Bose PS28 III Subwoofer Power Block need issue diagnosing help

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  • BlueVelvet
    New Member
    • Jul 2019
    • 3
    • United States
    #1

    Bose PS28 III Subwoofer Power Block need issue diagnosing help

    Hello, like to begin with that I'm a complete novice but I've managed to follow certain videos online to help me fix this but I am now stuck.

    The subwoofer is the Bose PS28 III.
    Using this youtube video (https://www.youtube.com/watch?v=s9GarjV3zzs) I have managed to diagnose with a multi-meter that the issue may be coming from the power supply board (PN: 286612-002)

    An older thread on this forum (https://www.badcaps.net/forum/showthread.php?t=65417) helped me find the schematics for the issue (although to be frank, I personally, have no idea what to do with that.)

    I am able to follow the youtube video all the way until the 3:04 mark in the video (when the person starts to diagnose what specific components are shortened/blown in his board). I understand this is going to be different for everyone, however, my issue is that unlike the video (which seems to have very obviously identifiable issues), I am unable to find any blatant issues with the power supply board I'm working with. I'm hoping someone here can look at these pictures I've provided and help me see the obvious.

    Photo album - https://imgur.com/a/0fjIG7v

    Thank you!

    Edit: I've noticed the images didn't upload in full res. I'll update soon with better photos.
    Last edited by BlueVelvet; 07-09-2019, 10:51 AM.
    Tags: None
    • BlueVelvet
      New Member
      • Jul 2019
      • 3
      • United States
      #2
      Re: Bose PS28 III Subwoofer Power Block need issue diagnosing help

      Here are better photos.
      Attached Files

        Comment

        • roberhoz
          New Member
          • Jun 2018
          • 1
          • United States
          #3
          Re: Bose PS28 III Subwoofer Power Block need issue diagnosing help

          Check these components. Inside the circle marked in yellow in the image.
          Attached Files

            Comment

            • momaka
              master hoarder
              • May 2008
              • 12170
              • Bulgaria
              #4
              Re: Bose PS28 III Subwoofer Power Block need issue diagnosing help

              Could you describe what issue(s) you're having with your subwoofer?
              I think that might help us narrow it down where to look.

              The issue in the Youtube video you linked shows a blown amplifier power supply, which was repaired by changing the primary-side MOSFETs, MOSFET drive circuits, and PWM IC.

                Comment

                • stj
                  Great Sage 齊天大聖
                  • Dec 2009
                  • 30997
                  • Albion
                  #5
                  Re: Bose PS28 III Subwoofer Power Block need issue diagnosing help

                  nice design, wouldnt want c117 & c118 getting cold in the wintertime!
                  /sarc

                    Comment

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