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Unable to Read CVs

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  • Member since
    December 2012
  • From: Mesa, AZ
  • 1,530 posts
Unable to Read CVs
Posted by RideOnRoad on Tuesday, October 21, 2014 4:09 PM

I went to run my relatively newly-enabled DCC locomotive and nothing. I can turn the light on and off, but there is no movement at all. I put the locomotive on the programming track and tried to read its address and my Zephyr comes back with a "d nr". (The same result if I try to read other CVs.) I know the programming track is working because I can read the address from my other locomotive. Is there a problem with my less-than-one-month-old TCS decoder, or is the problem with the operator?

Richard

  • Member since
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  • From: Sierra Vista, Arizona
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Posted by cacole on Tuesday, October 21, 2014 4:14 PM

Have you tried address 03?  That's the default address of all new decoders.  If you have tried to reprogram the decoder from default to a long address, have you programmed CV29 to tell the decoder that you're now using a long address?

More information about your installation and programming of the decoder needs to be provided.

 

  • Member since
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  • From: Mount Vernon WA
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Posted by skagitrailbird on Tuesday, October 21, 2014 4:16 PM

Have you tried re-setting the decoder to factory defaults?  If not, I would try that.  Not knowing which TCS decoderyou are working with I cannot tell you the re-set command but it will be in the decoder documentation.

If that doesn't work, do a follow up posting with the decoder model and loco info and perhaps more help will be on the way.

Good luck!

Roger Johnson
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  • From: Mesa, AZ
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Posted by RideOnRoad on Tuesday, October 21, 2014 4:58 PM

First, let me say I am fairly new to this whole DCC thing, having converted about a month ago. I am still a bit overwhelmed with the whole thing.

The decoder is a TCS K0D8-B installed in an N-scale Kato F3A. It has been working like a champ until today. As far as resetting the decoder to factory defaults, I can't seem to make that happen. As I understand the Zephyr manual I need to read the current value, then enter the new value ("2" into CV08). Unfortunately, I can't read the value. The following are the steps I am taking:

  1. Pressing "Programming Mode", display responds with "dir"
  2. Pressing "CV", display responds with "t003"
  3. Entering "8" and pressing "CV-RD", display responds with flashing "d nr"

Same thing if I try to read the address:

  1. Press "Programming Mode", display responds with "dir"
  2. Press "Loco", display responds with "Ad4"
  3. Press "CV-RD", display responds with flashing "d nr"

The Zephyr documentation says the "D nr" means it was not able to read the decoder. As I mentioned, I know the programming track is working in that if I put my other locomotive on the track, following the same steps above I can the correctly read values in the display.

Richard

  • Member since
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Posted by maxman on Tuesday, October 21, 2014 5:04 PM

cacole
Have you tried address 03? That's the default address of all new decoders.

 

I think it is better to say that the default address is 3, not 03.  He didn't say which DCC system he has, but if it happens to be NCE then 3 and 03 are two different addresses.

  • Member since
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  • From: Mesa, AZ
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Posted by RideOnRoad on Tuesday, October 21, 2014 5:10 PM

maxman

. . .He didn't say which DCC system he has. ..

Digitrax Zephyr

Richard

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  • From: Westchester NY
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Posted by retsignalmtr on Tuesday, October 21, 2014 5:17 PM

With most decoders setting CV008 to 008 should restore the decoder to factory defaults, including the 03 address. I've had to do that a couple of times myself. If the lights are working with the programmed address I would suspect the motors contact tabs are not making good contact with the the underside of the decoder. Check for a loose decoder board in the loco. I use a digitrax system too, but not the Zephyr.

  • Member since
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  • From: Mount Vernon WA
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Posted by skagitrailbird on Tuesday, October 21, 2014 5:54 PM

The online manual for the decoder in question is to enter the value of 2 in CV 8.  I am not familiar with Digitrax systems so I can't help with programming instructions.  If you don't know how to change CV values you will need to check your Digitrax manual unless, of course, aomeone knowlegeable with Digitrax chimes in.

