Help troubleshoot my audio mixer

Discussion in 'General Electronics Chat' started by jerberson12, Mar 26, 2014.

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  1. jerberson12

    Thread Starter New Member

    Mar 26, 2014
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    I have a Topaz 32 mixing console.
    The regulated power supply has 4 wire output 48v +17v -17v and AGDN
    The mixer has 3 leds lights for each output except -17v led is not turning on. Hence the mixer is not working and no output is coming out

    As per manual if one is not working then there is an issue with your power supply

    Here is what I notice.

    If all the power output is connected to the mixing board, -17v led light is off and mixer will not work.

    If I take out the AGND line, all the led lights turns on and the mixer will work fine.

    Wondering what is wrong
     
  2. crutschow

    Expert

    Mar 14, 2008
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    What do you do with the AGND line from when you "take out the AGND line"?
     
  3. jerberson12

    Thread Starter New Member

    Mar 26, 2014
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    Nothing? Just left it unhook or just hang it there. Wonder what will be the problem for that.

    Im no electrician, just a music guy who wants to fix mixer and make music.
     
  4. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    Can you show me some photo's.

    And disconnecting GND might create other problems. You never disconnect GND, disconnect other lines only.

    If the -17V line goes to 0 when it is connected then there could be a regulator issue or a shorted component in the mixer part.

    Need to see your regulator area.
     
  5. jerberson12

    Thread Starter New Member

    Mar 26, 2014
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    attached is the closeup for the regulated power supply if thats what you need and some are the overall photos of the board

    If there is shorted component, you think rebuilding is a good palce to start?
     
  6. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    start by measuring the output of the psu using a DVM, without a load, then connect the psu to the mixer and check again, if the -17V is disappearing, then trace where it goes to on the mixer.
     
  7. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    That thing is huge. It would take a lot of time to find the fault.

    The -17V regulator needs to be traced.
    If the regulator is OK then it could be a cap or an OPamp

    To check the OP AMPS the mixer PCB (Big (pcb)one screwed to the front panel needs to be removed)
    And to make things worse they will be surface mount I think.

    All you can do I think is check the regulator.

    The third picture is the regulator I believe. Take that board and show some photo's so we can trace the -17V regulator.

    U might need some dummy resistors to load the regulator to check if the regulators work when loaded.

    First lets trace the regulator then check it for heat and overload shutting down issues
     
  8. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    Sorry to disappoint you but that thing is not for beginners repair work.
    It's just too big to trouble shoot by looking at photo's u know.

    It might be possible to isolate each area by disconnecting them and measuring the -17V voltage. But this is sometimes risky.

    But if you are up to it, it might just be possible.

    If the fault is located at the big PCB's you will need a hot gun (for the SMD's)
     
  9. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    So you finally bought it (without the seller fixing it)or did you offer $100
     
  10. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    It is an all linear regulator, so it should regulate ok with no load, a good starting point. Disconnect the ps from the rest of the board and measure all three outputs. If all are present, then...

    This mixer is multiple identical subsections bussed together, so the odds are that most of it is ok and one section has a bad part. If everything really is tied together with ribbon cable as it looks, isolate the sections so only one at a time has power, and record the ps outputs. With a little luck, this will narrow the problem down to one section board, with all other sections able to run when connected together to the ps.

    Please give us a photo of the top of the console so we can see what the sections do.

    ak
     
  11. ian field

    Distinguished Member

    Oct 27, 2012
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    Looks like several boards with connectors - may be possible to re-introduce one board at a time and see which one knocks out the PSU.
     
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