BeoLab 8000: high frequency noise disturbs switching to OFF

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Home Forums Product Discussion & Questions BeoLab BeoLab 8000: high frequency noise disturbs switching to OFF

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  • #48882
    KolfMAKER
    BRONZE Member
      • The Netherlands
      • Topics Started 28
      • Total Posts 228

      Update

      • On > Off> On > … – When first powering up the BeoLab 8000, the auto stand-by switch works normal and switches from On to Off/stand-by after music stopped. But after some 15 minutes or so, the auto stand-by does not work normal anymore, and switches back and forth between On and Off. (Something to do with warming up?)
      • High frequency noise – I found after thoroughly cleaning the track side of PCB01/02, that the high frequency seemed to have gone. But I know noticed that sometimes it is there and then it is gone for a while and returns again.
      • Hum – The hum increase when touching the casing or AMP/PSU panel is still there
      #48881
      KolfMAKER
      BRONZE Member
        • The Netherlands
        • Topics Started 28
        • Total Posts 228

        I have an issue with one BeoLab 8000, serial# 1086xxxx

        My use: I play music via the RCA input plug in the foot. (So no PowerLink use)

        My issue: The BeoLab does not switch back to stand-by/Off. Instead, it switches repeatedly to Off > On > Off, …

        What I noticed (both when listening close to the speaker drivers, at 1 meter distance these two matters can not be heard).

        • When I play no music and keep my ear close to the speaker drivers, I can hear high frequency noise (especially at the tweeter of course).
        • When I touch the casing or the AMP/PSU metal panel, there is a slight hum increase.

        What I have done

        • Since this is a speaker with old foam, I had to clean the foam rot. So I have meticulously cleaned all PCB’s (incl PCB05 and 06), components and connectors.
        • I have checked for broken solder joints or PCB traces (incl. measuring continuity). Couldn’t find them but re-flowed solder joints on PCB 01/02 just to be sure.
        • Measured voltage output of Trafo T2: 2x 20 volts DC.

         

        Questions

        • What could be wrong?
        • What should I do next?
        #48883
        espresso_fanatic
        BRONZE Member
          • Topics Started 1
          • Total Posts 3

          I wish I had a solution here. I have a pair of BeoLab 8000’s as well and one of them exhibits the same issue. It toggles very quickly and has some high frequency noise like you mentioned. I am in the process of repairing the amplifier in hope of finding where the noise is coming from.

          #48884
          KolfMAKER
          BRONZE Member
            • The Netherlands
            • Topics Started 28
            • Total Posts 228

            Update 2

            Someone gave me the tip to reflow all solder joints on PCB05:

            PCB05 - Top view Close-up

            So I did. Again, the first 10 to 15 minutes, the auto stand-by switching worked well. But suddenly after that time, the repeatedly Off > On > Off > On switching started again. So still no resolution found.

            Tips are welcome.

            #48885
            espresso_fanatic
            BRONZE Member
              • Topics Started 1
              • Total Posts 3

              I recently redid the entire board and found some possibly helpful notes:
              – Check C6, 22 uf. When this capacitor gets drained, it seems to switch the speaker into standby mode. This might be bad given its age.
              – IC1 could have gone bad but I suspect the capacitor more than IC1. Desoldering SMD components is quite trick as well.

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