# DCC HO scale Locomotive Runaway!!!!!



## SF Gal (11 mo ago)

Have you ever experienced a runaway locomotive while running DCC?
Happens to only one of my locomotives.
*The scenerio:*
I have 8 DCC locomotives of different manufacturers and decoders, *"ON LINE"* ....all addressed per their road numbers.
Five locomotives were sitting in the yard or on sidings, awaitng commands from my NCE ProCab, and one of those on the siding, is a new Altas SD45 (#970)with Loksound, my only Atlas, my only sound locomotive.
This new sound locomotive runs like a champ and sounds wonderful! No complaints.
I was running 3 non sound locomotives on the layout and a passenger car on one consist derailed at a turnout and caused my power supply to detect a momentary short. For a very brief instant, I lost power ....for a instant.
The MRC tech transformer detect, reset power before the flywheels stopped and in that same instant my Atlas engine with Loksound illumated its forward lights and roared to life full speed forward with no sound, on the siding.
The panic button was my life savour.
So, I ran one locomotive on the track again and briefly shorted the main power again, and again, the Atlas roared to life with no commands to do so. I can do this all the time if I want.
No other locomotive or decoder does this!
So I was wondering if any of you EVER experienced this with any of your locomotives?
For now, *if* I am not running the Altas locomotive, on the main or in the yard, I park it on a dead siding that I purposely removed power to.









Now, I never did a test to see if the locomotive was on the main running with a command and the track power shorted. I think the packet would keep broadcasting command speed when power continued, but not sure. But it is a future test to do.


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## MichaelE (Mar 7, 2018)

Have you turned off DC in the Loksound decoder?


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## mesenteria (Oct 29, 2015)

Try writing 34 to CV 29. If you want long hood forward or some other unusual configuration of lights or whatever, google 'CV29 calculator' and just look down the list of options. Find the one that fits, enter that into CV29. The value 34 works for addresses above 127, but for you it prevents DC compatibility and renders the decoder only able to respond to DCC rail power.


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## SF Gal (11 mo ago)

Okay, my good members, not a big fan of changing CV values but I will give it a shot as I do know how to read and write CV values, understanding how to make a value from bits is kind of over my head.
So, I googles "disable DC on a Atlas Loksound decoder".
Found the ESU User Manual for Loksound V3...not sure what version of Loksound I have.
on page 29 I found the table....









So I am figuring bit 2 should be changed from a 4 to a 0.
The current value, inside my locomotive with Loksound, for CV 29 =42 So....how is it, this values default is 42 and what value do I need to change CV29 to, in order to disable analogue DC operation?


mesenteria said:


> Try writing 34 to CV 29. If you want long hood forward or some other unusual configuration of lights or whatever, google 'CV29 calculator' and just look down the list of options. Find the one that fits, enter that into CV29. The value 34 works for addresses above 127, but for you it prevents DC compatibility and renders the decoder only able to respond to DCC rail power.


Guess I should of read and comprehended your post before I wrote the above,
Thanks I will try CV 29 and write 34 to it. Wondering why I am seeing value 42 as a default in CV 29? With railcom enabled and DC disabled is the only way default can be 42. I think if I write 34, it should work....Thanks for the CV29 calculator link, it rocks!!!!


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## Lemonhawk (Sep 24, 2013)

42 (Or the answer to the* Ultimate Question of Life, the Universe, and Everything) set in CV29 (42 or 00101010) indicates that bit 0 is 0 for normal direction, bit 1 is 1 for speed steps 28 or 128, bit 2 is 0 meaning analog operation is off, bit 3 is not use and bit 4 is 0 for speed curve thru CV 2,5,6 and bit 5 is 1 meaning the loco uses long addresses. If 42 is the setting then analog operation is turn off, so that is not the reason the loco takes off *


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## SF Gal (11 mo ago)

So confusing! How do you change numerial to binary?
Anyway I see you read binary from right to left, so f'ed up..._giggle_
So I should leave it at 42...UG!
I might try 32 and turn off railcom(bit3)...guess I better read up on railcom and what it does for NCE Procab. UG...looks like the sound card uses railcom to change sound in keeping with speed.
Still not messing with CV 29. I am leaving it at 42 and keeping it on a unpowered siding till I find a answer .


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## Lemonhawk (Sep 24, 2013)

I would leave it, I think something else is causing this. Might we worth an email to the decoder manufacture. Shutting analog off would have been my first guess, but that's not it. You can find a calculators on the internet that will convert the binary 1's and 0's number to decimal. or just use JMRI decoder pro and it makes it much easier to do any of this if binary, octal or hexadecimal is not your choice of base numbers. 
I use the windows and Android Free42 app, but this calculator will just add more confusion as its a reverse polish notation (RPN) calculator - has no = or () on the keyboard.


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## Conductorkev (Nov 5, 2021)

SF Gal said:


> So confusing! How do you change numerial to binary?
> Anyway I see you read binary from right to left, so f'ed up..._giggle_
> So I should leave it at 42...UG!
> I might try 32 and turn off railcom(bit3)...guess I better read up on railcom and what it does for NCE Procab. UG...looks like the sound card uses railcom to change sound in keeping with speed.
> Still not messing with CV 29. I am leaving it at 42 and keeping it on a unpowered siding till I find a answer .



Binary takes some getting used to.

Far right is 1. So from right to left you times by 2. If there is a 0 you don't count it. If there is a 1 you add whatever number that represents that spot.

Hard to explain without showing you a chart.










There ya go.

So there is a 1 where 128 is

Next 1 is where 64 is
So add 128 and 64
192
Next is 4
196
Next 2
198
Then 1 

199

Basically you break lines to 8 bits and use that chart to get the number.

If you need to change numerical to binary well just reverse course.

Say you want 50

You go like this

Can 128 fit in 50
No so you put zero

Can 64 nope so the second number is zero

32 yep do you put a 1 minus the 32 from the 50 which leaves 18
So 16 would fit into that

Leaves 2 because we minus the 16 from 18. We know 2 is the second to last so the answer is

00110010


Hope that helps. Gosh i jusr used brain cells that I've not used for a long time lol.


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## mesenteria (Oct 29, 2015)

You have nothing to lose from learning the many options in the table that accompanies all decent CV calculators for CV29, selecting the one that fits best for you, and then trialing that setting to see if your unwanted behaviour goes away....reliably. Over at MR forums, the DCC guru, the late Randy Rinker (electronics engineer), always advised setting CV29 to a value of 34 for most cases. Those petitioning for help never came back to say the advice was a bust, at least not to my recollection.


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## J.Albert1949 (Feb 3, 2018)

I've had this same problem, seems it can be common with Digitrax decoders.

*SOLUTION:*
Install Java and JMRI.

Then, create a roster entry for the problem engine
Go to the "Basic" panel and pay attention to the last item.
Set it for "Digital only" (or something similar to that).
This TURNS OFF the decoder's response to DC.


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