I think I asked this before, but I never got a good answer that I can remember. I may have got a good answer, and just for got as well.
What spawns this question this time is Simon 1966 was so kind to up grade a kite bashed Dash 9 to DCC for me. He installed new bulbs but got the math wrong on the resistors and they blew shortly after I got it back.
I don't want to burden Simon with fixing the lights. Shell is a Train Line and there are ditch lights. Decoder is a TCS T-4X.
Sorry to be such a pain.
Ken
I hate Rust
For bulbs you need to know the voltage and current. Same as LEDs actually. Knowing those two things, and the voltage output of the decoder, you can calculate the required resistors. 1.5V bulbs are often 15 or 30ma, but you need to know which. Otherwise, start big and gradually use smaller values until the bulbs are bright enough.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
Ken, I used 1K ohm originally and they were way too dim. They were all I had around at the time and while I knew they were too high for the application, I generally like to run bulbs with a higher resistor to get a longer life out of the bulb. The resistors I used in the final application were 560ohm, Brightness seemed about right and since I tested the loco on my layout several times and they worked fine, so all seemed to be in order. Probably should shoot for something in the 700ohm range for replacement bulbs of the same type.
Simon Modelling CB&Q and Wabash See my slowly evolving layout on my picturetrail site http://www.picturetrail.com/simontrains and our videos at http://www.youtube.com/user/MrCrispybake?feature=mhum
Your voltage is probably a bit lower - Zephyr is about 12.5 volts, DB150 on HO is about 14.5. And whatever you do Ken don;t flip it accidently to the O/G setting - 20 volts to the track.
If 1K is too dim and 560 blew it, try 680 or 820. 820 first, if still too dim drop to teh 680 (standard values for 10% resistors)