Athearn Genesis 1.5 volt bulb replacement with LED.

[richhotrain]

woodone

Rich, you posted a wiring diagram of an MRC decoder earier.  

That was richg1998

Rich

[woodone]

Rich, you posted a wiring diagram of an MRC decoder earier. If you look the way they show how to hook up the lights you will not that both lights show a common, THAT IS THE POWER TERMINAL. The other wires ( one to each bulb) is the control wire. The LED does not care where it get its power, but it must be enough ( about 3 volts) to make the LED light. With getting power from the rail you will be getting 1/2 wave form from the rail. If you read the voltage across both rails you should see about 14 volts. so 1/2 that is about 6 volts. YOU MUST USE A RESISTOR !!! 1K will work. you can use more if you want to dim it a bit.

[richhotrain]

richg1998

Issues like this can be confusing for those with limited electrical DCC experience. We shall see.

I would certainly try the suggestion.

Rich

 

I, for one, fall into that category.  Once the OP solves his problem, and assuming that he reports back that the rail power suggestion worked, I hope that someone more knowledgeable than me will take the time to explain this in more detail.

I always thought that the wiring of loco lamps, headlight, rear light, ditch lights, were always dependent upon their assigned function outputs.  For one thing, the function output voltage is typically lower than the track voltage, or so I thought.  And, I always thought that using the correct function output tab was critical to the proper application of CV values for advanced performance of the lamps.

So, do you not even need to use the function output tabs as long as the other leg of the LED or incandescent is wired to the accompanying common tab for the designated function output tab?

Anxious to learn more about this whole topic, and anxious to hear if the woodone solution indeed works.

Rich

[richg1998]

Issues like this can be confusing for those with limited electrical DCC experience. We shall see.

I would certainly try the suggestion.

Rich

[Mark R.]

Woodone has the answer .... but apparently either nobody believes him or doesn't want to try it ! 

Mark.

[richg1998]

I found the PDF quite easily but I don't think it will be much help. The decoder must have a dedicated 1.5 volt regulator.

http://www.modelrectifier.com/resources/dcc/0001821%20diesel%20Athearn%20F%27s.pdf

 

The 12 volts DC is easy to find. Right at the output of the full wave bridge rectifier. Just no control of the lights if you go that way.

Rich

[farrellaa]

I tested the voltage on the light socket at the board and it is 1.55 volts. The socket has four pins but only two are installed in the plug; the outside ones the get the 1.55 volts. The inner ones read about 5.6 to 6.0 volts. I couldn't seem to find any other points on the board to connect to? I never found a 12 volt reading at any of the connection points. I will try this method suggested by woodone and see what happens. I do want to maintain function control of the lights. Also may call Athearn and see if anyone there has a solution.

   -Bob

[richhotrain]

Well, what the heck, it can't hurt as long as he adds the appropriate resistor to the SMD.  Give it a try.

Rich

[woodone]

The control comes from the negitave side not the power side.

The function wire completes the curcit.

Trust me, I have done many just like I said.

They work just fine!

[richhotrain]

woodone

There are only two wires going to the LED. One is the positive, the other is the ground. Find the positive wire, cut it and run a wire from the LED.to the Right rail wire and use a resistor (1K) between the LED and the right rail. Now it will be bright and you can control it>

 

If he bypasses the function output for the headlight by tapping into the rail pickup, how can he control the headlight (e.g., off in reverse, dim under Rule 17, etc.)?

Rich

[woodone]

I have given the OP the quick and easy way to get this working. He will have control of the H/L just like I have stated. Taping the right rail will give you 1/2 wave A/C volts and the control wire is still on the original board. Try it! It works!!!! The installer of over 1000 installs.

[richhotrain]

farrellaa

As to your questions: It is a full featured sound/motor/light decoder with no other boards. The photos I posted show that it is a self contained board similar to other Atlas/Athearn style but without the two rectangular slots for mounting.

The light output for the headlight is a socket/jack on the pc board with a plug-in light wire harness. I replaced this (incandescent bulb) with a SMD which as I explained doesn't work as there are only 1.5 volts available from the decoder socket.

I will check the actual voltage today with my multimeter, but am sure it is around 1.5 volts. I also may (if I can get enought time today) trace the circut for a 12 volt output that I can tap into (as was mention by one of the other posted comments), which is what I was originally looking for.

Bob, call Athearn Customer Support and tell them the problem.  If the function output supply is only 1.5 volts, they can suggest a workaround since an SMD needs to be resistored on a 12 volt power supply to work.  You want to use the function output, not track power, so you can control the lighting effects.

Rich

[woodone]

There are only two wires going to the LED. One is the positive, the other is the ground. Find the positive wire, cut it and run a wire from the LED.to the Right rail wire and use a resistor (1K) between the LED and the right rail. Now it will be bright and you can control it>

[richg1998]

This fellow has tons of useful info on DCC. Keep the link.

