I have one of the newer Rivarossi Big Boys with the can motor and flywheel drive. I had a problem reversing it and when I opened it up I found it had a decoder in it (I bought it on Ebay and wasn't told it was DCC but noticed the box was marked 'Digital'?). I removed the decoder, rewired it and it worked fine on DC. NOW I am running DCC and installed the decoder back but when I did I couldn't find where the blue wire was attached to the engine. I know it is the common for the lights and the white and yellow were wired together (there is no back up light!). Does anyone know where the blue should go to from the decoder? I tried to ground it to the chassi/weights but it shorted it out. The headlight doesn' t work now and I know it is because the blue wire is not connected to complete the circuit. Any help would be appreciated, as always.
Bob
Life is what happens while you are making other plans!
Blue wire doesn't connect to the motor or the frame. As you found out, doing so shorts it out. Blue wire is + common for all of the functions. The colored wired white, yellow, etc. are negative for the functions. So to connect a headlight, blue goes to one side of a bulb or the anode of and LED. White goes to the other side of a bulb or the cathode.
Unfortunately, now that the blue wire has been shorted to the frame, the circuit on the decoder is probably blown. Try hooking it up properly to the bulb but I'll bet it is damaged and won't work.
Martin Myers
Bob,
If I'm understanding you correctly: One end of the blue wire is the common for the front and rear light; the other end is attached to the common pad on the decoder - i.e. so that when you press "0" or "headlight, the front and rear headlights go on or off.
Bob, which decoder do you have installed on your Big Boy?
Tom
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On the Rivarossi bigboy, the blue wire was never hooked up in the first place.
the sleeve of the bulb is in direct contact with the metal chassis, and that contact completes the circuit. ( what would be the Blue wire connection)
the white and or yellow wire connects to the center insulated contact via the black wire that feeds thu to the motor compartment, and the bulb operates .
even though the blue wire is the positive + lead for the function, think of it as the ground wire that stays connected all the time.
the function wires are the hot leads that are switched off and on by the decoder as needed.
So your asking, if it;s the ground, why did it short, well the decoder has a rectifier that converts the fuction output from AC to DC for constant polarity, so if the blue wire is connected to the chassis, it creates a short when the AC phase is opposed during every cycle.
inside the bulb that short heats the filiment, and we have light..
If the headlight has one side connected to the frame, the blue wire is not used. The light is using half wave power. To use the blue wire, the light would need to be isolated from the frame so that its only electrical connection would be to the blue wire and the appropriate function wire. Connecting the white and yellow wires to the same terminal is OK. That means the light will be lit forward and reverse.
The blue wire is used (full wave) if special lighting effects are to be used. If the light just needs to be on, the blue (+ common) is not needed.
As I posted previously, connecting the blue wire to the frame fried the function output. Motor output may still work, but the functions will be inoperable.
BTW, the one term I would not ever use to describe the blue wire is "ground"
Just to update; the decoder is the one that came with the original engine and I don't know what brand it is, possibly Marklin? After I touched the blue wire to the chassis/weight it sparked and the DCC system stopped momentarily, and then restarted.. It runs fine now but doesn't have the headlight working, even using the 0 function on my controls. As some of you suggested, I may have fried the light function on the decoder. I will try to get to the bulb and see if it works iwth direct voltage applied to it. If it works then I will have to assume that the decoder functon is fried and will replace the decoder.
Thanks to all,