# Why did DCS steam engine startup?



## Smokinjoe52 (Nov 8, 2013)

I added LED lighting to my wood sided passenger car that is on display with my MTH PS3 Steam Engine. The steam engine is on a couple pieces of track with the passenger car. I decided that I wanted to light the passenger car while on display, so I connected a 12v AC 1000MA supply to the tracks. The first time I powered up, the steamer fired up after a few seconds. It did not move, just went through the power-up sequence. I run the locomotive in Command mode, so can't understand why that happened since it did not get a DCS command. So I pulled the tracks apart between the passenger car and the steamer, but can't understand why that would happen.

Anybody have an answer to this one?

Thanks,

Joe


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## mesenteria (Oct 29, 2015)

Is that a dual mode decoder? Can the locomotive be run on DC current (I think MTH locos can, just like DCC locomotives). 

DCC decoders can be made insensitive to DC current if it is offered them on the rails. CV29 must be set to a value of 34. A value of 38 restores the decoder's sensitivity to DC current and it will 'light up' if sufficient voltage is applied to the rails.

You'll need to consult your DCS manual and see if there's a similar feature.


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## Smokinjoe52 (Nov 8, 2013)

I am using AC to light the passenger car. That is why it is perplexing.


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## Suncat2000 (Oct 23, 2016)

Smokinjoe52 said:


> I am using AC to light the passenger car. That is why it is perplexing.


Use DC power or a DCC signal. I think your decoder isn't liking the variable voltage of the AC power. A DCC signal switches polarity at specific frequencies and doesn't alter the voltage, so it probably isn't getting what it needs to operate properly. 

Sent from my SM-G930V using Tapatalk


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## Lehigh74 (Sep 25, 2015)

I don’t have an answer, but I can tell you that it’s not a unique problem. I have a few (PS2) engines that sometimes start up and then move after a few seconds when power is supplied. For some reason, they don’t always see the watchdog signal even though they are right next to engines that stay dark and silent when the power is supplied.


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## gunrunnerjohn (Nov 10, 2010)

The answer is surprisingly simple. If you power up a PS2/3 locomotive and it doesn't see a watchdog signal in the first few seconds, it comes up in conventional mode. That means that the lights, sound, and smoke if it has it, are enabled. If you briefly interrupt the power, it'll take off on your little track, so it's probably not a useful way to display it.


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## Smokinjoe52 (Nov 8, 2013)

Thanks John,

I removed power from the locomotive, and all is well. I don't think I ever knew about the watchdog signal and reverting to conventional.

Joe


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## gunrunnerjohn (Nov 10, 2010)

Probably removing power is a good plan. 

Both MTH DCS and Lionel TMCC/Legacy will run in conventional if there is no command signal present, nature of the beast.


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