Yesterday I dropped two TCS A4X decoders into a now older but DCC-ready Genesis F3A/B set (ATHG 2501A). Out of the box, both of the headlight lamps on the A unit were wired in parallel to the center pair of tabs on the left end of the stock light board. I’d like to replace those stock Athearn lamps with TCS 3mm golden white LEDS out of the stock that I already have on hand. As the A4X has a gyralight function, how do I attach these LEDs in a way to allow that to function on only one (the upper)? I can’t conceive how a simple parallel attachment to the board would allow for that.
The TCS website indicates that the A4X has the appropriate resistor(s) on board for LEDs. A photo of a proper light installation would be appreciated as the TCS installation photo shows only a single incandescant bulb installed in the hood.
My only TCS decoder is in a steam locomotive so I have no knowledge of how the TCS works. I have MRC 1730 decoder in my E7s and they use a pair of LEDs for the MARS light.
I ended up making dual LED MARS lights for all of my E7s and they work very good for me. Here is a link to the MARS LED on my Blog.
The headlight LED would connect to the center terminals, that’s F0F and the blue common. The second LED needs to be soldered to a pad on the board, there will be at least 4 of them, for F1-F3 (plus FOF and F0R, that’s your 6 functions) The decoder instruction will show where the solder points are for the extra functions.
The link to this diagram is exactly the same as the one that should have come with your A4X decoder. (Looks like Henry provided the link to the same diagram.) It shows how to wire both incandescent and LED lights. Since you want to use LEDs, you want the bottom diagram.
Green in the diagram goes to lighting function 1 & purple goes to lighting function 2. Your front LED headlight with the mars lighting can be connected to either of those. (Remember: The anode connects to common; cathode to function pad.) You can also remap that function to any of the function buttons on your throttle - i.e. except for F0, which is your headlight function.
