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?
you can use the red track power wire to power your LED, but you must use a resistor. I would use a 1K resistor from the right rail ( red wire) to the positive side of the LED. Then the white- yellow? wire for the grounding .
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.
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.
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?
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.
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,
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.
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).
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.
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.
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
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.
