I rescued this pair of Scott 166 from a family member who was getting rid of them. These are a sealed 6 1/2" 2-way bookshelf design from the late 70s I believe. Construction appears to be decent with a heavy cabinet, foam filling, an actual crossover network, and a good-sized woofer magnet with a vented pole piece. The cabinets, grills, spiders and surrounds are all in excellent condition visually. Both speakers were playing at low volume briefly when the woofer stopped working on one side; the working speaker actually sounds pretty good. I should have some time between Christmas and New Years and would like to attempt a repair.
Initial investigation revealed that the dead woofer was open-circuit. Since then I have lifted the dustcap, and scraped back the black VC lead glue to find where the break is. It turned out that the VC itself still has continuity (measured 5.9R) and the open circuit is somewhere in the lead between the VC and where it passes under the dustcap and exits the cone.
Questions for the knowledgeable folks here:
Initial investigation revealed that the dead woofer was open-circuit. Since then I have lifted the dustcap, and scraped back the black VC lead glue to find where the break is. It turned out that the VC itself still has continuity (measured 5.9R) and the open circuit is somewhere in the lead between the VC and where it passes under the dustcap and exits the cone.
Questions for the knowledgeable folks here:
- What solvents can be used on the hard black glue over the VC lead wires? I have acetone on hand, or could pick up some of the box store "lacquer thinner" (per SDS mostly toluene, with xylene, methanol, acetone, and MEK).
- What are the correct adhesive(s) to (i) cover the VC lead wires post repair, and (ii) reattach the dust cap?
- Any pro tips on soldering in very close proximity to a paper cone?
Using a sharp blade (x-acto type knife) scrape off some of that black stuff to expose some of the voice coil wire next to the break.
Next gently scrape the enamel off that section of voice coil wire.
This should expose enough copper for you to solder a suitably sized strand of copper wire across the break.
EDIT: That may not be where the break is, if I read you correctly - see below.
Next gently scrape the enamel off that section of voice coil wire.
This should expose enough copper for you to solder a suitably sized strand of copper wire across the break.
EDIT: That may not be where the break is, if I read you correctly - see below.
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In that case, you may have to unwind one turn of the voice coil wire to gain enough length to make the repair.
As far as solvents, the acetone should do it. Easy enough to get a little on a Q-Tip and swirl around on the goop and see if it picks up some black color. If it does, it's dissolving it. In my experience, methyl ethyl ketone is the most potent available solvent. It's kind of nasty--have good ventilation--but will even dissolve things like cured urethane varnish.
If the lead-coating varnish is not flexible, something as basic as nail polish or hobby-store lacquer/enamel should be fine. If it needs to be flexible, there are some solvent-based (non-curing) adhesives like "Goop" available that should work if they're liquid enough.
If you get the leads detached from the paper to fix them, solder with them up off the paper surface. You might slip a couple of layers of aluminum foil underneath if you worry about the soldering iron wandering.
If the lead-coating varnish is not flexible, something as basic as nail polish or hobby-store lacquer/enamel should be fine. If it needs to be flexible, there are some solvent-based (non-curing) adhesives like "Goop" available that should work if they're liquid enough.
If you get the leads detached from the paper to fix them, solder with them up off the paper surface. You might slip a couple of layers of aluminum foil underneath if you worry about the soldering iron wandering.
Thanks.. yeah the black glue covering the lead wires is rock hard. I'll give the acetone a try first then.
Well, that was ... anticlimactic --
Acetone softened the black glue enough to dig away and eventually daylight the wire underneath using a scalpel... and although the wire was somewhat green and corroded, it was intact. Re-checking the terminals with the multimeter, lo and behold continuity was restored. Not sure what happened here, but I'll take it. Trench filled and dustcap reattached with some clear-drying wood glue, and these are back to making music. 😀
Acetone softened the black glue enough to dig away and eventually daylight the wire underneath using a scalpel... and although the wire was somewhat green and corroded, it was intact. Re-checking the terminals with the multimeter, lo and behold continuity was restored. Not sure what happened here, but I'll take it. Trench filled and dustcap reattached with some clear-drying wood glue, and these are back to making music. 😀
