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Discussion Starter #1
Hi,

I have a Helvetia Trans Europ Express train set and the dummy loco needs a functions decoder in order to manage lights change according to the direction of travel.

The main loco is equipped with a DCC sound decoder, I believe it's an older ESU lokpilot (not sure as I bought this second hand without the manual, I suspect a V3 or V3.5).

The dummy loco has no connector to just plug-in a decoder thus as I am inexperienced with this process I require your input, if possible.

I am attaching some images so you can see how the wiring is done inside.

It has 3 bulbs and diffusers, one for the engine room and two for the headlights/stoplights. The one in the engine room should be on regardless and only the other two should change.

In regards to the decoder, I was thinking to use either an Uhlenbrock 75900 or an ESU 54620 functions decoder (apologies for the EU brands used).

Thank you in advance for your time.
 

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I think the ESU model is a good choice. It can be synchronized with other Lokpilot or Loksound cards and can use the same address as the main card for control of lights in both the powered unit and the dummy unit.
 

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From the looks of your images, that circuit board is doing nothing but switching the lamps depending on the direction of DC power. You could probably remove it if you're tight on space. Also consider switching to LED lights (you need to include a resistor, but there are many online calculators to tell you what resistor size to use). And sorry if this is obvious (I hope it is), but don't forget to insulate any exposed parts of your decoder since the frame of your loco is metal.
 

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Discussion Starter #4
Appreciate the input Shdwdrgn. I will take it with me this week to a local store to ask for some guidance there as well, they've always been super helpful.
Space is no issue in this one as it contains nothing mode inside except for what you can see in the images. Definitely will isolate the decoder, thanks for reminding me about that. :)

If possible, I would like to keep the bulbs. I am a big fan of this type of light and warm light in general (especially for trains than ran in the 60s/70s). The other reason is to not have it look different in color temperature compared to the rest of the train which has the same type of lights installed (5 coaches and the main loco).

The higher power draw compared to LED shouldn't matter as I only have two main tracks and a loco shed so can't run many trains at once, plus everything else ( semaphores, points, street and building lights etc) will be powered by separate sources.
 

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It should be a simple chore to install an inexpensive
DCC decoder in that dummy loco to control the lights.

You would connect the wires from the truck wheel
pickups to the input of the decoder. You would disconnect
the headlights from the existing PCB and run the
Decoder headlight wire (decoder instruction will show which color wire that is) to the bulb socket. You would also disconnect the wire of the rear light from the PCB and connect the
decoder backup wire. Headlights and rear light would
each be connected to the blue Decoder light common.

The new decoder would come using 3 as it's address.
Change that to the same address as the powered loco
the dummy will accompany. Thus, what ever command
you give the powered loco the dummy lights will
light as forward or backing. You also could turn off the
lights using the same command as you do for the powered.

Note: The light output of all decoders is 12 v DC,
the blue common wire is Positive. If those unidentified
components in the PCB are resistors you should include
them in the light circuit from the decoder to match
bulb voltage to the 12 v. If they are capacitors they should be disconnected.

It appears that you have plenty of room for the typical
near postage stamp size decoder. Do not get a PCB
decoder as that would require effort to install.

Don
 

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Just in case you DO get to the point of installing LEDs some day, keep in mind there are specifically "warm white" LEDs available now that look very similar to bulbs. Nothing like the older style white LEDs that had a definite blue tint to them!
 

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Discussion Starter #7
Thanks Shdwdrgn.
I will keep in mind and look for this. My electronics skills are really not that good to make the change to leds by myself as they require other components added in certain ways unless I find prefabricated ones that I can cut at the desired length.

DonR

Thank you for this detailed process description.

I will be heading soon to buy a decoder and start doing the plus I need to identify the two components as you say so I will most likely take the loco with me.

Once I finish I'll update the post with all the details just in case anyone needs the info in the future.
Best,
 

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Actually it's not as hard as you may think it is, and LEDs are great to use for other purposes such as indicator lights. Basically all you do is solder the resistor to one leg of the LED (it doesn't matter which one) and then hook up power. If the LED has a flat spot around the base, that side is the negative.

For a 12v power source and standard-brightness LEDs you can probably use any resistor between 600 to 1000 ohms (1k resistors are extremely common), but if you want to dial it in for maximum brightness then just ask for help here and we can assist you with the calculator that I mentioned before.

I actually need to replace the light on my new loco... apparently it came with an LED installed but no resistor, so I've never seen it come on. But I happen to have a bag of 3mm warm-white LEDs just for the locos I already converted. One nice thing about LED's, you can get a large bag of them for the same price as a single bulb. :)
 

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LEDs can be very cheap, i just got in some 5mm flat top white, with a viewing angle of 130 degrees ... price was low at $2.88 for 100 of them , including delivery and in Canadian funds!
 

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Don't forget the resistors for the LEDs! (So in the end you need a soldering iron, some solder, your handful of LEDs of the color of interest and size such as 3mm as suggested above, some very thin gauge wire, some shrink wrap... Maybe a magnifying glass, something to hold the work. So for some pretty good instructionals not directly related to model trains as well as possible parts try: adafruit.
There are lots of general source for electronic parts besides this.
 
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