DSR-1000 (1987) Audio Problem / Static background noise is much too loud

Discussion in 'Yamaha Keyboards' started by Streets, Jul 11, 2018 at 7:33 PM.

  1. Streets

    Streets

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    Hello!

    I´ve just bought a vintage Yamaha DSR-1000 Keyboard.
    It´s overall in good shape, but has one significant problem.

    There´s a static/white noise comming form all Audio-Outputs while the Keyboard is on. The Sounds/Synth/Rythm ect. works.
    This static noise is much too loud. It is the same noise you can hear from any speakers with volume at max.
    But here you can hear it very loud, even the Master Volume is at 50%.
    It comes to all Audio Outs: AUX-Out, Headphones and even the build in speakers.
    I know, a bit of noise is alwasy normal, but not on that loud.

    The DSR-1000 has several Volume Controls.
    One for the Master Volume and additional ones for Synth-Volume and Rythm Volume.
    If you turn the Master Volume up or down, so does the volume of the noise.
    But if you turn the other Volume Controls for Synth oder Rythm, the noise does not chance.

    And there is one more thing. If you wait about 10-20 seconds, you can hear a short "PLOP" comming throu the audio-out.
    Then, the noise is gone...until you hit a key to play a tone. The noise comes back.
    Then you can wait again for 10-20 seconds....ect.

    Does anyone ever heard of such a thing?

    I heard about many things that might cause this problem:
    - Old or bad capacitors
    - Bad OP-AMP Chips
    - Bad DAC Chips
    - Bad Reverb Chip
    and so on.

    By the way. It is not the Power-Supply unit. I´ve testet 2 of them. Both are OK and working (with other Keyboards,too)
     
    Streets, Jul 11, 2018 at 7:33 PM
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  2. Streets

    happyrat1 Destroyer of Eardrums!!!

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    Most likely it is old leaky electrolytic capacitors and noisy pot controls.

    The pots can be fixed by cleaning them.

    The caps pretty much have to be replaced.

    Gary ;)
     
    happyrat1, Jul 11, 2018 at 9:00 PM
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  3. Streets

    Streets

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    I´ve done a complete recap. No change :(
    Cleaned the pots, too .
     
    Streets, Jul 12, 2018 at 1:12 PM
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  4. Streets

    happyrat1 Destroyer of Eardrums!!!

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    Only other thing I can think of is using a scope to trace the signal path to hopefully find a cold or cracked solder joint or a defective semiconductor.

    Gary ;)
     
    happyrat1, Jul 12, 2018 at 1:23 PM
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  5. Streets

    happyrat1 Destroyer of Eardrums!!!

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    happyrat1, Jul 12, 2018 at 1:30 PM
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  6. Streets

    Streets

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    Thanks.


    I´ve resolderd all joints with no success.
    Then It must be an IC. (There is nothing more left to change ;)
    Maybe the OpAmps. 4558DVs.
    I´ll change them to 4558Ds. I wonder if can use 4559Ds as well. o_O
     
    Streets, Jul 13, 2018 at 9:01 PM
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  7. Streets

    happyrat1 Destroyer of Eardrums!!!

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    Before you start randomly desoldering and replacing ICs I'd do a signal trace and see if I could locate the faulty chip.

    Like you said, it could be a faulty DSP as well.

    Gary ;)
     
    happyrat1, Jul 13, 2018 at 10:09 PM
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  8. Streets

    Streets

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    I found out somthing more!
    Beside the noise, I thought the sound was overall very dull,...no trebble..flat....
    So I pluged in the Yamaha PSR90, with the exact FM Chip, the OPZ.
    The Instrument Sound ist the same, but the PSR-90 is much more brighter, bigger in Sound.
    I think the frequence spectrum on the DSR-1000 is cutted, too.

    I don´t know how to locate a bad chip with my multimeter ;)
    But I know someone who can. And then I hope I will finally learn this (for the next time)
     
    Streets, Jul 14, 2018 at 2:31 PM
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  9. Streets

    happyrat1 Destroyer of Eardrums!!!

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    Like I said earlier. Buy a $50 pocket oscilloscope and track the noise in circuit.

    There's no way in hell you're going to track a noisy chip with a DVOM.

    Simply not doable.

    Gary ;)
     
    happyrat1, Jul 14, 2018 at 8:43 PM
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  10. Streets

    happyrat1 Destroyer of Eardrums!!!

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    1 usarmy troubleshooting chart.jpg

    :D :D :D

    Gary ;)
     
    happyrat1, Jul 15, 2018 at 3:36 PM
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