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Vox AC30 / 6 TB ,all valve combo from 2002

Discussion in 'Electronic Repair' started by N Cook, Oct 29, 2007.

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  1. N Cook

    N Cook Guest

    Ideally identifying which and dismissing the roady would make more sense for
    this locally based, but made big-time band.
    Failing that - concerning cut grommets encircling valves to act as retainers
    in inverted amps. Lining the holes in the chassis where the valves pass
    through .
    a/ fairly rigid rubber of otherwise standard trunking grommets
    b/ fairly tight to the glass envelopes to function as retainers.
    c/ obviously they do no take much a jarr to cause breakage as no obvious
    damage to the cab.

    The 4 o/p valves have spring retainers.
    One of the ECC83 quite neatly split in a ring where the grommet lies and
    white cap.
    I am thinking of running my plaited, high temperature silicone cord "rope",
    over the tops of all 6 of these small valves , located over the top "pips"
    and anchored to the chasis at the ends.
    Any comments pro or con ?
     
  2. Ron(UK)

    Ron(UK) Guest

    Don't the ecc83`s have screening cans on them? that`s the usual method
    of keeping them in their sockets and protecting them.


    Ron(UK)
     
  3. N Cook

    N Cook Guest


    No skirts around the bases on the pcb or on the chassis so screening cans
    were never used on this model.
    It would be quite a work up to introduce cans on this.
    The chassis holes are about 3/4 inch above the valve bases, perhaps that
    gives a certain amount of screening
     
  4. Ron(UK)

    Ron(UK) Guest

    Do the bases have those little 'pips' to clip a retaining spring into?

    Maybe a decent flight case is the answer, and a more careful roadie!

    Ron
     
  5. Tim Shoppa

    Tim Shoppa Guest

    I think the problem is not retention of the miniature tubes, but the
    fact that their socket (some distance under the chassis) obviously was
    jarred and shifted/vibrated enough to cause the tube envelope to hit
    the chassis hole.

    I think that enlarging the hole or stiffening the chassis is your only
    choice. Retainers keep tubes in their sockets, but do not stop the
    socket from moving under the hole.

    Tim.
     
  6. Marra

    Marra Guest

    The old valve TV's used to have a wire clip over the top of the valce
    to stop them falling out.
     
  7. boardjunkie

    boardjunkie Guest

    I had an AC30CC in recently. I don't like how they did that grommet
    thing on the preamp tubes. They really don't do *anything* besides
    provide damping to the glass envelope. What I would do is enlarge the
    chassis holes and put in larger grommets. Make sure the tube can be
    worked out of the socket with the grommet in place...don't go too
    small. Then the idea of strapping them down with some sort of retainer
    isn't a bad idea as long as yer in there.
     
  8. N Cook

    N Cook Guest

    I can really only probe through the chasis holes but the bases seem smooth
    sided.
    I won't be desoldering wires etc to remove the pcb when all else is fine.
    I've made a mounts to one bolt for each transformer , remove all 6
    grommets and tie down the valves using the glass-melt-draw pips on the valve
    tops.
    I usually use this plaited silicone cord or sleeving to stop a line of
    emiter resistors (well split into 2 so there is a joint to anchor to) from
    vibrating in combo amps .
     
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