I’m more or less a complete newbie of less than a month when it comes to model railroading. With that in mind, I would appreciate any help with my new Athern HO scale GP40-2 that I received today. It runs beautifully–so smooth and silky even at the slowest setting. Very nice.
However, there’s a light bulb that is quite visible through the cab windows:
I would have thought that this is the light bulb that powers the headlight and also lights up the engine number. Is that indeed the case, and if so, is it something that I–keeping in mind that I’m really, really new to the hobby–can fix, or should I send it back to Athearn?
Athearn has alway had the “fire in the cab”. Only the Genesis line has the light source up where it belongs. All Athearn RTR GPs, SDs, and kits have it in the cab.
There are two ways to fix it. The first is to get a new 14-volt grain-of-wheat bulb with attached wires and relocate it up near the lens in the cab. The second option is to make a constant-lighting circuit with a 1.5-volt LED and place it near the lens in the cab.
Well first of all… welcome to the wonderful world of model RR’ing. You will find this a great hobby… exspensive, frustrating…but great! To answer your ? about the headlight, That is the way it supposed to work. it is supposed to represent lights in the cab as well as ur headlight and # boards. Are you running DC or DCC? Most DC units are like that and get brighter as you turn the dial, unlike DCC witch have smaller bulbs placed throughout the locomotive.(meaning directional lighting, numberboards, mars lights and ditch lights) that come on and stay on. I have a GP38 that came from the factory DC but i changed it to DCC. I still only have 1 lightbulb and its in the same spot as yours is. The light is fine as long as ur not lookin to be prototypical (modeling after the real thing). I hoped that helped alittle. Enjoy your athern, they run great!
The Athearn GP’s all come this way from the factory. Light showing in the cab windows is not realistic. You must have noticed how the dome light in a car casts reflections on the windshield and nobody drives with the dome light on after dark. The locomotive cab is the same deal, the crew wants the cab dark so they can see out the windshield.
I make a ceiling for the cab from Radio Shack vector board and mount a constant lighting circuit and one bulb in the cab ceiling. This bulb illuminates the number boards and and short hood headlamp. Then I mount a second bulb in the long hood to illuminate that headlamp. A short piece of tubing glued to the inside of the long hood roof serves to position the bulb properly.
The constant lighting circuit is pretty simple. Silicon diodes show a constant 0.7 volts across them, no matter how much current they conduct. Two such diodes in series will yield a constant 1.4 volts, just enough to light a 1.4 volt incandescent bulb. You place the two diodes in series with the motor. Then motor current going thru the diodes creates the 1.4 volts to light the lamps. The 1.4 volts stays steady at 1.4 volts no matter how much track voltage or motor current we have. Other benefit, you can ease your throttle down to a point where the motor lacks the juice to move the train, but there is enough juice to light the headlamps. You can have a train stopped with the locomotive headlamps on. Very effective.
To make the circuit work when track polarity is reversed, just add a second pair of diodes facing the other way. Any kind of diode from your junk box, or an old electronic appliances will work. Or, Radio Shack sells a small “full wave bridge” which is the necessary four diodes in a single package.
I have three Athearn GP’s with the home brew constant lighting. Consisted together they look nice pulling heavy freights
Thank you very much for the excellent and informative instructions. I’m going to bookmark your post and return to it in a few months when I’ll be (hopefully) more comfortable with taking trains apart and working on innards, and also more knowledgeable at working with miniature electrical components like the ones you described. They sound great, especially the “train-stopped-with-headlamps-on.” I’ve only been able to semi-achieve this with panning the camera along the train’s movement and shooting at high enough ISO to minimize blur. Not very effective.
I’ve recently purchased 2 different Athearn RTR’s. 1 of the New RS-3’s and the other is a GP-38-2. The RS-3 has the headlights in the correct place, and a DCC plug. The GP-38-2 has the “fire in the cab” and no DCC plug.
