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Yamaha YPG-635 Keyboard with No Sound

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    Yamaha YPG-635 Keyboard with No Sound

    I have a Yamaha YPG-635 that will not make any sound either thru the headphones or the speakers, I'm thinking that the amplifier/power PCB is no good. I've tried to go thru and reset all the menu settings as well. Does anyone have recommendations on what I can troubleshoot on the board?

    Also, if there is a better place to post this related to circuit repair please let me know. Thanks!

    Here are a few photos of the board. I can pull it and get a photo of the traces tomorrow.
    https://imgur.com/V7neazz
    https://imgur.com/bLLDQ3h

    #2
    Re: Yamaha YPG-635 Keyboard with No Sound

    The first thing to do would be remove the amp board and check for poor solder connections, I have seen this before on other keyboards, If the connections are ok, check the voltage going to the board.

    Also if you can Attach the pictures to the post would be best.
    Last edited by R_J; 02-26-2020, 10:44 AM.

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      #3
      Re: Yamaha YPG-635 Keyboard with No Sound

      Here are some photos and an update,

      I built myself a little signal tracer with a headphone amplifier. And found out I have sound on Pins 1 and 6 of the LA4625. I have 11.75 on Pin 14. What else can I check? I'm assuming as of now that LA4625 is dead?
      Attached Files

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        #4
        Re: Yamaha YPG-635 Keyboard with No Sound

        Here is the board labeled as well.
        Attached Files

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          #5
          Re: Yamaha YPG-635 Keyboard with No Sound

          Check the voltage on pin#4 this is the standby pin and needs to be at +5 volts, It looks like R214 connects pin 14 to pin4 to supply the standby on. Check the voltage on pin 5, (+2.3v) and pin 7 (+2.0v)
          Also check the voltage on the speaker pins, or the output pins of the ic, They should be about +5 voltes each. It could be the ic is bad. It has protection so it could be internally shut down
          Last edited by R_J; 02-26-2020, 10:19 PM.

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            #6
            Re: Yamaha YPG-635 Keyboard with No Sound

            Pin 4 has just below 5 volts, I'm thinking you meant R205 which seems to be correct. Voltage on Pin5 is Present and Pin 7. Voltage is between 4-4.5v on the speaker pins.

            I'm assuming that this means LA 4625 is dead?

            Also the ribbon cable pictured pretty much feel apart, the plastic tabs just feel off, I bent the pins back and superglued it back together but I'm not counting on it surviving me taking it out and replacing it again when I solder the new parts in. How can I find a replacement for this? Can it be cut from a larger pin one? And would I be able to use some Cat5 or something just to solder a jumper, or would this cause issues with noise or interference?
            Attached Files

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              #7
              Re: Yamaha YPG-635 Keyboard with No Sound

              How does Pin 2 work?

              Comment


                #8
                Re: Yamaha YPG-635 Keyboard with No Sound

                Just checking back. Thanks!

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                  #9
                  Re: Yamaha YPG-635 Keyboard with No Sound

                  Originally posted by ComputerGeek View Post
                  How does Pin 2 work?
                  It is just a filter, it smooths the bias voltage.
                  The TWO connectors pictured look ok, What is broken? how did you break them? The cable pulls straight out and pushes straight in. You will need to search the internet for them, search for FPC or FFC connectors, you will need to know the pin pitch (distance between conductors on the flat cable) There is nothing to the circuit, so if you can confirm you have a good audio level on the ic's input, it is likely the ic is bad.
                  Last edited by R_J; 03-02-2020, 11:33 AM.

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                    #10
                    Re: Yamaha YPG-635 Keyboard with No Sound

                    So, unfortunately I got a replacement LA 4625 in yesterday and soldered it in, but no luck on getting it alive, I verified all the pins are connected well and there are no shorts. Any other ideas before I let this one go?

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                      #11
                      Re: Yamaha YPG-635 Keyboard with No Sound

                      Are you sure you have sound on pins 1 & 6 of the ic? Is it of sufficient level? Try connecting a small speaker directly to the amp output (see picture, Red is one spkr Pair, Green is the other skr pair) this will bypass the HP jack etc.
                      Attached Files
                      Last edited by R_J; 04-05-2020, 02:36 PM.

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