Feb 25, 2012
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  Hi, I'm here asking for help with a Mackie Control Universal doing strange things.

  The problem is some parts of it acts as it should and some don't. PC conectivity ok, comunicates with logic pro and do some functions correctly. Faders are mostly fine (except one channel follows the master sometimes, you move the master, this channel goes with it), Lights of the mute/solo/rec section work fine, some of the buttoms do, some don't. Panpots are fine and work, but as they change functions and the function selection switches act up sometimes, they do whatever. Other parts of the thing do different functions than it should or trigger without nobody pressing anything.

  I can't get the service manual or schematics (only the PSU but it seems to be fine) and official support doesn't seem to care, they said they had no idea what was going on and missed the missplaced connector all together or something, I don't know the exact story around that as I was just left with the thing with a few comments.

  What's done so far... well, PSU check ok, voltage fine, noise reasonable levels, HF sine-shaped ~100mVpp. But... eye inspection confirmed that somebody had fan before I did, so missplugged the small display on top of the channels and probably burned the controller, as it no longer works, just few segments flickering with no characters at all. After I placed the connector where it should things got better (it was christmas-tree-crazy before). Gave it for fixed, called the owner, tested on the PC and some problems still persists. Some got solved by unplugging the connector all together. I ASSume the problem was there before the missplugged display, or why somebody will take it out and back again in the wrong place???
  µC is shooting data by the busses, some communication is going on back and forth as it interacts correctly with the PC in some functions. Pins going to the, no longer there display shoot data as well so the bus driver going to the display seems fine (looks like a dedicated 3 state line driver IC for the task)

  The working theory was being some wiring problem, but I separated the boards, left with the PSU, motherboard, PC conectivity and pan/rec/mute/solo/select switches PCB, checked all the connections between mother and switches PCB and all were fine and data consistent on both boards while the problem still persists.
  Right now I'm leading to a burned IC (or, let's hope not, individual µC GPIO pins not working) but this thing is filled with muxes and what not as it has a 30 pin µC to drive 2 displays, 9 motorized faders, 9 encoders and a royal bunch of switches and LEDs. So a real pain to debug.

Well, any thoughts are welcomed, and any tips of where should I look for as well!

Thanks in advanced!
JS
 

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