Read this for a primer on hand soldering:
technologyinterface.nmsu.edu/fall97/electronics/solder.html
Repairing Motorcycle Soldered Connections on the older bikes.
When repairing soldered wires on motorcycle switches or light bulbs sockets, have the following on hand:
1. A 25 Watt soldering iron or one that the wattage can be adjusted.
2. Rosin core solder of 60/40 type. SN60 or SN63 is preferred.
3. Rosin flux or soldering paste (Never use solder or soldering paste designed for plumbing work, as it contains an acid that will corrode the electrical joint, ruining it).
4. 91% rubbing Alcohol, or 70%. The lower percentage will clean up flux residue, but not as good as the higher percentage stuff. Acetone does a good job of removing excess solder flux too.
5. A cut down ½” paint brush, or acid brush for scrubbing the repaired solder joint.
6. Clean rags or paper towels
7. A damp sponge to keep the soldering iron tip clean.
8. Some “Solder Wick” a braided bare copper wire designed to collect heated excess solder, aiding in joint preperation, available at electronic supply stores.
9. Some wooden toothpicks.
10. Small Hemostats or clip on heatsinks.
A. Before soldering, “Tin” the soldering iron tip by plugging it in or turning the iron on, allowing it to get to operating temperature(2-3 minutes).
B. Unroll about 3” of solder from the roll of rosin core solder & then using a clean rag or paper towel moistened with Alcohol, wipe the unrolled solder, removing the finger print oils that will create a poor solder joint.
C. Apply a small amount of solder to the now heated soldering iron tip, wiping the excess off with the wet sponge, keeping a thin layer on the soldering iron.
D. The soldering iron is now ready for use, but before applying the heated tip to a wire, wipe the tip on the damp sponge, this removes any oxidized solder and makes for a much better connection.
E. If the joint to be repaired is grey in color or appears “Crumbled”, apply some rosin soldering paste or flux to the joint with a small toothpick or screwdriver, and then apply the soldering iron tip for a few seconds.
G. The fluxed joint should clean up, allowing for a better connection. If no luck, use the solder wick to remove all traces of the old solder by apply in it between the soldering iron tip and the bad joint.
H. Hemostats and clip on heatsinks will be used to prevent the wire insulation from burning, overheating & pulling away from the connection.
I. Apply a small amount of flux to the joint to be repaired & then a very short duration of heated soldering iron tip & solder(like a few seconds or so).
J. Clean off the repaired joint with the brush & rubbing Alcohol or Acetone, the newly repaired joint should appear clean and bright, almost as if it were polished, with no voids or holes.
K. When repairing the bad or "Cold Solder Joints" (as the Electronics industry calls them), it takes really no special skills, just patience, and a place to work(along with the mentioned tools. You've got to be sober, and not stoned, as the soldering tool can be at 700 F, possibly giving the impaired bike owner severe burns.
L. If you have fine muscle control problems, have a friend do the soldering for you. Moving a wire before the electrical joint has properly set up, can create "Cold Joints" too. If possible, practice on the bench top with some scrap wires before attempting repairs on the bike.
M. This information comes from years of missile test cable and equipment assembly, when I worked at General Dynamics/Convair Division in San Diego California, on the BGM-109 Tomahawk and later on the AGM-129 Advanced Cruise Missile. This was from 1983-1993. The company had a week long soldering school, where you learned to solder meeting “Mil-Spec” standards.
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