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Casio keyboard has really low volume

Discussion in 'Troubleshooting and Repair' started by Rick79, Apr 11, 2016.

  1. Rick79

    Rick79

    268
    3
    Nov 26, 2014
    I found a Casio CTK-720 in the trash. It looks in good condition, but it has an abnormally low volume through speakers and headphones. I opened it up and I don't see any damage on the circuit board anywhere. Is this a sign of a failed component or possibly something else I cant see? It doesn't look like it got wet or dropped. Could a power overload cause this?
    I tried new batteries and the correct voltage AC adapter.
     
  2. shrtrnd

    shrtrnd

    3,670
    453
    Jan 15, 2010
    It sounds like a bad component, but I'd check the speaker/headphone jack itself first. Make sure some leaf contact isn't bent out of shape.
    Odds are that the output amplifier transistors took a hit. Maybe from excessive output, maybe from using a wrong-impedance output load.
    Did you look on-line for a schematic of your unit?
     
  3. Rick79

    Rick79

    268
    3
    Nov 26, 2014
    Thanks for the reply. OK, I'll check out that headphones Jack. And no I haven't looked up the schematic yet. I guess I should have posted some photos.
    Would the transistors look burnt?
     
  4. davenn

    davenn Moderator

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    Sep 5, 2009
    not likely ... they can easily fail without any visible signs externally
     
    Rick79 likes this.
  5. Rick79

    Rick79

    268
    3
    Nov 26, 2014
     

    Attached Files:

  6. Rick79

    Rick79

    268
    3
    Nov 26, 2014
    I checked the Jack and I didn't see anything wrong. Can you tell what component is the output amplifier transistor?
     
  7. davenn

    davenn Moderator

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    Sep 5, 2009
    It's that LA4227 IC
     
  8. Rick79

    Rick79

    268
    3
    Nov 26, 2014
    Thanks! Are those available at electronics parts stores?
     
  9. davenn

    davenn Moderator

    13,294
    1,758
    Sep 5, 2009
    you would probably need to go to one of the big suppliers, RS, Digikey, mouser etc
     
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