Decoder Installation into an
Not exactly to Scale!
Current draw of factory headlight: 33mA @ 12V. Locked rotor stall current: 1.2A @ 12V.
For your information, I used a DH83FX decoder for this installation.
Initially, the most challenging thing about the conversion is figuring out how to get the locomotive apart. See the parts diagram that came with your locomotive on how this is done. See the section on openning the Centipede Tender w/o a jack-hammer, radial arm saw, nut cracker, or whack-a-mole mallet if you wish to use a rear head light.
Look at the drawing below. Remove all the wires shown in the above drawing. Note which hole the headlight wiring passes through the boiler. You will need to know this when your replace it with a grain of wheat bulb.
Fortunately, the motor is already electrically isolated from the frame - once the wires are removed from it, of course. Unfortunately, like many steam locomotives, the head light is grounded to the locomotive's frame. Use a grain of wheat bulb so you won't have to worry about isolating the exisiting bulb from the frame.
Unfortunately, the Challenger pilot truck walk way is not removable; at least I wasn't able to find a way. If you follow my tips for the Big Boy and attempt to do likewise to your Challenger, you risk almost certain damage to your Challenger. Also, when you loosen the power contact for the bottom of the headlight bulb, a steam pipe falls off topside. Boy, was it a pain to put back!
Remove the bulb contact and it's corresponding wire. Put the screw and washers back to hold the steam pipe in place.
Install the decoder wired as shown. You may solder the appropriate wire to front and rear power pick-up tabs. However, these housings are plastic. If you are not an expert solderer, you will melt it and you will probably short out your locomotive, damage your decoder, and otherwise ruin your day. It's okay to "chicken out" here. If you are not sure you can complete the solder connection in under five seconds, start clucking! It's for your own good! Cut the wire 1.5" or further from the solder tab on the plastic housing. Solder your wires to these wires being sure to have slipped a piece of heat shrink tubing on first!
Replace headlight with a grain of wheat bulb. Snake the wires through the hole in the boiler that the old head light used. Before doing so, you will want to make sure at least 3" of the grain of wheat bulb wires are black - they will be noticable if not blackened.
If you intend to use a rear headllight, you will probably need to drill a hole in the grate area of the firebox underneath the cab floor. Run the yellow wire and an extension of the blue wire through the hole and out the back of the locomotive. For futher instructions on the rear tender headlight, like how to get into it, click here.
Take all the decoder wires you have left over and cut the ends off of them so that there is no exposed wire. Put all of them inside a piece of heat shrink and shrink it. Do not solder them together! While cutting them flush almost guarantees that they will never short to anything, especially the frame (which is tied to one of the wire pick ups), almost doesn't count. You need a guarantee. If no heat shrink, then electrical tape - though electrical tape leaves a messy residue. If you are still thinking about not covering these ends, think of these two things: How much is that piece of heat shrink tubing worth? How much is a decoder worth?
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