I own three Proto Heritage 2-8-4 steam locomotives, an NKP, a Pere Marquette (PM), and a C&O.
A few years back, I replaced the burned out incandescent rear lamp in the tender of the NKP with a 3mm Miniatronics Yelogo LED and installed a 3mm Miniatronics Yeloglo LED in the engine head light housing.
A few weeks back, I noticed that the incandescent rear lamps on the other two 2-8-4s (PM and C&O) were burned out. So, I replaced those rear lamps with Miniatronics 3mm Yeloglo LEDs. At that point, I couldn't help notice that the incandescent headlights in these two steamers were very dim, especially compared to the rear lamps. So, I set about to replace them.
I had no problem with the Pere Marquette because, like the NKP, the LED fit nicely into the headlight shround. However, I ran into problems with the C&O. On the NKP and the PM, the headlight shroud has the lamp fitting directly in the center of the shroud, in line with the female fittings in the boiler that accept the two lamp wires.
But, on the C&O, the lamp fitting is at the bottom of the headlight shroud. Because the two lamp wires have to feed through the boiler weight, this made installation of the 3mm LED impossible because it prevented the headlight shroud from fitting into the boiler shell.
My solution was to install an SMD LED (Surface Mount Device). This miniature LED is slightly smaller than a grain of wheat and is powered by two #36 wires. To get such small wires to fit snugly in the female fittings, I had to solder the #36 wires to small lengths of 22 gauge wire which then fit snugly into the female fittings.
I am starting this thread in order to inform others who wish to replace this headlight how to go about doing it. Not an easy task.