DCC Chipped Loco & NCE system being tripped

[Damo666]

I'm in the process of wiring up my layout to DCC, taking the process methodically.

 

I've a Power Bus and a separate Accessory Bus, off which are the DCC Concepts Cobalt IP Digital Point Motors. Before I moved on to installing the point motors I simply wired all the track and tested each section on the board before moving onto the other tracks on the same board. All OK.

Then when I fitting the point motors, I tested their operation at each stage, giving them accessory numbers.

All seemed to be OK.

 

I then took a Class 08 shunter which is DCC chipped and started to run it over the points. My wiring seemed to be OK apart from two turnouts where my NCE PowerCab tripped. I cannot remember my exact next steps, but I continued to run the shunter over points to see where that trip was happening and at some stage the shunter just kept moving even though the throttle was at zero. I recall reading that this might be because the chip had reset and the loco is thinking it's running on plain DC. But before I could investigate this the loco ran over a point and the NCE again tripped.

 

Now the loco just trips every time it's on the track. I've a short test track for running-in locos or if I need to do any CV changes, and when I place the loco on this test track the NCE just trips, resets and trips again.

 

I'm guessing that something has blown. The DCC chip has a separate Stay-Alive. I'm not sure if a slight discolouration on the outside of the Stay-Alive is indicating that this has blown or not. (I cannot recall if I glued the Stay-Alive in the cab, if I did, this might be the stuff you can see on the door).

 

Anyone have any suggestions as to where I should start my investigations?

 

 

 

[Nigelcliffe]

A few observations. 

 

a)  a track short circuit should not damage a decoder, or a stay-alive unit.     Some (low quality) decoders can reset themselves from the spikes from short-circuits, but the decoder should withstand those.   

That you appear to have a faulty decoder suggests something else went wrong, possibly a fault present from when the decoder was installed.  

 

b)  You talk of "separate track and accessory bus" and then "cobalt IP digital".    If you are using the "frog" output wire on the IP Digital, then you've cross-connected your track and accessory buses at the frog, so defeated the point of your wiring to separate the two.     Instead should use the other change-over contacts on the cobalt to switch the frog.  

 

c) shorts running through a turnout suggests a wiring fault at/near those turnouts.   Or turnouts set incorrectly by operator. 

 

 

I couldn't diagnose anything from your photos.  

 

 

 

- Nigel

 

[Damo666]

Thanks Nigel.

 

6 hours ago, Nigelcliffe said:

a)  a track short circuit should not damage a decoder, or a stay-alive unit.     Some (low quality) decoders can reset themselves from the spikes from short-circuits, but the decoder should withstand those.

 

The Decoder is an 8pin DiGiTrains decoder which I got from DCCTrain Automation.

 

6 hours ago, Nigelcliffe said:

That you appear to have a faulty decoder suggests something else went wrong, possibly a fault present from when the decoder was installed. 

 

Loco ran OK on my rolling-road after I installed the decoder, and also OK on the layout for a while until 'something' happened.

 

6 hours ago, Nigelcliffe said:

b)  You talk of "separate track and accessory bus" and then "cobalt IP digital".    If you are using the "frog" output wire on the IP Digital, then you've cross-connected your track and accessory buses at the frog, so defeated the point of your wiring to separate the two.     Instead should use the other change-over contacts on the cobalt to switch the frog. 

 

A good point, and something that I hadn't picked up until earlier this week (and after the Loco problem appeared).  I had Cobalt DCC IN x2 wired to the Accessory Bus and the S1-Frog to the point frog.

 

I'm now amending the wiring so that the DCC In x2 takes the power for the motor off the Accessory Bus as before, but S2-L, S2-R takes the frog power of the track bus, with S2-C wired to the frog.

 

6 hours ago, Nigelcliffe said:

c) shorts running through a turnout suggests a wiring fault at/near those turnouts.   Or turnouts set incorrectly by operator.

 

Hopefully my re-wiring will find the problem, if that is where it lies.

 

Thanks

D

 

Edited April 10, 2021 by Damo666
Corrected Decoder manufacturer

[Damo666]

1.

I removed the DCC Decoder and reinstalled the blanking plate. Put the loco on the test track with a DC power supply and it runs sweetly.

 

2.

Put the DCC Decoder back in the loco and it still trips the NCE system.

 

3.

Removed the Stay-Alive capacitor and it still trips.

 

4.

Next step was to put the chip into another loco, this time a Bachmann Class 08. Bachmann runs perfectly on DC, but trips when I put the the decoder in and run on DCC.

 

So I guess that something happened which damaged the Decoder.

(And having taken the decoder out of the Hornby, I see that it's not DCC Concepts but a blue wrapped decoder which my record show is an 8pin DigiTrains).