Roger Johnson
  • Member since
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  • From: Mesa, AZ
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Posted by RideOnRoad on Tuesday, October 21, 2014 6:14 PM

I do know how to change values. I have previously changed the addresses on both locomotives, as well as the acceleration and deceleration values. As I mentioned, everything was working just fine until today. In as much as everything continues to work with the other locomotive, and the error code indicates an inability to read the value from the decoder, I am leaning towards a failed decoder. Before I tear everything apart and unsolder (which worries me greatly) the connections, I am hoping I am missing something simple.

Richard

  • Member since
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  • From: City of Québec,Canada
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Posted by Jacktal on Tuesday, October 21, 2014 7:36 PM

If it was mine,I'd remove the shell and check motor connections...some decoder won't do most anything if they can't "see" a motor in the circuit.May be a connection has failed...just a guess....

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Posted by rrinker on Tuesday, October 21, 2014 8:12 PM

 N scale immediately set off the warning bells - most likely the decoder is not making proper contact with the motor tabs. Common issue with N scale board repalcement decoders, especially as the size of the 'slots' in the frame can vary and cause less or more pressure on the decoder. Sometimes this causes problems with the track contact end of things, but because of the wy the motor tabs get strapped down, the problem could be there as well. Common signs of the motor contacts being bad are that the lights work, but the loco won't move and you can't read CVs. Since other locos work, and can read CVs on the program track, there's nothing wrong witht he Zephyr or the wiring. It's almost certainly the motor contacts in this particular loco.

                --Randy


Modeling the Reading Railroad in the 1950's

 

Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.

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Posted by Stevert on Tuesday, October 21, 2014 8:21 PM

"d nr" means "decoder not responding". 

The decoder responds by pulsing the motor, so the places I'd check first would be the motor connections to the decoder, then the decoder to the frame halves.

In N-scale locos, those frame halves to decoder contact points are often an isssue.  A common fix is to blob a little more solder on the decoder tabs, but MR just had an article where the author used the alternative approach of wedging the contacts against the frame halves with a small piece of foam.

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Posted by richhotrain on Tuesday, October 21, 2014 8:27 PM

rrinker

 N scale immediately set off the warning bells - most likely the decoder is not making proper contact with the motor tabs.  

The TCS installation guide recommends soldering those motor tabs to the decoder square copper pads to ensure proper contact.

http://www.tcsdcc.com/Customer_Content/Installation_Pictures/N_Scale/Kato/EMD_F7A/EMD_F7A.html

Rich

Alton Junction

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Posted by RideOnRoad on Tuesday, October 21, 2014 10:51 PM

I was sure I had soldered the connection already so I didn't see any reason to take the shell off. I was right, I had soldered it; however, as it turns out, the joint had failed. I will redo the connection and all should be well. (I just don't get this whole soldering thing.)

Thanks for your patience with my ineptitude.

Richard

  • Member since
    September 2004
  • From: Dearborn Station
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Posted by richhotrain on Wednesday, October 22, 2014 4:47 AM

Thanks for pursuing it and reporting back to us.

Glad you got the problem resolved.

Rich

Alton Junction

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Posted by MisterBeasley on Wednesday, October 22, 2014 12:57 PM

RideOnRoad responded:

Thanks for your patience with my ineptitude.

You think you're special?  Most of us were inept clods at one point.  Asking questions and trying stuff is the only way out.

This was the most likely solution.  Given that you could turn the lights on and off, we should have known that the decoder was connected to the track and responding to commands.  It also had the address correct, because you could turn the lights on and off. If a motor wire is disconnected, the engine won't move, but it also will not respond to programming commands.  This is part of the "safety" aspect of DCC.  When you install a decoder, you should always try it on the programming track first, because this is one of those "wiring faults" that can be detected without damaging the decoder.

It takes an iron man to play with a toy iron horse. 

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