Info on light bulbs and LED's.

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

Rich

[farrellaa]

richhotrain

Bob, sorry if my 'what's all the fuss' comment appeared to be directed at you. I was referring to all of the discussion about different colored wires, et.al. Let's go back to basics. Is the MRC decoder strictly a sound decoder without light functions? Is there a separate Genesis PC board where the 1.5 volt incandescent is connected? I do agree with the comment that you need a multimeter to find out the voltage on the function output tab. As you know, trying to power a SMD off a 1.5 volt power source is not going to work. Rich

Rich,

Sorry if I misunderstood your comments. I am getting a little frustrated with this issue.

As to your questions: It is a full featured sound/motor/light decoder with no other boards. The photos I posted show that it is a self contained board similar to other Atlas/Athearn style but without the two rectangular slots for mounting.

The light output for the headlight is a socket/jack on the pc board with a plug-in light wire harness. I replaced this (incandescent bulb) with a SMD which as I explained doesn't work as there are only 1.5 volts available from the decoder socket.

I will check the actual voltage today with my multimeter, but am sure it is around 1.5 volts. I also may (if I can get enought time today) trace the circut for a 12 volt output that I can tap into (as was mention by one of the other posted comments), which is what I was originally looking for.

I appreciate all the suggestions given you and the others. I will keep you posted on my findings and see where all this finally leads me to.

Thanks,

   -Bob

[richhotrain]

farrellaa

 

 

richhotrain

The Athearn Genesis incandescent bulbs are 1.5 volt bulbs, and they are crappy.

The 2-wire bulb is simply replaced with an LED with appropriate resistor attached on one of the two wires.

What is all the fuss about this?

I have several Athearn Genesis F3 and F7 locos, and i have replaced burned out incandescents with resistored LEDs on all of them.

Rich

 

 

 

 

Rich,

I would agree with you on the non-sound Genesis, as I have done on my others with SMDs mounted to fiber optic rods. If you read my comments in the previous posts, I have done exactly what you are saying, which is why I did it myself, but it doesn't work because the output from the decoder to the headlight is 1.5 volts; not enough to power an LED? This is what all the fuss is about.

I have installed LED's, sound systems and standard decoders in Big Boys, Challengers and most other diesels and steam locos, so this is no big deal for me, just not working because of the obvious; not enough voltage. What I have been asking for is help in bypassing the 1.5 volt light plug and finding 12 volts so I can install an LED. Or, as was suggested and what I am coming to the same conclusion myself, install another incandescent 1.5 volt (maybe Miniatronics this time).

  -Bob

 

Bob, sorry if my 'what's all the fuss' comment appeared to be directed at you.  I was referring to all of the discussion about different colored wires, et.al.

Let's go back to basics.  Is the MRC decoder strictly a sound decoder without light functions?   Is there a separate Genesis PC board where the 1.5 volt incandescent is connected?

I do agree with the comment that you need a multimeter to find out the voltage on the function output tab.  As you know, trying to power a SMD off a 1.5 volt power source is not going to work.

Rich

[richg1998]

I have used the Miniatronics 1.2mm, 1.5 volt bulbs and they work just fine. Some think a real light bulb looks better than an LED.

Rich

[hobo9941]

Save yourself a lot of trouble, heartache, angst and grief, and go with a better [Miniatronics] 1 1/2 volt bulb.

[richg1998]

farrellaa

I know this subject comes up often but I have not been able to find a solution to my problem. Did search on this forum and Googled it. I have an older Genesis F3?7 with the MRC sound decoder. The SMD I installed to replace the 1.5 v incandescent bulb requires at least 3 volts so it barely glows. How do I connect the LED with or without resistor to the decoder? The current headlight connection is with a plug in at the end of the board. Is there a resistor built into the pc board that can be bypassed or am I stuck with using the 1.5 v incandescents?

   -Bob

 

Get your multimeter out and an Optivisor, magnifying lens. Look for the four diodes that form the full wave bridge rectifier where the DCC connects. Follow the traces as there may be a another diode nearby. Some decoders are like that. The output of the bridge will be filtered 12w vdc as those leads connect to a large square capacitor nearby. Check with your meter.

Rich

[modelmaker51]

That will work if he wants the lights on all the time in both directions but will not give him DCC control over them.

[woodone]

find the right rail pickup wire ,even you should be able to trace the wires coming from the trucks to the board. Solder a wire to this termanial and add a 1k resistor run this to the LED and be done.

[farrellaa]

richhotrain

The Athearn Genesis incandescent bulbs are 1.5 volt bulbs, and they are crappy.

The 2-wire bulb is simply replaced with an LED with appropriate resistor attached on one of the two wires.

What is all the fuss about this?

I have several Athearn Genesis F3 and F7 locos, and i have replaced burned out incandescents with resistored LEDs on all of them.

