Bachmann Headlights

[atsfandy]

 Hello I have a Bachmann 4-8-4 DCC on board, the headlight stopped working and I have done everything under the sun to make it work with a new set of bulbs.  I was going to use two headlight bulbs from Athearn R-T-R locomotives,  What does it take to make the bulbs work.  As a side note I understand that the bulbs are 1.5 volt I already verified that the bulbs work.  If anyone can help I wold appreciate

[cacole]

Bachmann used so many different headlight bulbs and LEDs over the years that the only way to know for sure what you have is to tear the thing apart and measure the voltage that is being applied to it.

I have worked on some Bachmann steamers that had a bulb in the middle of the boiler shining through a plastic light pipe to the front, and I have worked on some that have an LED on a small circuit board right behind the headlight lens.

Most non-DCC equipped Bachmann's with an incandescent bulb used a 16 Volt bulb.  With the DCC on-board models, it's probably a lower voltage.

There may be as many as 3 circuit boards involved, as well as the decoder.  On some Bachmann models you have a circuit board in the tender, there is one that the firebox light is connected to under the back of the cab, and there might be one in the smoke box holding the headlight LED. 

You'll need a resistor wired into the line for an Athearn bulb.  The resistor value will depend on the applied voltage and Amperage draw of the bulb.

[rrinker]

 Have you verified that the original bulbs are actually blown? Are they even bulbs, I was under the impression that most recent Bachmann locos have LEDs, perhaps that is mistaken. If the originals are bulbs, I would doubt the decoder has any sort of limiting resistors built in, so to use the Athearn 1.5 volt bulbs you'll have to add a resistor. That value of resistor you need depends on the current draw of the bulbs, off hand I don't know what it is for the Athearn bulbs or I could tell you what resistors you'll need.

 You say you've tried replacement bulbs already and they didn't work? Which bulbs did you try? If the loco did have LEDs and you used the Athearn bulbs, the resistor that would already be rpesent for the LEDs is too big to work with 1.5V bulbs. If the stock bulbs actually check out as working, then the problem is the function output ont he decoder has blown (or a wire is loose). If the decoder function output is blow your only options are a new decoder or send it in for repair (although you can probably get a better quality decoder for less than the repair cost from Bachmann).

                                         --Randy