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
Life is what happens while you are making other plans!
The white wire will not have any voltage. It is the ground side for lighting.
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.
woodone The white wire will not have any voltage. It is the ground side for lighting.
RR_MelThe 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?
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 The Blue and white wires should be coming out of the MRC Decoder. Mel
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,
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
Alton Junction
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).
That will work if he wants the lights on all the time in both directions but will not give him DCC control over them.
Jay
C-415 Build: https://imageshack.com/a/tShC/1
Other builds: https://imageshack.com/my/albums
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.
If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.
Save yourself a lot of trouble, heartache, angst and grief, and go with a better [Miniatronics] 1 1/2 volt bulb.
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.
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
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.
richhotrainBob, 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
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,
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
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.
woodoneThere 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>
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!
Well, what the heck, it can't hurt as long as he adds the appropriate resistor to the SMD. Give it a try.
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.
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.
Woodone has the answer .... but apparently either nobody believes him or doesn't want to try it !
Mark.
¡ uʍop ǝpısdn sı ǝɹnʇɐuƃıs ʎɯ 'dlǝɥ
Issues like this can be confusing for those with limited electrical DCC experience. We shall see.
I would certainly try the suggestion.