Help me troubleshoot my TCS CN decoder install

[Bart1701]

I had an OLD Atlas N-Gauge GP-35 and purchased a TCS CN decoder. I need some help on troubleshooting my install.

I cut the motor tabs and soldered the wires to it. I wrapped the areas by the tabs/wires with Kapton tape so the tabs/wires would not touch the frame..

Cut a notch in the plastic motor bracket to run the wires up through.

Soldered the 3 wires to the rear board.

Put the locomotive on my programming track (I use a Digitrax Zephyr on my layout). The Address read back as 03.

Put the locomotive on the main line, selected 03, and was able to turn on the headlight and get the locomotive to run around the layout. Although, the headlight that was on was the wrong one for the direction it was traveling.

The locomotive was a bit noisy (due to its age), so I took it apart and lubricated it.

Put it all back together, and tried to change the CVs for the lights on my programming track. Not sure if I did that correctly, but put the locomotive back on the main and tried to get it to run. Nothing happened!

Now unable to read anything from the decoder on the programming track. All I get is a "d nr" (did not read) message.

I also discovered that when I put the locomotive on the main, turn the power to the layout off, and then on...that the locomotive starts running for about 2-3 seconds in the forward direction and then stops. Turn the power off and on again, and it runs on its own for a few seconds and stops. The locomotive is not selected on my controller when this happens. Neither headlight is lit, either.

I tried to do some amateur troubleshooting by using my track tester ( 2 wires and a lamp ). Touching the wires to the frame sides lights the lamp. Very carefully touching one of the decoder contact strips and the opposite side of the frame causes the lamp to light. Did this with all 4 decoder contact strips and the lamp lights. Also did this just by carefully touching two decoder contact strips (being careful not to touch any part of the frame) and the lamp lights.

All of this suggests to me that the decoder is making contact with the frame and is receiving power, especially since the motor runs when the layout is powered up.

What might cause this behavior? And what do I do to fix it? Maybe the decoder is bad and I need to send it back; but first wanted to make sure it wasn't something that could be fixed somehow by me.

Thanks much!
Bart

[mmyers]

Bart,
 Unfortunately it sounds like one of the motor wires may be making contact with the frame. Could have happened on the second reassemble. I would tear it down again and check the motor contacts to be sure they are isolated. You could test the decoder while the engine is apart to see if the decoder is fried. Jumper track power to the decoder track pick ups and try controlling the lights. If the decoder checks out OK, reassemble carefully and test again on the programming track.
BTW, you may want to do the Ron Beardon bearing block removal procedure to improve how the engine runs.

Martin Myers

[tehachapifan]

Having done an install of one of these fairly recently, I recall that it is necessary for all 4 frame contacts to be making very solid and tight contact with the frame (but be careful, too tight and the board(s) can crack if you try to force them in) . Also, I seem to recall that at least some CV changes required you to remove power from the loco for x amount of seconds before it would register correctly. Can't recall the specifics on that right now but will post if I do or I run across more info.

...also, what CV(s) did you attempt to change before it stopped working correctly except for light direction?

[Bart1701]

I tried to program the 4 digit address for the decoder following the Digitrax instructions for doing so. Whether or not it was successful, I don't know since I can't read the decoder at this time (the "d nr" response that I get).

The CVs that I changed were CV49 and CV50. I entered 16 and 0 respectively (and literally), as the TCS Install Guide suggested. Now, the dumb question - does TCS provide their CV values as Hexadecimal or Decimal values? The Digitrax Zephyr uses Decimal values for entering CVs, doesn't it?

I also tried later on entering a value of 2 into CV8 to attempt a Factory reset.

Thanks,
Bart

[Bart1701]

One more response...

I think the 4 decoder tabs are making contact with my frame. Since I used my tester to touch a wire to one side of the frame and the other wire just to the decoder pads on the opposite side. Every pad test showed that current was passing through each pad.

I plan on taking it apart and doing the tests that Martin suggested.

Bart

[tehachapifan]

Do you have or have you referenced these documents?

The first shows an installation with pics in an older Atlas GP35 starting on page 14 that you can compare your installation to. I noticed there's a section about having to modify the frame below one of the boards...

https://www.tcsdcc.com/Customer_Content/Technical_Info/Tech_Manuals/TCS_Book_of_Classic_N_Installations.pdf

The second is the basic CN-GP manual...

https://www.tcsdcc.com/Customer_Content/Literature/Decoders/N_Scale/Classic_N/CNGPBEMFWEB.pdf

Is yours the CN or the CN-GP? I think the only difference is the board shapes, but I'm not positive. Here's the CN manual...

https://www.tcsdcc.com/Customer_Content/Literature/Decoders/N_Scale/Classic_N/CNBEMFWEB.pdf

[Bart1701]

Thanks for the links, Russ. These were the instructions I had used while installing the decoder.

I took the decoder and motor out of the frame, used jumpers to connect the rails on my programming track to all 4 pads of the decoder. That should eliminate any issue with the motor wires making contact with the frame.

In Digitrax Page mode of programming, I tried to read back Address2 ( and also Address4 ) to see if would read the decoder's current address. All I get back is the "d nr" (did not read ) message.

If I connect the jumpers to the main line and turn the power on to the layout, the motor still starts running at a moderate speed for about 2 seconds and then stops. Turn the power off and on again, and the same thing continues to occur.

Thanks,
Bart

[peteski]

That unfortunately seems to indicate that you somehow bricked/fried/killed the decoder.  The way it behaves seems to indicate that it is just the microcontroller's programming that got scrambled.  But there is nothing you can do to fix that.  Good thing TCS has a good warranty.

[Bart1701]

I have sent TCS an email documenting my issues. We'll see what they say!

I have installed many decoders and I think I only managed to fry one so far. It looks like I may be up to two now!

I'm glad that the decoder companies have their "goof-proof" warranties to protect us from ourselves.

Bart

[peteski]

Is it possible that you zapped the decoder with static electricity (from your body)?  That can sometimes kill the decoder's internal programming. Where I live (Northeast USA) static electricity is really potent during the cold season (the air is very dry, not dissipating static, so I get shocked almost everywhere I touch a metal object).

[tehachapifan]

Looking forward to hearing what TCS has to say. Hopefully there's still something you can try before having to send it back, like maybe another reset attempt. I found some info online that says factory resets should only be done on the program track and must be followed by a power down and power up. One source says the power-down thing is for "older" TCS decoders only....whatever that means.

[peteski]

I found some info online that says factory resets should only be done on the program track and must be followed by a power down and power up. One source says the power-down thing is for "older" TCS decoders only....whatever that means.

That can mean the older-design decoders (hardware-wise) or ones running older version of firmware (or both). But unlike Digitrax, the decoder model numbers TCS uses do not include the version/generation ID.

So unless you know more details and can read out the CV register in the decoder which stores version number (assuming TCS does update that CV), then you really don't know what version (or age) the decoder is.

Digitrax numbering system makes identifying the decoder versions (and their features) much easier.

For example, take the DZ12X decoder:  Even though the decoder is the same (in amperage and in number of function outputs), DZ121 (or was there even a DZ120?) is the earliest version and DZ126 is the latest.  There was also a DZ123 and DZ125 (intermediate versions). The decoder also got physically smaller but has the same number of functions.  With TCS there is no easy way to tell whether the CN decoder you bought now is the latest or the original release (or if there even were any changes to its firmware).