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Vox AC30CC2x

Discussion in 'Electronic Repair' started by N_Cook, Oct 27, 2009.

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  1. N_Cook

    N_Cook Guest

    Once again roadies throwing things around. Previously they managed to shear
    an ECC83 in half, where they pass through the chassis "protected" by rubber
    grommet. Thius time broken springline and choke bent over, by G-force, so
    nearly touching the rectifier valve. Anyway the main problem was
    intermittent squeel on the output with all controls at minimum.
    Squeel would occur with first 2 preamp valves removed and also the
    splitter/driver valve removed. I expected to find serious CH/R problem on an
    EL84. Anyway all output and preamp (and rectifier ) valves test absolutely
    fine on gain and CH/R over my FSD of 30 Megohm.
    Replacing everything, the squeel has gone, trying the amp upside down also.
    Earthing, Cs and Rs and Vs seem fine and no squeel emerges with serious
    twizzle-sticking.
    Assuming not a valve problem and something wrong in valvebase/ wiring /
    soldering what/ where to look for something amiss that could cause a squeel
    ? Of course, not wanting to replace 4 x EL84 if there is a lurking problem.
    I cant even swap pairs as the problem has "gone" Looks as though I'll have
    to desolder the pa pcb to have a look underneath. While doing that does
    anyone replace with slightly longer wires? or is that likely to introduce
    oscillation problems as well.
     
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