The over all problem may be non-conductive oxidation or dirt on the wire, trolley pole slider or wheel, track, or wheels. OR, the model no longer runs due to an electrical short circuit.
If you routine for getting the model to operate due to non-conductive oxidation or dirt does not work, STOP trying to pass electrical current through the model!
When the problem is due to an electrical short circuit, the amperage of the power supply can be passing through the entire wiring of the model including the trolley pole.
Resistance in an electrical circuit causes the conversion of the electrical energy into heat energy (heat). The heat can cause problems. Soldered joints in models or wiring will un-solder causing wires to come apart and brass models to deform and come apart. Wire, which is metal in a thin, dawn-out form, will not only deform but will lose other physical properties.
This photo is the power supply installed at 1 end of the test track.
From left to right - a brass rod line side pole with the positive power supply attached with an alligator clip.
At the bottom right is the negative power lead attached to the track.
The black electrical panel part in the center contains the 2 meters.
The black wire coming out of the panel is the positive and negative power leads with alligator clips.
The use of the toggle switch in the bottom center of the panel is unknown.
The toggle switch at the bottom right of the panel controls the direction.
At the right is the small but useful power supply.
Next, the trolley pole was removed (unscrewed) from the model. The pole unscrewed unevenly from the model (This turns out to be an interesting observation.). The positive lead was attached to the 2-56 screw sticking out of the model’s roof. The model still didn’t run.
The part of base which was deformed was a lost wax casting. Small protrusions were filed off. Then the trolley base was placed in a vice to apply enough pressure to straighten the metal casting.
The springs were replaced and the trolley pole moved up and down without any problems. To blacken the part of the trolley pole which had deformed, the lower portion of the trolley pole was dipped into Neolube #2. At the same time this will improved the electrical connection where the 2-56 screw, screws into the trolley base. Allow the Neolube to dry first before attaching the trolley pole to the model.The bottom line of this post is when 1st testing a model which you have never seen run, test it with a power supply having both amp and volt meters. If there is a short, high amperage draw for a comparable model, immediately turn off the power to avoid any damage to the electrical circuit.
Trolley poles are expensive. But at the same time they are the part of the model which sets it apart from other railway models.