11-06-2023, 10:20 AM
Before I would tear the speaker down, I would try using a soak in odorless mineral spirits, (odorless has less aromatic solvent). The purpose is to dissolve the wax that has melted from the field coil into the voice coil gap. Mineral spirits will not dissolve the collodion glue that holds the voice coil winding nor loosen the cone to voice coil former bonding. Use an acid brush to flow more mineral spirits
May, want to remove the center spider, first, to do that will need acetone and those long disposable eyedroppers. Use the eyedropper to flow acetone sparingly into the bond of the spider to the voice coil. Repeat maybe several times over 10 minutes, that, should soften the collodion and allow careful removal of the spider. Treasure the spider as no one is making these. Though some have created via 3D printing... Gently flexing the cone while mineral spirit/brush cleaning.
Create shims, three from scrap plastic bottles or cans that can fit between the leaves of the spider. must use three and not very wide, shim equally until it is noticed that the shims are supporting the voice coil and not allowing movement. Place the spider over the shims and down to the apex of the cone. Be sure the hole in the spider is centered over the screw hole in the pole piece. Apply G-C speaker service cement using the eyedropper as a bead around the bond line of the cone/spider. Allow an hour at least for a setup or 6 hours for a hard set, run the screw in the spider and secure to pole piece. Pull shims. Speaker should now be clear of debris and cone centered.
If the procedure fails then knocking apart the speaker is the other option. The frame can be tapped to receive grade 5 screws to re-assemble. The pole piece should be shimmed at the time the magnet yoke is re-installed to keep the pole piece centered.
Grade 5, as one has to really sock down the yoke...
BTW, the wax melted and flowed because of high current load, probably a defective filter cap and/or low bias on PA tube, check...
GL
Chas
May, want to remove the center spider, first, to do that will need acetone and those long disposable eyedroppers. Use the eyedropper to flow acetone sparingly into the bond of the spider to the voice coil. Repeat maybe several times over 10 minutes, that, should soften the collodion and allow careful removal of the spider. Treasure the spider as no one is making these. Though some have created via 3D printing... Gently flexing the cone while mineral spirit/brush cleaning.
Create shims, three from scrap plastic bottles or cans that can fit between the leaves of the spider. must use three and not very wide, shim equally until it is noticed that the shims are supporting the voice coil and not allowing movement. Place the spider over the shims and down to the apex of the cone. Be sure the hole in the spider is centered over the screw hole in the pole piece. Apply G-C speaker service cement using the eyedropper as a bead around the bond line of the cone/spider. Allow an hour at least for a setup or 6 hours for a hard set, run the screw in the spider and secure to pole piece. Pull shims. Speaker should now be clear of debris and cone centered.
If the procedure fails then knocking apart the speaker is the other option. The frame can be tapped to receive grade 5 screws to re-assemble. The pole piece should be shimmed at the time the magnet yoke is re-installed to keep the pole piece centered.
Grade 5, as one has to really sock down the yoke...
BTW, the wax melted and flowed because of high current load, probably a defective filter cap and/or low bias on PA tube, check...
GL
Chas
Pliny the younger
“nihil novum nihil varium nihil quod non semel spectasse sufficiat”
