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Discussion Starter #1
So I am looking at converting old Athearn Blue box F7s which I have installed DCC decoders in to LED head light at mars light. I have already installed NCE D13SRJ decoders in my F7 units.

I have a few questions.

What is the ideal voltage range of a LED I should be considering?

I understand that different decoders can give different voltages. I am running a variety of decoders.

Does the Flat top look much different than the normal dome top in the loco?

I am kind of considering buying these..

https://www.ebay.com/itm/100-x-12v-3mm-Flat-Top-Pre-Wired-Warm-Soft-White-LED-Wide-Angle-14v-15v-Prewired/153040394864?hash=item23a1eb1a70:g:rWAAAOSwukVbDGWu:sc:USPSFirstClass!98391!US!-1

... which already have a resistor soldered in them. Just add a 2 prong plug.

How does one handle the Mars light? Just a single element LED?

Ideas?

Thanks,
john
 

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I run DC, but i had to cut those resistors off to fit in my Blue Box F7. Added resistor further down.
 

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there's a LOT of choices ... determine what you want first, viewing angle, etc ..,LEDs by themselves run $2 a hundred or so , and slightly up from there ..
 

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Discussion Starter #7
Way too many choices. So what about the voltage? The monsters dont look like they will work. As they are not large enough for the 3mm F7 bulb opening.

My desire is to have something I can a 2 prong plug too and be able to remove when I pull the top off my loco.

John
 

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All that really matters is what voltage is applied to the LED from the decoder. Does it put out a nice solid 12.0VDC? If so, you can use one of those pre-soldered styles from ebay. If not, you'll want to calculate the ideal resistance.

You may also find the output voltage depends on your power supply and isn't fixed to a nice even value like 12v. Try measuring the output from the decoder while nothing is moving, while a loco is stalled, and when you have more than one loco running. Look for the *maximum* voltage ever read, and use that number for your calculations. If in doubt, round up by a volt or two just to be on the safe side (this may make the LED slightly dimmer, but you probably won't notice).

There are resistor calculators all over online. If you buy from a decent seller on ebay, they will also provide the forward voltage and the amperage used by the LED. You need those two values, plus the voltage supplied by your decoder, to plug in to the resistor calculators. Generally you can use a cheap 5% resistor, and many of the calculators will provide a common value you can easily purchase. For instance, if your ideal resistance were 659 ohms, you can use a standard 680 ohm resistor. The calculator should also tell you if you need a 1/8w or 1/4w resistor (you can go larger with both resistance and wattage, but never go smaller).
 

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There is also a board called a "decoder buddy" you might try. I think it has some unique capability. I just used regular LED's as the decoder drove them with the proper current.
 

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Being the cheapskate that I am I've been buying these strip LEDs and then removing individual LEDs (SMD3568) and installing with a 1k resistor. For about $12 you get approximately 300 LEDs on a strip. You can cut the strip into sections with 3 LEDs and wire directly to 12VDC for areas where more than one LED is needed. They are available in 4 different white color temps. They work great in model buildings too. https://www.amazon.com/gp/product/B002QQ48TK/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1
Here's a model building using the strip LEDs.
 

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So I am looking at converting old Athearn Blue box F7s which I have installed DCC decoders in to LED head light at mars light. I have already installed NCE D13SRJ decoders in my F7 units.

I have a few questions.

What is the ideal voltage range of a LED I should be considering?

I understand that different decoders can give different voltages. I am running a variety of decoders.

Does the Flat top look much different than the normal dome top in the loco?

I am kind of considering buying these..

https://www.ebay.com/itm/100-x-12v-3mm-Flat-Top-Pre-Wired-Warm-Soft-White-LED-Wide-Angle-14v-15v-Prewired/153040394864?hash=item23a1eb1a70:g:rWAAAOSwukVbDGWu:sc:USPSFirstClass!98391!US!-1

... which already have a resistor soldered in them. Just add a 2 prong plug.

How does one handle the Mars light? Just a single element LED?

Ideas?

Thanks,
john
That seems a bit expensive for that kind of LED. I purchased from AliExpress and I was able to buy 1/5 the quantity for about half the price-per bulb.

I've not installed any yet, but I just received 4 different size/colors of pre-wired-resistor-equipped LED's that I'm going to experiment with.

I don't think that a constant perfect 12V is necessary as I've tested them and they work fine with a 9v battery.
 

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Discussion Starter #14
So after a lot of looking, I opted to buy these...

https://www.ebay.com/itm/L123WM-20pcs-Pre-Wired-3mm-WARM-White-Led-Lamp-Light-Set-12V-18V-for-Train/283640986357?ssPageName=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649

... as they are advertised to be in the working voltage range I am reading I need. And they have a 1K resister already installed which alot of the hobby community seems to stand behind.


So it seems like most F7 do not have ditch lights. In southern pacific, only the black widow scheme had them. To have working ditch lights, I am guessing I need to use 2 Aux channels on the decoder. Would this be correct?

Another thing about F units, they have what is like running lights above the number board. Obviously leds are too large. What about fiber optics?

Thanks,
 

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if you just want the ditch lights to come on, only one aux function is needed, if you want them to flash [but not in sync, first one then the other] you would use two functions ..


the LEDs that you showed a link to are bloody expensive for what you get, but yes they will work, and at least are warm white .., even if it does not give viewing angle or even the intensity is not shown either ..
 

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Discussion Starter #16
So where is there good info on using fiber. I am finding info, but nothing concrete.

One of the question is where to find fiber? I was looking on ebay and amazon, finding fiber which emits light out the side. Given what I am doing, I am assuming that kind of fiber is not desired.

Also, what sizes are people using for what features on a F unit?
 

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Discussion Starter #18
Ok, so I bought the 3mm LED as that was what I was reading I needed to buy. They are too small to replace the lenses of the unit. It almost looks like I need a 5mm for one light and something a tad smaller for the other.

I have some older units which are missing the lenses. And it was my intention to install the LEDs in place.

I did buy soft white, am I suppose to glue them to the lenses? Has any one had any luck with that?

If gluing to the lens looks good, I would need to see if its possible to find replacement lenses for the 3 other F7 units which I want to install LEDs in.
 

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most of the time the led is hooked to the decoder / light board and is not glued to the shell or the lens [usually the lens is removed] .. the warm white leds come in either a rounded front or a flat front, depending on application ..
in some cases the led is glue gunned to the case and can unhooked from the decoder / light board , personal preference is all it is ... however in most cases the plastic lens is removed ..
 

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Discussion Starter #20
most of the time the led is hooked to the decoder / light board and is not glued to the shell or the lens [usually the lens is removed] .. the warm white leds come in either a rounded front or a flat front, depending on application ..
in some cases the led is glue gunned to the case and can unhooked from the decoder / light board , personal preference is all it is ... however in most cases the plastic lens is removed ..
Ok, so my decoder has 5 wires that give me 1 pos and 4 channel wires which are my neg. So my LEDs dont solder directly to my board. And these are for my DC conversions where a single light illuminated in the shell and 2 lens allowed light thru.

So it sounds like my only option at this time is too hot glue the LED's to the lenses.

If someone who has worked with Athearn f7's could tell me what size those holes are and if any one knows what fiber cable size to use?

No votes for any kind of super glue or such???

John
 
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