I have a Lifelike (not Walthers ) Y3 that I mounted the head light to the smoke box and moved the bulb behind it, however at low speeds the bulb is too dim. Can I just solder a LED to the PCB on this engine or is the voltage too high? Is the PCB just for directional lighting or is it a voltage resister for the bulb? Has any one changed this to a LED?
A typical LED should have a resistor in series with it so that I will not burn out. 1000 ohms would be typical. A lower value would make the light brighter. The polarity is also important so the light comes on when the locomotive is moving forward.
You NEED a resistor in series with a LED. LED's are polarity sensitive, so the only light when power flows the right way, but will not harm them when power is revered, they just won't come on. On a typical N-scale train you would want an 820 ohm resistor to get the maximum brightness while limiting current to safe levels for the LED. and with good quality LEDs it will give you a pretty good level of light at slower speeds, but there's not perfect way to always have a LED full bright on a DC layout, on DCC it's easy since track voltage is always the same, 12 volts typical on N-scale, 15 volts red line.
There's a thing called a voltage limiter that can protect LEDs provided the amps stay within range. They do a better job of lighting the light at low speed on DC power, but they're bigger than resistors and harder to hide in an N-scale body.
