Antelope Valley Model Railroad Club
Build an Operating Block Signal Cheaply

This article describes how to build a two-light operating block signal from a non-operating block signal for under $1.50 per unit.

Materials Needed

• 1 Block Signal, Bachmann, #42101 (set of four; one needed)
• 1 LED, green 3mm
• 1 LED, red 3mm
• 9" Wire, black #22 (telephone)
• 9" Wire, green #22 (telephone)
• 9" Wire, red #22 (telephone)
• Glue, super
• Alcohol, denatured
• Paint, black
• Paint, silver
• Putty
• Solder
• Stick, flat wooden stirring
• Tape, masking

• Airbrush (optional)
• Brush, fine
• Cutters, diagonal, small
• File, small flat
• Paper clip
• Pin vise
• Pliers, needle nose
• Sandpaper, 600 grit
• Soldering iron, 25-30 watt
• Twist drill, #70
• Twist drill, 1/16"
• Twist drill, 1/8"
• Twist drill, 5/32"

Procedure

1. Remove any flash from the signal and its ladder.

2. File the numbers on the number board off.

3. File the back of the large collar flat.

4. File the inside bottom 1/8" of the ladder to 1/2 its thickness.

5. Drill a hole in the center of the platform behind the mast with the #70 drill in a pin vise.

6. Drill a hole in the center of the base behind the relay box with the #70 drill in a pin vise.

7. Enlarge the two ladder holes with the 1/16" drill in a pin vise.

8. Enlarge the two lens holes (from the rear) with the 1/8" drill (use your fingers).

9. Enlarge the two lens holes (from the rear) with the 5/32" drill (use your fingers). Drill only 1/32" deep. This is so the base of the LEDs will be flush with the back of the target.

10. Insert the green LED into the lower lens hole from the back. Be sure that the cathode lead (the shorter one) is to the right when looking at the signal from behind. The base of the LED should be flush with the back of the target. Glue LED into place.

11. Insert the red LED into the upper lens hole from the back. Be sure that the cathode lead (the shorter one) is to the right when looking at the signal from behind. The base of the LED should be flush with the back of the target. Glue LED into place.

12. Clip the cathode lead (the shorter one) of the red LED to 1/32". Clip all other leads to 1/2" so that they are easier to work with.

13. Bend the cathode of the lower LED up (at a right angle) so that it makes contact with the cathode lead of the upper LED (use a paper clip next to the cathode of the lower LED so that you will leave enough clearance). Solder the two cathode leads together.

14. Prepare the three 9" lengths of telephone wire by removing 2 1/4" of insulation from one end.

15. Insert the stripped end of the green wire up through the left ladder hole in the base. Make a small hook on the end of the wire then solder it close to the anode of the lower LED.

16. Insert the stripped end of the black wire up through the right ladder hole in the base. Make a small hook on the wire then solder it close to the (common) cathode lead of the lower LED.

17. Insert the stripped end of the red wire through the hole in the base and the hole in the landing.

18. Cut off a 3/8" piece of the discarded red insulation. Slip this piece of insulation back onto the red wire, until it contacts the landing.

19. Solder the red wire to the anode of the upper LED.

20. Clip off all remaining excess lead lengths.

21. Slide the small piece of insulation until it contacts the anode of the upper LED. The insulation should be positioned so that it insulates the wire from the other two wires where they all come together at the lower LED.

22. Insert the ladder into the ladder holes in the base. The top rung of the ladder should be just below the base of the platform. Arrange all wires so that they hug either the inside of the ladder or the back of the mast. Glue ladder into place at the platform.

23. Insert several small pieces of the stirring stick between the mast and the ladder, pushing the wires against their respective surfaces.

24. Glue the wire to the ladder and the mast in several places, being careful not to glue the sticks to the wire. Remove the sticks when dry.

25. Push the insulation (below the base) until they contact the base.

26. Fill all holes with putty. When dry, sand smooth.

27. Clean the signal with denatured alcohol to remove any oils left from your fingers.

28. Mask the target, including the front of the small collar.

29. Airbrush/brush the back of the LEDs with black paint, so the light from the LEDs doesn't show through.

30. Airbrush/brush the whole signal with silver paint.

31. Remove the masking tape from the target.

32. With the brush, touch up the front of the small collar with silver paint.

Your operating block signal is complete.