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Behringer Mixer help

7/30/2003 11:32 PM
Behringer Mixer help
Does anyone know where I can get a schematic for a Behringer MX3282A mixer. This thing lights up like a Christmas tree. It has a seperate power supply. Any help would be greatly appreciated. Thanks all.
7/31/2003 3:54 AM

Dan, if all the peak lights and everything come on, it is almost certain one of the analog power rails is missing. The power supply provides +/- 15 or 18 or something close. If one of those goes away, then all the op amp outputs slam over to the remaining rail and the peak meters just interpret that as a max signal.  
Look at the corners of any op amp in the mixer and see if the volyages are both there. COuld be a connector problem in the umbilicle, or the supply itself has a problem. I think this thing uses three terminal regulators, whatever the next step up from LM317 is.  
On the other hand, I have had to chase down a short across one of those rails out in the mixer. Every chip has a small blue bypass cap mext to it, and if it shorts, then the rail will load down to nothing. Usually a small black hole forms on the part, but not always. It can be a real bear to find it. Separating the sections of PC board can help.
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8/3/2003 1:23 PM

Thanks for the info. I knew when I posted that I was missing the 12VDC supply. Thanks for the explanation of why that would cause it to light up.  
The power supply board has a few open runs and lifted pads from a previous "repair". So I'm trying to figure out what all should be connected.  
Hopefully its just the open runs and not in the board itself. That does sound like a pain in the butt to find. Thanks again.
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