Refurbish treble panel

<under construction>

For sure, procedure is rather close to refurbishing bass panel. Just more complex.

Tip: do not repair what is not broken

This one needs to be repaired !:

What you hear: http://esl.drakkapps.com/wp-content/uploads/2020/01/IMG_5585.mov

What you see: http://esl.drakkapps.com/wp-content/uploads/2020/01/IMG_5586.mov

Some measurements

Just a sanity check. With one probe on long red wire (polarisation of diaphragm), resistance from this wire to all other ones will be > 500MOhm (no leakage), whereas capacitance will be approximately 180pF with blue wires (medium) and 150pF with brown wires (center, treble). If you cell has arced, you will not get this information from this basic check.

Arcing made his hole in this treble cell

Dust covers

Same procedure as for dust cover for bass panels. A reparation is sometimes possible when wrinkles are visible. See below, using a heat gun set at 100°C.

Old dust covers. Wrinkles are to be avoided
Wrinkles removed using a heat gun

Open cell

Use a plier to squeeze the head of the rivet in one direction then in the other. Cut the head (wear glasses !) then push gently and remove the other part of the rivet from the other side. Plan for 45min to remove 56 rivets (vs about 66 for bass cells).

Note for refurbishers: treble cells are 4.4mm thick, rivets have a diameter of 3.2mm. M3x6 screws and low profile nuts (1.8mm) are adequate as replacement: this is what I use. If rivets are preferred: 4.4*1.1+3.2*1.5=9.64 : 3.2x10mm can be tried. For bass cells: M3x10 / 3.2×14.

The head of the rivet being cut (from the other side) it can now be removed

Tip: do not remove the 2*2 rivets that are used to power the diaphragm (red wire)

Treble cell opened. This one is still good for use
New wires and nuts&screws to replace rivets

Tip: use low profile bolts to avoid changing overall thickness of the cell

New wires: long enough to be confortable to solder the audio input transformer:

  • 44 cm for the 2 blue ones
  • 35 cm for the 2 brown ones
  • 64 cm for the red one

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