BL8000 starts in green and hum

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  • #6733
    Pindsen
    BRONZE Member
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    I am looking at an Beolab 8000 which puzzle me.

    There are no audio cable connected, when AC power is turned on it starts with green LED and hum – I would expect red LED and no hum.
    There are GND connection from audio connector to PCB2 connector P4-3.
    Apprently is picks up noise internally, but where from?
    Any idea what that could be?

    /Pindsen

    #6737
    KolfMAKER
    BRONZE Member
    • The Netherlands
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    Did you connect a Powerlink or RCA cable to one of the connectors?

    what do you see and hear when you do that?

    #6748
    Pindsen
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    No I tried without any audio cable because that to me should be a good starting point where I would expect red LED and total silence.

    If I apply a powerlink cable it is more or less the same with green LED and around same hum, but if I apply an RCA cable the hum gets a lot higher.

    #6772
    Pindsen
    BRONZE Member
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    I have discovered that if the outer aluminium part is being touched it increases the hum. My assumption is that the aluminium part is/or should be “grounded” to the amplifier via the six screws?

    Another discovery is that when doing a short circuit of the RCA input the noise in the RCA switch selection lowers to nearly nothing.

    I have tried to see if the internal cabling is correct, and it seems like. It though wonders me why the audio cable runs directly under the transformer.

    #6795
    Pindsen
    BRONZE Member
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    Okay, to finish up my own thread 🙂 my conclusion is now that there did not exist a proper connection between aluminium part and amplifier despite being screwed together. I noticed that the screws are some kind of black CED coated, and by working the screws back and forth several times the hum disappeared and the speaker now works as it should.

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