I was also unsatisfied with the brightness of the lights on my Kato SD70MACs and SD90MAC. It is the clear pieces of plastic that are the problem. They diffuse a lot of light. You can replace them with fiber optic strands if you are feeling adventerous, but the easy fix is to substitute a brighter LED.
Although LEDs certainly CAN be dimmed, they shouldnt be on your loco unless you have a decoder installed and have programmed the light to be dim.
A lot of people say LEDs arent as good as bulbs for flashing lights becuase they dont dim as well, but I think they work just as well as long as you program to accomodate the LED. LEDs light up with less power than bulbs, and you can really only see a change in brightness at the low end of thier power range where as bulbs dim and brighten pretty evenly along thier entire power scale.
Kato uses a single LED and a plastic light guide for the headlight and ditch lights. Substituting a brighter LED is the cheapest and easiest solution, but remember that LEDs are polarity sensitive so you need to make sure you know which pole is positive and which is negative on the old one before you remove it. Flashing ditch lights on one of these models requires installation of separate LEDs and DCC.
I have the same issue on SD40-2, my first Kato, and my impression is that the dim lighting is absolutely terrible and borderline ruins the model for me, will be sticking with Intermountain and Broadway Limited. You are not alone.
Paul
I don't care much for the 'light bars' that many manufacturers use to illuminate the headlights etc. They clearly fail to get most of the light to where it's needed.
My solution is to get rid of the light bars and install 0603 or 0402 LEDs directly behind the headlight or number board lens. In some cases that involves cutting the headlights themselves off of the light bars but that is no big deal. For ditch lights I core the ditchlight housings and install 0402 LEDs right inside them.
It is critical that the LED be aligned properly with the headlight lens. I use 90 second epoxy and I apply power to the LEDs when installing them. That makes it easy to get the LEDs located properly, although you have to be patient and hold the LEDs in place until the epoxy sets. I think that is the most tedious task of all the modelling things I have ever done!
In some cases like F series locomotives a 3mm round top LED will fit quite nicely into the headlight bezel. Unfortunately the curvature of the LED lens isn't ideal so it might look better if the original headlight lens is kept in place.
Don't forget the resistors (says he who has forgotten the resistors on more than one occasion.).
Dave
I'm just a dude with a bad back having a lot of fun with model trains, and finally building a layout!