Out of curiosity...

... why do you think putting a GoW bulb with a resistor in the headlight will be any easier than putting an LED with a resistor in? You know you can buy tiny LEDs with wires already soldered to them on Amazon, for example, in packs of 10. and you'll probably have to keep doing it with a GoW bulb. They burn out a lot faster.

Why a GOW bulb

The loco is painted and the GOW is glued in.  The wires are long enough so that all i would have to do is add the resistor  I have used 0603 LED for markers and back up lights on F7 diesels that I soldered the wires on myself.  So using leds is not a problem, but I don't want to mess up the brass smokebox front and the headlight castings as well as the paint job. The loco has a new can motor that was just put in.  If the resistor is not workable, then a 0402 led with a reflector would be the answer.  The resistor would also increase the life of the bulb..

Bill

what voltage?

What voltage does the info with your decoder say it puts to the lamp to give 100ma max? This is needed to calculate resistance needed.

DrJolS

Voltage of Functions

The data with the decoder indicates that the functions are designed for 12-16 volt, 30-40 ma incandescent lamps.  I have not measured the voltage between the white and blue wires as of now.  That will be a job for tomorrow.  The data sheet for a Digitrax DH123D suggests a 22 ohm 1/4 watt resistor in series with a 12-16 volt  bulb with a FX3 function rated at 500ma,  I assume that this was to control the in-rush current..

Bill

Since you are in the planning stages, may I recommend

that you look at a Decoder Buddy Mini?  It might fit nicely and was made with such installations in mind.  When Dr. Jol calculates the resistance you can order the DB from me and I’ll include in the resistor.  The decoder Buddy Mini and a https://www.ncedcc.com/online-store/D16MTC-21-Pin-decoder-fits-most-new-Athearn-Locos-p78626867 or any other 21-pin decoder will fit into the locomotive easily,  make the wiring a lot neater and leave you some speaker output and stay alive pads if you decide to use them in the future.  http://www.nixtrainz.com  They aren’t at the dealers yet!

Yes, the next run will say Mini..... and the A0r is labeled correctly on the instructions!  Works well I spite of what it says......

Nick

Short answer - probably YES

More reliable than a calculation:

I got in touch with my club's electronics guru, who is more acquainted with NCE products. He is also more of a magician in extracting info from web pages, which I needed because I can't figure out how to find NCE's manuals for specific decoders. Results:

Manual for D13W doesn't mention adding a resistor to the GOW's circuit.

per  NCE and Tonys Trains, D13W is a smaller replacement for D13SR.

per MarkGuru, the manual for D13SR for lamps with current between 50 and 100 milliamps says.we recommend a 22 ohm 1/4 Watt series resistor in function leads with each bulb (this will also greatly extend bulb life).”

I hope this will do it for you.

DrJolS

Bulbs vs LEDs

OK, OK I try to put in a LED

You win!!.  I'll see about the LED.  Any ideas on a safe way to remove the bulb that is glued in?  Also if an EE is on line and available, I would like to know if the resistor will reduce the in-rush current.  My Physical Chemistry background is much help with electronic stuff. 

Bill

Glued in bulb...

Any idea what KIND of glue it is?

Could be hot glue, epoxy, ACC, Elmers.... what color is it?  Yellowish, milky, clear?

If you can

carefully with a long metal awl or something similar only break the back end of the glass bulb.  Now, if you’re lucky, your lens issue is solved.  Next take some Microcrystal clear or Formula 560 canopy glue on the end of a toothpick and fill the remaining glass light bulb case with the glue.  The toothpick is a major tool for this process.  Let the glue dry and add a little more to slightly overfill the glass and surrounding hole.  Use a pre-wired 0603 smd LED and set it in the slightly over filled puddle so it is square and stable.  Let the glue dry again.  Test the LED.  If it works paint the whole area with black paint so no light leaks out.

I use this procedure all the time now and usually make the convex meniscus lens for the front the same way.  If the bulb cracks or breaks in front use an implement of destruction to the remove rest of the glass and use the clear glue to make the lens in situ if necessary.  The glue will build seamlessly in layers and form a good meniscus.  It the lens looks weird then cut it off with a sharp blade and try again.

If you need a single or two LEDs shout to me and if you want some pictures of the process do the same.

Nick

Postpone your time to deal with LED?

Look at the last line of JoeF's post. You don't really need to do the LED until after the GOW burns out. How long will that be? With the resistor in its circuit its lifetime will be longer than without it.

No burn -in high current to start an LED.

DrJolS

It now has a led headlight and sound

The Old PFM light Mike now has a 0603 led for the headlight and a lens that I got from Mouser Electronics several years ago.  The NCE decoder (non sound) was replace with a an Soundtraxx Econami decoder.  An Iphone 4 speaker was placed in the boiler between the boiler weight and the can motor and it fit easily.  The sound is coming from the engine and not the tender as it should. Now for some weathering.

Bill 

Hey Bill,

looks great!  
 

Nick

Decoder buddy

Nick,

I did use a decoder buddy in the tender to mount the 21 pin Econami decoder.  It worked very well and I would recommend it.  The ebay dealer "modelrrsupply"  suggested it and several other options and they were very helpful. I have not seen any adds on the mini as yet.  With the speaker in the boiler, there was plenty of room in the tender.  The part of my layout in the picture dates back to the late1960's and the bare tree trunks are the result of the licken crumbling away.  They will be fitted with ground foam leaves soon. First things first!

Everybody else, thanks for the suggestions and replies.  I appreciate all of the input 

Bill

Hi Bill,

Thanks for the reply!  I’m glad the Decoder Buddy, the Economi and the LED worked out for you!  Enjoy!

Nick