Plate 245:  Wiring the point motors through the distribution center, Part 23: electrically testing a solder joint
(This plate added NOV 2003)

The accompanying picture shows an electrical continuity test being performed upon the solder joint that was completed in Plate 244. Running a continuity test on a solder joint is recommended for people who are not yet confident of their ability to create good solder joints. People with soldering experience can usually appraise a solder joint by visual inspection; they generally do not need to go through this procedure. When we run a continuity test on a solder joint, what we are actually doing is determining whether the solder in the joint is making good electrical contact with the wires that are covered with the solder. We want to be sure the solder is making solid, total, uniform contact with the wires. If this is not the case, the solder joint is "cold", and is in danger of failing at a later time. --more--

In the accompanying picture, the black lead of the continuity tester is clipped to the black "common" wire at the point where the wire is factory-joined to the two solenoids in the point motor. The red lead of the tester is clipped to our solder joint. If our solder joint is "cold" (that is, if it exhibits a high electrical resistance), the continuity tester will indicate a value greater than zero ohms on the meter scale (the zero point is at the right of the meter scale; see Plate 239). To be sure we are running a complete test, we should "jiggle" the joined wires; if the solder is not making solid contact with the wires, the needle in the meter will deflect to the left, indicating intermittent resistance. In our test, the meter solidly indicated "zero ohms" no matter how much we "jiggled" the wires, which means that we created a good solder joint. Go to top of page