Re-using N-scale Atlas RS1 lightboards in a Con-Cor PA
Sorry for the delay...
OK, first for the general LED wiring info:
While there are some other postings around the internet, the one I found most helpful is an article written by Don Fiehmann that's posted on Tony's Train Exchange:
http://www.tonystrains.com/technews/install-leds-decoders.htm
The first diagram is a huge help. Just two non-technical things I would add to it to help with remembering the various identifications and application connections. Naturally, you can use whatever associations work for you...
1. The anode, or positive lead of the LED gets the resistor. Although the diagram shows the anode lead as "longer", that's only true on a new LED. If you're re-using an LED that's already been installed, the leads have probably been trimmed, so that indicator won't be helpful.
However, each LED is usually made with a "flat" side at the cathode (think "flat cat"), and (looking into the LED) the cathode looks like a "flag".
So: "flat = flag", or "cat, flat, flag"
(I'm allergic to cats, so I associate the cat side as negative.)
Opposite the "flat" side, the LED is "round", and that's the side that gets the resistor.
So: "round = resistor"
(Round reminds me of a scoop of ice cream, which I like, so that's positive...)
2. I would also annotate the drawing with the colors of the standard decoder leads.
I would add:
On the left side of the LED diagram:
the word "BLUE" to the positive (anode round resistor) side, and
On the right side of the LED diagram:
the words "white/yellow" to the negative (cat flat flag)
Sorry, I haven't come up with any good memory associations for the colors..
I knew from previous N-scale installations that the LED and resistor components on the Atlas RS-1 lightboard can be wired to the decoder, so I didn't bother to try changing the resistor. But if you're not happy with its brightness, read the article for other wiring values.
Now for the actual lightboard mods:
For one of the N-scale Con-Cor locos, I dremmeled out most of the tab-side of the lightboard, giving it two very slender "fingers" that sit astride the short protruding ramp at the cab. With the board horizontal and the LED on the underside, I superglued these tabs to the metal protrusion. But first I unsoldered the tab-side of the resistor and bent it up alongside the board.
The other loco was from a different production run, and the protrusion was longer, so I couldn't do the "finger" mod. Instead, I unsoldered the tab-side of the resistor and snipped the board width-wise in about half (just aft of the LED's solder pads). Then I desoldered the LED and pushed it down into the board as far as I could and resoldered the LED to the same pads. After snipping off the excess length of the LED legs, this board now stands upright in the tiny space at the front of the cab.
On each mod, solder the Blue decoder lead to the free end of the resistor. Insulate with either heat-shrink tubing or Kapton tape (whichever is least bulky). Solder the White lead to the LED's (- cat flat flag) pad. Insulate all metal points as needed with Kapton tape.
In both mods, the LED lens aligns with the headlight lens in the shell.
So there you have it! Hope you find it helpful!
-John
