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Hum problem on a valve amp

Discussion in 'Electronic Repair' started by N Cook, Dec 23, 2006.

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  1. N Cook

    N Cook Guest

    Actually a Velleman K4000 kit stereo valve amp from 1994.
    Not just hum but mains noise, eg dimmer spike noise.
    It would seem to not have a proper grounding point.
    Specially thickened ground lines on the ps board, large ground interconnects
    to the preamp and main amp 0V lines and input sockets insulated isolated
    from chassis which is bonded to the 3 wire mains input at the IEC socket.
    The kit construction literature makes no reference to connecting the
    thickened ps ground lines to the mains bond point and seemingly relying on
    earthing of whatever is used as a non-integrated preamp or external source.
    What is the point of reinforced ps ground tracks if they conduct current
    nowhere , only via signal line braid, so a safety issue as well
    Surely there should be a heavy strap between the ps ground and the mains
    ground point ? I only have the amp for attention which is line level input
    to speaker output so no volume or tone controls.
     
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