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Loud "boom!" When Powering up Kawai SR7A

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  • Loud "boom!" When Powering up Kawai SR7A

    Our church has a Kawai SR7A electronic organ. We've had it since the late '80's and have had NO problems with it...except for one annoying thing. When you power up the organ, it makes a loud "boom". It's noticeable through the internal speakers, but it's VERY loud through the church's PA system. The way we deal with it is to make sure the mixer channel for the organ is muted until the organist has powered-up, and then turn it on through the system. But, of course, sometimes we forget and the people in the church all jump when she hits the power button and the "Boom!" comes through the system.
    We use the line-out jacks near the bottom of the rear of the organ. The organ sounds fantastic in all other respects.
    Does anyone have any ideas as to how to muffle the initial start-up on this organ?
    Brett Barnes
    Roopville Road Baptist Church
    Roopville, GA

  • #2

    Sounds like there is no muting on the pre-amp or power amp, so you get a loud bang on turn-on. Possibly there is a faulty muting circuit. Maybe it would be wise to put a switch on the audio outputs, so the audio gets switched separately from the power supplies.

    Be careful if you get big bangs. This can damage circuitry, amps, or speakers.

    And this is no BIG BANG THEORY.



    • #3
      *** Please post your questions about technical service or repair matters ON THE FORUM. Do not send your questions to me or another member by private message. Information shared is for the benefit of the entire organ community, but other folks will not be helped by information we exchange in private messages!


      • #4
        I'm told the sound is created in the amp due to the voltage levels rising unevenly, a common situation. We had a problem with our Devtronix amp doing the same thing. They sent us a board with relays on it. It's been a lot of years, but I seem to remember that the board was basically a time delay that energized the relays a few seconds after power up. The relays, I believe, were between the amps and speakers, so that the amps were settled down before they were connected to the speakers. It worked well for years, and as far as I know, is still in place. The board also stopped the noise created when powering off, as the relays dropped out instantly, and the amps died quietly, not being connected to the speakers.
        Home organ, same as church's organ - Rodgers 940

        Sign on my work toolbox that effectively keeps people away:

        DANGER!!! 1,000,000 OHMS!!!