Reproducers

Columbia Floating Reproducer Restoration

Posted on by John Nagy

Here is the process for fitting your repair parts into the Columbia large floating aluminum reproducer, like the one shown here. The internal diameter (diaphragm size) is 1-3/4 inches (~4.5 cm). This process also applies to the smaller Columbia aluminum floating reproducers.

What You Will Need

  • Bunsen burner
  • Denatured alcohol
  • Matches
  • Round toothpicks
  • Small, fresh tube of super glue
  • Quick-setting epoxy
  • Thick metal washer – see (6) below
  • Many pieces of approximately 3″x3″ paper towels
  • Fresh stick of clear bees wax
  • Clean surface
  • Small bowl to keep small pieces from getting lost

The (1) diaphragm center has to be drilled with a carbide micro-miniature drill size 1.55mm (0.061″) being careful to avoid fraying the center hole. This will allow the (2) stylus hub to be installed, the back first getting the tiny washer, then the tiny hex nut. These are tightly screwed to the back end of the hub. A droplet of super glue is placed on the hex nut to avoid future loosening.

Next, test to see how the (2) stylus fits in the hub opening. The round part of the stylus should stick out of the opening about 1/16″ or ~2 mm. If the stylus is totally contained in the hub hole, remove the stylus and insert into the hub hole a tiny piece (~1 mm) of the toothpick to make sure the stylus will stick out of the hub hole after it is glued in there.

If satisfied, then a small amount of quick setting epoxy is prepared, stirred with a round toothpick end, and a droplet of the epoxy is pushed into the hub opening where the stylus will be inserted. (There isn’t much time to do this process because the epoxy dries and sets rapidly.) The (2) stylus is coated with the epoxy mixture and slowly inserted into the hub hole with the round part of the stylus sticking out about 1/16″ or ~2 mm. Excess epoxy is wiped off with a finger exposing only the round part of the stylus. The stylus should be centered in the hub. Set the diaphragm aside for a while to allow the stylus to be firmly set in the hub hole. Wait for the epoxy to dry.

After cleaning the “inside,” the (3) reproducer is heated (not hot) using a denatured alcohol flame; then (4) the wax-impregnated white paper gasket is inserted.  (5) The readied diaphragm is inserted over the gasket; (6) a thick metal washer (smaller than the diaphragm, with a hole much larger than the hub) is placed over the diaphragm. The weight of the washer will squeeze the diaphragm over the gasket. More heat (just a bit) may be applied under the reproducer to soften the waxy gasket and produce a nice seal when the metal washer presses the diaphragm against the waxy gasket. Remove the heat, keep the washer on the diaphragm, and allow the reproducer to cool only a bit (but still a bit warm), then carefully remove the metal washer.

Lastly, sealing the outside of the diaphragm with bees wax: have in hand a stick of bees wax and a lit Bunsen burner using denatured alcohol for a small flame. Holding the reproducer with the diaphragm side “up” in one hand, and the bees wax stick in the other hand, very briefly hold the end of the bees wax over the flame to soften a bit of the wax. Quickly rub the softened bees wax over the edge of the reproduce allowing less than a drop to settle over the diaphragm. (A bit more heat under the reproducer is needed occasionally to keep the reproducer warm but not hot.) After each drop, with a fingernail, press the softened wax against the inside edge of the reproducer. Keep doing this until the entire inside edge of the reproducer is filled with the softened wax. The wax should be a bit soft but not melted. With the fingernail, spread the wax evenly all the way around, removing excess as necessary, keeping the wax firmly pressed into the edge. A cross-section of the wax should approximately resemble a 45-45-90 degree triangle. (Too much wax will impede the music volume, and not enough wax may loosen the diaphragm seal.) Extinguish the flame!

Clean off wax residue from the diaphragm by wiping off the wax from the center outward with bits of clean paper towels. The end result should look close to what you see in these pictures.

Pat yourself on the back for a job well done.