I just installed a Digitrax SDH164Ddecoder into a HO Mehano Thalys locomotive. Everything worked perfectly I even programmed a new address with my Digitrax DT402D throttle. All of a sudden the light function does not turn the light off anymore. I reset the CV to factory defaults and the light still does not turn off. What happened? I've been having issues with the other Digitrax SDH154D decoders that I RMAed.
Well, that's an odd one. When you reset the decoder, did the address go back to 3? Does everything else work properly on address 3?
My first guess would be a loose wire, or perhaps you used shrink-tube insulation and it slipped, exposing a wire joint which is making contact with the frame or other metal part. It's possible that the decoder failed or shorted, but usually the light would stay off when that happens.
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Hi,
I may have misunderstood your posting - but from what I gather it sounds like the bulb burnt out. It could be the need for an LED as the electronics won't handle the light bulb - or the bulb overheated and burnt out.
I'm not an expert on this, but I suspect that is the problem.
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Mobilman44
Living in southeast Texas, formerly modeling the "postwar" Santa Fe and Illinois Central
Have you tried to research and troubleshoot the problem? I went to Digitrax web site and in the user/installation manuals (which you should have), I found the following:
"Strange" locomotive light operation" - If you can't control the operation of the lights in your locomotive with your throttle (in default 128, or 28 speed step mode), be sure that the decoder is programmed for advanced 28 speed step mode. Your Digitrax decoder was shipped programmed to 128 speed step mode. You may have changed your decoder's programming when performing the decoder test procedure. In any case, if you are not able to turn the locomotives lights on and off, you will need to change CV 29 to 006/x06 to have proper light operation when using your Digitrax system in its optimum 128 speed step mode. Do this by programming CV29 with a value of 006/x06"
"If you can't turn the lights on and off or the lights blink when you run the loco, this is symptomatic of a Standard (14 speed step operation) decoder trying to process 28 speed step Advanced packets" - Be sure that the decoder and command station are using the same mode by reprogramming the decoder or by changing the command station's operating mode.
Don't know if this is your loco's light problem, but it's a start.
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Mehano steam engines had the light wires connected to pickups on the front set of drivers separately from the pickup for the motor. Perhaps the Talys is wired the same. Did the headlight ever work correctly with the decoder? If so, the current draw of the headlight bulb may have overloaded and burned out the decoder's function circuitry.
Is this the forward head lamp connected to the white wire that is the problem?
What is the lamp? Bulb, LED?
Any resistors installed in the circuit?
I assume this was a hard wire solder installation?
If this was the factory installed bulb connected directly to the decoder without any protective resistor, then there is a good chance that the function output is damaged. I have personally not seen one fry with the lamp permanently on, but perhaps that is what has happened?
See this link for some reference material http://www.tonystrains.com/technews/install-lamps-decoders.htm
With the SDH164 you have several functions, so if you are not using them all, you can rewire your lamp correctly to a different output lead and remap the function to F0
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Yes it went back to 3. Everything else worked properly.
The headlight did work correctly in the beginning.
The forward light is connected to the blue and white wire. The lamp is an LED. The lamp is a prewired 12V.
I think I will switch to the Digitrax DH165A0 or Soundtrax and TCS decoders.
Sounds liek you are getting into troubel with these "12v LEDs". Next time try an regualr LED and a 1K resistor, don;t depend on ayone else's having done soemthign correctly. Several things could have happened here, however if the light never turns off anymore, that's almost a sure sign that the function ahs blown out. That's goign to happen in one of two cases, first, the pre-wired 12V LED draws too much current, or second, there was a short in the wiring. SInce the light initially worked, I'm leaning towards the first option, however if there were any bare wires and one touched somethign like a track pickup or motor output, it could also blow the function lead, and this might not have happened until the loco was run for some time, as the wires shifted or even worse, got caught in the moving parts.
--Randy
Modeling the Reading Railroad in the 1950's
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I think the problem is that so-called "12 Volt LED." I've seen some of them advertised that draw more current than an incandescent bulb.