Dim headlioght on 4-6-2 K4 Pacific

[tmiller]

Hey guys,

I was able to remove the headlight assembly without any problems. Now, in measuring the voltage for the LED, I measured 1.93vdc. Isn't that a little low for a standard LED, or should I be able to find one to match that voltage?

What I am thinking is to drill out the headlight lens, insert a LED into the assembly, and run the wires down to the current PCB on the frame. Does that sound like a possible fix? Or should I cut the light tunnel off and hope that a brighter LED will do the trick?

Ted

[richg]

The voltage is not a primary concern. The current is. I have put as many as three LED's in series with one resistor and never had to worry about the voltage. I started with 1 k and adjusted up or down a little while watching the current. Brightness can change some but not much.
Some people are putting in Super Bright 20 ma LED's and have to increase the resistance to maybe as much  as 2k.
Some LED's you buy can be a the 25 ma type but again, just watch the current.
Put your meter on DC current and connect in series with one LED lead and the lead from the decoder.
I think I already provided a link or two on how to use a multimeter in model railroading electric.
You want at least 10 ma to 15 ma of current.

LED's are current operated devices.

Light bulbs are voltage operated devices.

Many confuse the two issues. I have known a few who burned out a bunch of LED's as they were thinking light bulbs.

The below is only one link on LED's and bubs as used in model railroading but it should help a lot.

http://www.members.optusnet.com.au/nswmn1/Lights_in_DCC.htm

If you probe the PC board with the voltmeter, you will see about 12 vdc from the decoder and eventually see the same low voltage where the lead to the loco headlight leaves the PC board. Pin 6 on the eight pin connector is 12 vdc from the decoder.

Rich

[Doneldon]

What I am thinking is to drill out the headlight lens, insert a LED into the assembly, and run the wires down to the current PCB on the frame. Does that sound like a possible fix? Or should I cut the light tunnel off and hope that a brighter LED will do the trick?

Ted-

I wouldn't put a brighter LED in your loco because you may wind up with some of the light leaking out where you don't want it to. Installling an LED in the headlight housing and connecting it to the PCB ought to work just fine. Depending on the headlight lens, you might want to consider putting a surface mount LED inside and keeping the lens.

Whatever you do, good luck with the project.
                                                                        -- D

[jonathan]

Ted,

I do exactly what you have suggested.  Putting the LED directly in the headlight makes a huge difference.  You can cut the plastic lens in half (carefully) to make room for the LED.  Even better is to put in an after-market lens, if you can find one.

If you check my past posts on my 2-8-0 projects, there should be some useful photos to help you with this.

I use my own 1k ohm resistor, placed in the gap between the split frame and the back of the smokebox front.  There is about a 1/4" dead space in this area. 

I have reused the stock resistor, with good results, as well.  Remember, polarity matters.

In the prototype, steam loco headlights weren't very bright.  However, I like it bright when running models.  Just looks better in my opinion.

Regards,

Jonathan

[richg]

Jonathan reminded me about the below link I had stored the first day I saw it.

http://www.bachmanntrains.com/home-usa/board/index.php/topic,22055.0.html

Everyone, store the link in Favorites. I have seen questions before about dim lights in Bachmann locos here and other forums.

You might also save the page to your PC. If the Bachmann forums ever go through a modification like they did a few years ago, this page might disappear. That way, all you have to do is click on the file you save to your PC and this page will open up as if it still existed in the Bachmann forums. I have done that with some personal MR sites that went away and I still have all the data. Sometimes people change their Photo Bucket site and their pictures disappear from the forum messages.

Take advantage of the power of your PC. You do not have to be a PC guru. Compare it to putting a large file cabinet in your back room office to store important papers.

Rich

[tmiller]

Hey guys,

A lot of good information being passed around on this thread. It is also an educational experience for me.

Here are my thoughts and concerns:

I do agree that adding an LED out in the open in the boiler unit might be a mistake, with a lot of light bouncing around inside. The only correct way is to mount it in the headlight assembly. My concern is eliminating the light pipe from the light housing. I am assuming that it is a square piece of plastic inserted and glued into the housing. The light from the LED travels up the pipe, and is diffused at a right angle through the lens.

The pictures of the 2-8-0 headlight assembly do not match what I have. That assembly is out in the open, and much easier to work with. In my situation, the light pipe is what fits through the top of the boiler shell, and lines up with the LED inside. My biggest concern is how to remove the light pipe, without damaging the headlight assembly. It would have to be drilled out, as I am sure it is glued in. It would be like working on a swiss watch. Small to minute in size. Removing the light pipe seems to be the biggest hurdle right now.


Then comes the issue of finding an LED that small. I am going to a train show this Sunday, so will seek out the LED guy to see what he has.

Now, as for the resistor, do I have to do anything with it, since it is most likely on the PCB in the tender? My guess is to simply connect it to the two wires coming from the decoder, through the engine.

Still pondering this delicate operation.

[tmiller]

Jonathan,

Just had a thought after looking at your 2-8-0 installation, which by the way, you did a great job.

Why not just leave the light pipe intact, and drill out the back of the light assembly. Then run the wires out the back, down into the boiler shell, much like you did. They would hardly show, and wouldn't look bad otherwise. That way I should be able to keep the lens intact in the front.

That sound like a game plan. What think?

Ted

[Doneldon]

Ted-

You'll need to drill out the light pipe. Either use a Dremel style tool at a low speed, for maximum control, or a pin vise which will allow you to hand drill it. Keep in mind that you don't need a perfect job as the headlight itself will cover the hole in the top of the smokebox and the bottom of the headlight fixture.

You can use a surface-mounted LED or a very small LED with legs. The smallest regular LEDs I've seen are 3 mm but I understand there are some as small as 1.88 mm. That's about .076 inch diameter. As important as the size is the color. You can find bright white, sunny white, cool white, warm white, yellow-glow white and probably others. Regular white LEDs tend to be quite blue which is unrealistic. You need to paint a little thinned yellow on those. I would use either a warm white or yellow-glow for electric headlights.
                                                                                         -- D

[tmiller]

Don,

Thanks for the reply. I am curious as to your thoughts on drilling out the light pipe, vs drilling out the back? That was my original idea, but I figured it might be a real chore. I guess the only benefit of drilling out the pipe, would be that all the wires would be hidden. And by drilling out the back, I would retain the lens up front, which may not be important.

I do need to measure the opening to see what size I need. I agree going with the yellow-white. Right now it is a yellowish tint.

Hopefully I will find a suitable LED Sunday at a local train show.

Thanks for your advise.

Ted

[Doneldon]

Ted-

Well, I think that feeding the wires through the bottom of the light housing conceals them. Yes, many electric headlights on locomotives which were built before electric headlights, and some which were updated with more powerful headlights had exposed conduit (what we call BX today) but our two wires snaking into the smoke box don't look like one BX cable which wouldn't go into the smoke box in the first place. So I think the bottom feed works best and looks best. And I think you can still use the lens even if you drill out the light pipe and bottom feed.
                                                                                                                                                          -- D