Rich

 

Rich,

I would agree with you on the non-sound Genesis, as I have done on my others with SMDs mounted to fiber optic rods. If you read my comments in the previous posts, I have done exactly what you are saying, which is why I did it myself, but it doesn't work because the output from the decoder to the headlight is 1.5 volts; not enough to power an LED? This is what all the fuss is about.

I have installed LED's, sound systems and standard decoders in Big Boys, Challengers and most other diesels and steam locos, so this is no big deal for me, just not working because of the obvious; not enough voltage. What I have been asking for is help in bypassing the 1.5 volt light plug and finding 12 volts so I can install an LED. Or, as was suggested and what I am coming to the same conclusion myself, install another incandescent 1.5 volt (maybe Miniatronics this time).

  -Bob

[richhotrain]

The Athearn Genesis incandescent bulbs are 1.5 volt bulbs, and they are crappy.

The 2-wire bulb is simply replaced with an LED with appropriate resistor attached on one of the two wires.

What is all the fuss about this?

I have several Athearn Genesis F3 and F7 locos, and i have replaced burned out incandescents with resistored LEDs on all of them.

Rich

[RR_Mel]

 

As they say a picture is worth a thousand words!  The word is, use an incandescent bulb.  Wow! I’m an old Blue Box guy myself and use eight pin plug-in decoders.  I’m a long time techie and your LED conversion from the decoder doesn’t look doable to me with out experienced help.

 

My Google Search didn’t turn up anything that looked like your pictures.

 

Mel

 

 

Modeling the SP in HO scale since 1951

 

My Model Railroad   

http://melvineperry.blogspot.com/

 

Bakersfield, California

[farrellaa]

I took some photos to help clarify what I am dealing with. The red wire going nowhere is an antenna for the DC sound remote. The headlight wire assembly has an SMD without resistor, which glows but doesn't light. Any suggestions would be really appreciated. Thanks,

   -Bob

[RR_Mel]

farrellaa

 

 

RR_Mel

The Blue and white wires should be coming out of the MRC Decoder. Mel

 

 

I don't think everyone understands that this is an Athearn Genesis with a factory (MRC supplied) sound system and there are no blue, white, yellow wires. Even the speaker has red and black wires going thru a plug to the pc board. It is a self contained system which is why I was asking if there is a way to bypass the plug for the headlight; it is not putting out enough voltage to light a standard LED or SMD.

I don't know about using the track pickup wires (which are all black?) as it would need to be DC for the LED?

   -Bob

 

 

I did a Google search for an Athearn F3 Genesis circuit board diagram and found a PDF but I couldn’t get it to open.  Athearn might have a 1.5 volt regular on the circuit board that drives the headlight.  Bypassing that would get you in business.

 

If you use track power you will lose DCC control of the headlight.

 

Do you have a voltmeter to check voltages on the circuit board?

 

 

Mel

 

 

Modeling the SP in HO scale since 1951

 

My Model Railroad   

http://melvineperry.blogspot.com/

 

Bakersfield, California

[farrellaa]

RR_Mel

The Blue and white wires should be coming out of the MRC Decoder. Mel

I don't think everyone understands that this is an Athearn Genesis with a factory (MRC supplied) sound system and there are no blue, white, yellow wires. Even the speaker has red and black wires going thru a plug to the pc board. It is a self contained system which is why I was asking if there is a way to bypass the plug for the headlight; it is not putting out enough voltage to light a standard LED or SMD.

I don't know about using the track pickup wires (which are all black?) as it would need to be DC for the LED?

   -Bob

[RR_Mel]

woodone

The white wire will not have any voltage. It is the ground side for lighting.

 

Excuse me for my error!  The voltage for the headlight is on the blue and white wires, there will be enough voltage between the blue and white wires to operate an LED, as you’re using a MRC decoder you will need a resistor in series with the LED.  You can size the resistor for how bright you want your headlight. I normally use a 1.5K for my warm white LEDs and 1K for bright white LEDs.

 

The Blue and white wires should be coming out of the MRC Decoder.

 

Mel

 

 

Modeling the SP in HO scale since 1951

 

My Model Railroad   

http://melvineperry.blogspot.com/

 

Bakersfield, California

[farrellaa]

RR_Mel

The white wire from the decoder will have enough voltage to operate an LED with a 1K resistor in series.

 

 

Mel

 

 

Modeling the SP in HO scale since 1951

 

My Model Railroad   

http://melvineperry.blogspot.com/

 

Bakersfield, California

 

There is no white wire. The wires to the headlight are red and black and I have tried an LED both with and without a resistor. The resistor is 1K and I got no light whatsoever; without a resistor the LED (SMD) glows but is not bright enough to see through the headlight lens. I am assuming the output is around 1.5 volts, just enough to light the incandescent bulb.

   -Bob

[woodone]

The white wire will not have any voltage. It is the ground side for lighting.