I believe the bulbs are 1.5V, you can check with meter. There may be a pad on the chip for 12V(or track voltage) so look for that. I would not change as I like the bulb look. If you're good at tracing boards you might be able to find another voltage spot.
Once you know what you're dealing with on the board as far as voltage sources, then you will know which way to go in wiring in the LEDs.
Richard
You are pretty much going to have to pull the factory board and set it aside. The factory board is regulated to 1.5 volts to drive the bulbs directly and won't drive your LEDs which require a bit over 3 volts to operate .... which is something else to consider as your LEDs won't illuminate as quickly as the bulbs on DC.
Something else to consider is whether you want your LEDs to be directional in the engine (change which end is on depending on direction) or on in both directions. If you want them directional, you can just connect them straight to the track pick-up leads through a 320 to 390 ohm resistor on each LED. For directional, the + lead of the front LEDs would connect to the right rail and the + lead for the rear LEDs would connect to the left rail.
If you want them to be non-directional, use a bridge rectifier wired backwards. Attach the truck leads to the AC terminals on the bridge rectifier and the + and - terminals to the LEDs through the resistor.
Mark.
¡ uʍop ǝpısdn sı ǝɹnʇɐuƃıs ʎɯ 'dlǝɥ
Thanks guys for your help BUT,I have decided to go and replace the board with a tsunami DCC board.All I need now is to find out what size and where to buy the smd led for ditch lights and how to hook up.I have replaced about 5 boards but never changed the bulb types from bulb to led.Seems that their are too many ways others do this .So much that my head spins.The board is a GN 1000 that they recommend but I really like the sounds of the Gevo.Any help would be appreciated esp when the board has a +14 common.
GN refers to the board format not sound files. Call Tony's train exchange and tell them what you want to do. You can get a board that handles LEDs, will work in your loco and have the correct sound file.
http://www.tonystrains.com/
Thanks richard.Will try that.
The GN-1000 is an Athearn replacement board. You don't want that if you are converting to LEDs. The GN-1000 has the same regulated 1.5 volt outputs so you can use the Athearn bulbs. Get an AT-1000 board with the sound file you want. The AT-1000 board has full voltage outputs on the function tabs, so you will need a 1000 ohm resistor on each of the LEDs.
Ulrich make Athearn replacement LEDs which are surface mount LEDs mounted to an optic strand made for fitting straight into the Athearn headlight openings, but are rather costly ....
http://www.ulrichmodels.biz/servlet/the-DCC-Components-cln-LEDs-and-LED-Lighting-Kits-cln-LEDs/Categories
There is a seller on ebay (Big Al Mayo) that actually makes a great kit that does the same thing and will do two engines for less than half the price (get the warm white ones) ....
http://www.ebay.com/sch/sellsellitall2011/m.html?_nkw=&_armrs=1&_ipg=&_from=