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Thread: Yet another buggy Ensoniq keyboard .. SQ80 - low output

  1. #1
    Junior Member
    Join Date
    Feb 2017

    Yet another buggy Ensoniq keyboard .. SQ80 - low output

    took in a sick SQ80 from a friend
    love hate relationship with these damn things

    screen turns on fine, sends midi signal, so the brain seems to be doing fine

    but it has very low output and the data slider doesn't work
    (can be just barely heard if i run it into an amp and blast the volume)

    so after running through the buchty service manual, tested all the power supply terminals, no fuses blown, cleaned display board connectors

    I guessed it was the sliders

    so I ordered new slider potentiometers from syntaur, replaced those

    NO GO

    any idea where to look next?

    the display board ribbon connectors maybe? they look in good condition to me..

    really seems like it's just the sliders that aren't reporting properly, for whatever reason

  2. #2
    Lifetime Member Enzo's Avatar
    Join Date
    May 2006
    Lansing, Michigan, USA
    So look at the sliders. Is ther 5v across the data slider? Audio across the volume? (Assuming my recall is OK) Does sliding eth data slider cause an even sweep of voltage at the wiper? Does volume slider actually work in circuit? Just because you replaced a slider doesn;t mean the circuit it is in functions.
    Education is what you're left with after you have forgotten what you have learned.

  3. #3
    Junior Member
    Join Date
    Feb 2017
    finally getting back to this

    thanks for your reply Enzo

    I've looked over this a bit more, decided to check the voltage and current coming from the display board into the main board via the J4 connection. At the connection, the voltage and current are varying when I slide the sliders up and down.

    So I am now going through and attempting to read the schematics and test across the main board?

    this is not easy, i'm a beginner by all accounts

  4. #4
    Junior Member
    Join Date
    Feb 2017
    when i said current in that last post i meant resistance

    voltage and resistance at the headphone out remains the same no matter where the volume slider is

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