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I have six, K Line Heavyweight passenger cars with MDK-034 Streamlighting boards in each car.  I want to run those cars with my Legacy K4 on normal command voltages.  I have had three cars go dark in a week and I replaced two bulbs in each car, each time.  I know these boards are wired so that there are two sets of circuits with six bulbs on each side wired in series.  I think they are 2.5 volt Christmas light bulbs.  I have bunches of those bulbs but I was wondering if there is a safe way to put a resistor into each circuit to lower the voltage to a lower level, yet keep the cars adequately lit?  Also, what would be the best sized resistance?  Also, are they really the same bulbs that are used in Christmas light strings?



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I've tossed dozens of these boards, they provide decent lighting, but Chris is correct, they suck up power like there's no tomorrow!  Trying to lower the lighting with resistors is a poor way to do this, LED's will give you better lighting and reduce the power consumption 90-95%!  Did I mention they're flicker-free and have intensity adjustment to tune to the exact light level you desire?  They also include DCS signal protection so they won't affect the MTH track signal.

LED Lighting Regulator


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  • mceclip0
Last edited by gunrunnerjohn

One per car, there is supposed to be a link there to the instruction sheet, I'll have to get Bill to fix that.  Here's the instruction sheet for the modules.

Pass Car Lighting Module Documentation.pdf

You can also reduce the overall height to around half an inch just by folding the tab on the regulator over the cap.  I use a brand of regulator with the thin tab for that very reason.


Last edited by gunrunnerjohn

The LED strips I bought had a backing tape that I pealed off to reveal a contact glue surface. Just stick them to the inside roof of the car. If you want a little extra security, add a little hot melt dab across the tape after you have it stuck to the roof. BTW, measure and solder the leads to the tape first! It's easier that way... Speaking of solder, flux is your friend! I put a little on the pads of  the tape and then quickly melt a small blob of solder to the pad. Strip and tin the leads, add flux, and then hold the wire in place on the tape and touch the soldering iron to it. The solder quickly melts and makes the joint.



Like Chris says, normally I strip all the existing stuff from the ceiling and just stick the LED strip up there.  For full some cars, I've been known to use the plastic assembly in MTH cars to hide the LED's from side view.

A few threads on LEDs in passenger cars.

LED Lighting Upgrade for MTH Full Dome Car

Passenger car LED lighting (Again)

Passenger Car Lighting Experiment

MTH Amtrak Superliner LED Upgrade in Pictures

Notice how I used the plastic bulb holder strip to hide the LED strip.

For observation cars with markers and/or tail-lights, I tap off the LED strip and use a current balancing resistor to adjust the light level of the added LEDs.

Reading Crusader Observation Car Lighting N4

Here's one of my heavyweights lit with yellow LED strips, really looks like the real thing.

PRR Madison with Yellow LED

For observation cars with markers and/or tail-lights, I tap off the LED strip and use a current balancing resistor to adjust the light level of the added LEDs.


PRR Madison with Yellow LED

@gunrunnerjohn, is there a specific value resistor you use?  If not, how do you calculate the value?  Also, what LED's are you using for the markers/tail lights?

I've not done the marker/tail lights, so I need to up my game.

Well, you can "calculate" it, but truthfully, I eyeball it and just swap values until I like the effect.  Generally, the resistor will be between 470 ohms and around 2K.  If you only have two red marker lights on the sides, it ends up being closer to 2K.  If you have three lights, sometimes it'll be 470, 680, 1K, etc.  The value will also depend on how bright you run the interior lights.

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