what size led ?

What size LED's are people using in HO locomotives for head lights ? Thanks for your help again :)

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Well, lets go see what Miniatronics has available:
3 mm .118" that's a wee bit under 1/8 inch.
5 mm .197" that's a wee bit over 3/16 inch.
That 5 mm one is going to be similar in size to the Athearn bulb that you are replacing, however, depending on what you do, and how you do it, the correct size LED is going to be determined by your personal preference. Both will work equally well. In something like an F unit, I would probably favor the 5 mm one. In a Geep, I would probably opt for the 3 mm size.
If you've never done anything like this before, don't be shy and undecided. Go ahead and take the plunge. Once you do it the first time you will see how easy it is. You can get LEDs cheaper than Miniatronics sells them, but the advantage of buying the Miniatronics LEDs is that all the guesswork has been removed from the process. You know what the LED will look like, and you know that the resistor is the correct value. So, unless electronics and mathematics is your hobby, Miniatronics is the way to go.
Froggy
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thanks again Froggy :) I hooked up an old athearn GP 35 tonight with a MRC decoder and it worked fine. I dont like the Brightness of the Athearn head light so i'll be looking for the led's to install tomorrow. I'm running the new Prodigy advance and it seems pretty simple compared to the upper end DCC systems. it was simple to program the 4 digit address (locomotive number). Thanks again :)
Froggy wrote:

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Rather than bothering with a LED, why not just put a resistor in series with the light bulb? Decreasing the brightness of the bulb will lead to a much longer life for the bulb in addition to gettign that proper yellow glow of a railroad headlight.
-- Yeppie, Bush is such an idiot that He usually outwits everybody else. How dumb!
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