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I own a Mantua tender engine and want to add a back up light to the tender. Using DC and grain-of-wheat bulbs. Is there a simple PC board or a wire schematic for this? In reverse, I want the tender to light to come on and the front light to shut off.
 

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Yard Master & Research
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LEDs are more fun but a simple diode will work. Connect in series with the bulb and test which rail is positive when the engine is forward. A 1N4001 will work.

Pretend the LED is a bulb and the resistor is a diode. Ignore the other thing. It will not matter on what side the diode is. The direction will determine which wires are connected to which rail to get the desired result.

 

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Yard Master & Research
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The Model

I have two 6 volt bulbs in series for a 12 volt difference. AT a full 14 volts it was bright and I added 150 ohms as a dimmer. Depending on use you may not need any but I say 150 is the max. THe diodes are shown and notice the bars on them are reversed. SO the positive current is originating from the far side through the bulbs and into the diode. On the right the positive current is blocked by the diode.





I then mounted it on a board for stability.



CIrcuit description, Track power to two diodes to a set of lights for each diode, then to a common resistor and back to track.

That is a forward and reverse light. Remove one diode and the forward will stay on always and the reverse
will work correctly if your wires are correct. If not then switch the feed wire connection to the track.

 
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