As part of the recent upgrade to the LokSound - Select Direct decoders I also wanted to upgrade the bulb lights in the Athearn RTR - RDG GP35.
The LED's are a TCS - Golden White 3mm LED.
The installation is fairly easy and can be done in about 30 minutes to an hour. First step is to drill out the holes on the cab for the lights.
The Athearn headlights are slightly bigger than holes for the bulbs, I drill these out with a small thumb drill and ensure the plastic headlights fit. On this RTR GP35 I had to also drill out the opening in the cab to get the LED through the cabin plastic at the back of the number boards.
Once the fit is right I file down the Golden White LED.
Then glue the Athearn headlight lenses onto the LED and shorten the anode & cathode leads. Ensure that headlight lenses are centred over the LED.
Once the CA is cured I place a small piece of heat shrink over the leads. This stops any shorts and also blocks out any light from the cabin interior.
I then fit the LED and lenses into the cab and secure with a piece of Kapton tape.
Then test the LED before replacing the cab shell onto the body shell.
The Golden White LED gives of the perfect colour for locomotive headlights. Be aware though that when using a LokSound - Select Direct decoder like I have you do not require resistors in line as they are installed on the decoder. If you are using anything else ensure you check if resistors are required.