# Digitrax and lights



## vette-kid (May 2, 2020)

I recently installed a digitrax sdh166 in a Bachmann DCC ready E7. I swear the lights worked at first, but I cannot get them to work anymore. I tried wiring the LED board directly to the decoder, bypassing the 8 pin plug and still no joy. I even tried wiring a separate light directly in and that won't come on either. I tried wiring the front, rear and aux light output from the decoder and none of them will like anything. The lights do work when when battery power is applied, so the lights and board are good. CV49 is set to 1, but default is 00...I can't input 00 on my system... Only 1-255?? Is this my problem somehow? Something else I can look for? 

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## mopac (Feb 24, 2011)

I would say yes. Problem is in controller. The lights have been turned off. Which is one of
the functions. Do you have DCC? If you do try F8. I think that is lights. If no DCC, see if a
train shop with a DCC layout can help. If they do help you, buy something.


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## vette-kid (May 2, 2020)

I do have DCC F8 is mute. I can't find a finding button for lights listed anywhere. I did try CV8 to 8(reset), but it didn't do anything for me. It did reset CV49, but no change in lights.

I'm tempted to just bypass the decoder see of they will run as installed... Main board feeds the LED board. Just removing the lighting wires from the decoders 8 pin should allow them to function normally as you are taking the decoder out of the equation... If I understand it correctly. Should have tried that before I de soldered the led board from the main!!

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## rickbz28 (Jan 10, 2016)

On Digitrax decoders F0 turns the lights on and off. Have you tried that yet?


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## vette-kid (May 2, 2020)

rickbz28 said:


> On Digitrax decoders F0 turns the lights on and off. Have you tried that yet?


I don't have f0, I do have FL, that I assume is the same thing. It did not have any effect.

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## vette-kid (May 2, 2020)

Good news/bad news...

I still don't know why the lights didn't work initially when connected through the 8 pin harness. Possibly it was the CV settings and/or F0 and in my haste I missed it. Lesson learned (so you would think)

When bypassing the harness and working the LED board directly to the decoder it seems the wiring is reversed. What is labeled as the + wire needs connected to the common lead from the decoder.

The good news is doing this and using FL (F0) turned the lights on.... For a millisecond.... Then the magic smoke escaped from the LED board! So it seems using this method requires a resistor, even though the board does have what appear to be small resistors built into it (labeled r1/r2). 

So the bad news is that I ruined the LED board.

More good news, everything else is fine. And Bachmann sells a replacement board with built in Mars lights... So upgrade time! I'm also going to call them to confirm whether the main board and/or led board have the required resistance or if I need to add one... No more guessing!

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## vette-kid (May 2, 2020)

Ugh, got the new board in and still struggling. The number boards and bottom light illuminate fine, no top light or Mars function. I've been reading the digitrax manual and I'm confused. It take about light functions, such as Mars lights, and programing then to come on with F1. F1 is the bell??? F0(FL) is lights off-on. So possible that the mats light works I just don't understand how to access it. These things are clearly programmed by engineers from an engineers perspective... It's confusing! The function selections in the manual do NOT correspond with the function buttons on the controller, I have no idea how to get to them though.

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## Magic (Jan 28, 2014)

Try F5 for the MARS light, in fact try all F keys you can't hurt anything.

Magic


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## vette-kid (May 2, 2020)

I have. I think it's in the wiring, the Bachmann light board has an 8 pin plug, although the F1 wire (green) is connected at pin 3. I think I have a few options, but I'm not sure yet.

One is to jumper pin 6 and 3. Any function on that pin from the Bachmann light board should then be active with the headlight. I'm assuming that the bottom light is us supposed to be the headlight and the top light is Mars only.

Two is to connect the green wire directly to the positive side of the Mars light with a resistor. I'm not real sure, but I believe I could leave the negative connected to the light board for common -. It's a tiny LED so I'm not sure how much resistance is needed, Bachmann doesn't give any details about it, I've asked, but nothing yet. So probably start with 1k resistor.

Another oddity is that there are only two wires for the supposed Mars light. I would have expected three wires and two LEDs. May just be a pulsing action on one? 

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## vette-kid (May 2, 2020)

Finally, success... Sort of. Turns out the Bachmann Mars light is a constant red light. Not too exciting. I'm not sure if that was prototypical, but it's not what I was hoping for. So I wired in a ML2. For the reflect I had to wire it with the headlight directly instead of the way it came. I then wired the ML2 to F3 (brown wire) lead bypassing the main board completely. 

So all that brings me to a few questions. First; does the PCB have anything to do with how smoothly the motor stops and starts? It's a smooth runner and I don't want to mess with how it runs. But... The ML2 and track power adapter make it rather crowded in there. If I can do away with the Bachmann PCB I'd feel a little better about it. I was getting a few shorts due to the board compressing a bit with the shell on. 

Second; why do they give you accessory functions that are already tied to another function? Example: F1 controls the bell, so anything you attach to the F1 wire will activate with the bell... Annoying. F3 also had a sound, I'm not sure what it is, but it only sounds once and but continuous. So I'm ok with it for now. But why do it this way? Why not give those wires a dedicated F key? It is there a way to reprogram that?



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