Repairing Dapol Motorized Signals
I recently bought some Dapol signals. They were the lower quadrant type. One of them got zapped when the power source was accidentally short circuited. The symptoms were over heating of the unit and the signal not changing.
After removing the cover which is held by a small Philip head screw, I noticed that one of the components was hot. The power was disconnected. Further examination revealed that the motor appeared to be ceased. The blue wire to it was UN-soldered. A five volt DC supply voltage was momentarily applied in each direction. The first attempt failed but on the second attempt the motor fired up. After giving it a bit of a run I soldered it back into the circuit.
To put these signals back together it is necessary to hold the signal in the proceed position to avoid fouling the drive mechanism on the actuation arm. Care must be taken to make sure that the worm gear is in the right position and the switching mechanism is between the two limit switches. Also care must be taken not to squash any of the wires in the plastic moldings during reassembly. The accompanying picture shows what to look out for. The red arrows show the parts that foul while trying to assemble. The green arrow shows where I unsoldered the blue wire. The green arrow shows the worm drive disconnected. The worm drive must be connected to the motor and the switching mechanism needs to be engauged in the worm drive. The motor assembly is held above the circuit board section and the end near the signal base inserted first. It needs to be fully up against the signal base before lowering the rear end. 
I think the motor’s rotor some how annealed and stopped it from turning. Hope this helps someone. Some times it is not necessary to wreck down a signal when it doesn’t work. I have seen some to these signals wrecked down and operated with points motors. Not quite the manufactures intentions and not as satisfying as the original signal.