Have you thought about using a LM317 voltage regulator set to 1.5v instead? I've used them (with a bridge rectifier) on DCC with no problems for passenger car lighting before. It also has the advantage of running quite a bit cooler. If the drumhead is the only thing to be lit, you could even use the LM317LZ (small transistor case).
Robert Beaty
The Laughing Hippie
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The CF-7...a waste of a perfectly good F-unit!
Then it comes to be that the soothing light at the
end of your tunnel, Was just a freight train coming
your way. -Metallica, No Leaf Clover
The Tomar drumhead light is a 1.5v bulb. If this car will be run on DCC you can use a resistor per any of the instructions for those bulbs on this or other sites. I went to the low end of the range after much testing to get the light to be visible thru the sign in a lit room. The resistor will work on DC, but the light will only be visible at near full track voltage. Are the markers lit by separate bulbs? Put the 3 bulbs in series and you now have a 4.5v bulb needing a much smaller resistor.
Not too long ago there were a coule articles in MR on constant lighting in cabeese using capacitors. these circuits will also work in the Obs.
Phil
Timber Head Eastern Railroad "THE Railroad Through the Sierras"
Dick
Could you get away with an LED instead of a bulb? I have no clue how the drumheads are lighted but I would think a bulb would melt something. I had thought about useing a TCS lighting only decoder with a couple Bi color LEDs and a little fiber optic strands for markers on my cabin cars.
Pete
I pray every day I break even, Cause I can really use the money!
I started with nothing and still have most of it left!
Gate 5