Decoder Installation into an
Rivarossi HO FEF 4-8-4
Not exactly to Scale!
Current draw of factory headlight: 33mA @ 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. On the FEF, all you need remove is a screw in the front and in the back. 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.
Then you may say to yourself, "How am I going to put a decoder in this!" In the end, this was about the easiest Rivarossi so far.
Please note that the electrical terminal shown to the left of the motor shaft above is really under the motor shaft. I just moved it a bit for clarity.
Fortunately, the motor is already electrically isolated from the frame - once the wires are removed from it, of course. The headlight really isn't attached to the frame, but there are a few simple things you will need to do to electrically isolate it. It's easy, so you need not be tempted to use a grain of wheat bulb nor to use the headlight at half brightness.
Two screws hold the weight in. Remove them and then remove the weight. It may not seem possible to get the weight out through the front, but it can be done by rotating the weight about 45 degrees.
To isolate the headlight, do these three simple things:
Cut the blue wire (the headlight return wire) to at least 2" long and solder it and the piece you just cut off to the brass rivet. Do not do this soldering with the rivet in the weight! You will have a miserable time and be unsuccessful in trying to solder with the rivet in the weight. The weight will suck away all the heat. Excessive effort to heat the solder may damage the decoder. The extra piece of blue wire soldered onto the rivet is for rear lighting. Even if you are not going to install rear lighting, solder the wire on now while it is easy to do. I will discuss what to do with the other end in a little while.
Now tape all the remaining wires, including your new piece of blue wire to the side of your decoder. If you tape them to the top, you probably won't be able to get the decoder in the locomotive. Don't groom the wires tightly as you bend them back. You will stress them and they may break.
Slide the white wire through the locomotive to the front. Put the weight in the locomotive. Put the rivet into the weight. Screw the weight back in. Now push the decoder into the locomotive above the weight with the end of the decoder that has the wires coming out towards the front. The actual wires themselves should be towards the back.
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!
On the rear tab, you will not be able to leave 1.5". Leave all you can. Grab the insulation with a pair of pliers and strip about 0.25" off. The pliers will keep all the insulation from sliding off when you strip it. If you still manage to have the insulation slide off, you will be able to slide it back on.
Go ahead and screw your locomotive back together. Yes, the headlight wire is still dangling.
Now make sure there is no way the weight is still touching what is left of the metal tab on the motor mount. It probably isn't, but it's easy to check. Take an ohm meter and touch it to the weight. Then touch the other probe to all eight of the driving wheels. If you never get an ohm reading (actually known as a continuity reading in this case because you are looking for essentially zero ohms) you did good!
Solder the end of the white wire to the bottom of the headlight bulb. Put the bulb back in the locomotive.
Run the yellow wire and an extension of the blue wire 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. This includes the new blue wire for the future rear headlight. 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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