Before: The first thing you notice about this GP-7 is the poor headlights and the brightness of the number boards. The number boards put out more light then the headlight itself and the color is not as good as the picture implies.
After doing some research I decided to try some of the new golden white LEDs that I had read about first in the GP-7 and RS-11 which has the same problem. I contacted Jim Hines at Richmond Controls and ordered a few of his 3mm golden white LEDs that have a very small capacitor and diode attached. I believe the additional components are recommended to protect the LED which are more sensitive to voltage reversal then the old LEDs. The new LEDs arrived with a shrink tube type hood that enclosed most of the extra two devices. Jim Hines is a expert on LEDs and he has some very nice products at Richmond Controls.
The LEDs required a little creative mounting in the old Atlas RS-11 engine
as the RS-11 shell sits on an Atlas RS-3 chassis. This meant that they had
to be mounted higher on the chassis to align better with the headlight
holes. I mounted the LED on the opposite side of the
circuit board. A 1.8K limiting resistor was use to limit the LED to the right
brightness.
I simply unsoldered the old yellow LED on each of the small light boards and replaced it with Jim's golden white LED on the GP-7. The limiting resistor was also changed to 1.8K. I did extend the mounting of the LED a little more past the edge of the card so it would sit closer to the plastic lens inside the hood. I also made a little "V" shape in the split frame metal so the LED could rest in it and there-by keep the light board level.
After: The much improved headlight results of the RS-11. You can even see a little headlight reflection on top of the rail at the right. The GP-7 engine came out with the same good results. You will notice that the engine number boards have been painted over, inside and outside, with black paint as I could not find an effective way to minimize the light intensity going to the number boards via the triangular plastic lens that sits inside the hood at both ends.
The headlight was not lit in this picture which shows the new number boards. They were done using a great technique documented by John Sing at his site located at:
http://home.comcast.net/~atsf_arizona_2/Easy_N_Scale_Locomotive_Numberboards.html