# DCC loco stall/stops



## Gwpapa

I have one DCC loco that sometimes stops on top of one of my turnouts. My other locos manuver through the turnout fine. All my other locos have the decoder and keeps lives mounted in them and no track pickups in the tenders. This one loco has power pickups in the loco on its right side and in the tender on its left side. It has a keep alive installed but still stops with the loco on one side of the frog and the tender in the other. 
The loco just appears to freeze in place. Not all the time but once every 5-6 trips around. The sound is still working also the light but no movement. None of the power cab functions work as if the loco is not responding to the commands. If I unplug my power cab then re plug it the loco will start up again. If I tilt the loco and tender over slightly then back on track it will take off at the preset speed. If I just move the loco farther down the track it still will not go until I pick it up and place it back on track. I have checked voltage on every piece of track and found nothing wrong. What would cause a loco with a keep live to stop dead still?


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## DonR

Does this event have any effect on any other loco running
at the same time?

I'm thinking that there is the possibility that this loco and/or tender has wide
treads on it's wheels that momentarily short across the insulator
in the frog, thus tripping out the decoder. That could be why
it runs through the turnout most passes, but on some the wide
tread makes contact. Is there lateral movement of
the loco axles that could cause this also.

When you removed power any of the ways you describe you
are in effect resetting the decoder. (Or the Controller itself, which
is why I asked if other running locos were affected)

My Bachmann EZ main controller will default to loco # 1 anytime
it gets a momentary short of this nature. 

I use a tiny dab of clear fingernail polish at the
frog where the rails have a slim insulator 
separating them. 

You might try that and see if it helps.

Don


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## Gwpapa

No other locos are effected when this happens. I don't think the decoder is completely shutting down just the motor function is effected. The sound and lights continue to operate. If I tilt the loco to its side slightly or just enough to break the contact with the track the loco takes off at the speed it was running. The headlight does blink for an instant when this happens. When it stops it is not effected by any commands from the power cab.


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## Gwpapa

I should have said that the headlight blinks at the same time the loco freezes. If I pickup the loco and set it back down it continues at the preset speed. It does not restart like when I powed down and then up the power cab.


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## DonR

That is a quite different malady than we've heard of before.

What brand decoder and DCC system? Some who use that may know a setting that could be wrong.

From what you say, any kind of break from the power will
cause the loco decoder to 'reset' when it has stopped on it's own.

I have not experienced that. If you have checked the
loco with the shell off and found that all wiring is solid
and there are no loose parts, my guess is that you
have a decoder that reacts to either/or both a momentary
short circuit and a momentary loss of power.

I wonder if we can test for that.

If you could connect a separate test track to the DCC 
controller and put only this loco on it. Have it run
at your usual speed. Then take screwdriver of other
metal object and make a momentary short across the
rails close to the loco and note it's reaction. A momentary
short would be a quick touch and go. The light should
blink once.

Then the same as above but have one wire of the
DCC line loose so you can press it against the track
to run the loco then momentarily remove it then
quickly restore power and note the reaction.

If either of these cause the loco to stop then use the
'loose' wire to interrupt the power again and see if
that 'resets' the decoder so the loco will run.

Don


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## Gwpapa

Don, thanks the decoder is the Digitrax SDXH166D and a Power Cab controller. I will try the test you mentioned later today.


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## Gwpapa

I tried the short across the track and if it is only for a fraction of a second nothing happens. If I short across the track for a second or so the loco stops dead and the NCE reboots. Once It reboots the loco will respond to whatever command it get. 
When removing one of the tracks power leads the loco will run about one foot further until the keep alive dies. The sound will last 3-4 seconds longer. Reconnecting the track power lead causes the loco to resume it normal speed setting whatever that was before the interruption. Just briefly removing the track lead then reconnecting it doesn't effect the loco. 

FYI when the loco stops on or near the turnout the sound continues the light stays no but the loco stops and it want respond to any command. Only removing it from the track or rebooting the controller will allow the controller to resume contact with the loco.


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## DonR

So neither the short or 'power off' test caused the
loco to 'shut down' and need the reset, yet, something happens on
that turnout that does cause the decoder to 'shut down'
until you interrupt power by lifting the loco or
rebooting the controller.

Also, you say the 'stay alive' kept it going when you pulled
the power in the test, yet it does not when the loco stops on the turnout.

Another result of the test, the loco ignores a momentary short and
continues on, but when you do a 'solid' short the loco stops, I assume
because, the NCE reboots. 

This is real Alice in Wonderland stuff, nothing seems to cause
the shut down, yet something does on the turnout.

There's one more thought that comes to mind. Where exactly
in relation to the frog and the points are all wheels of the loco
when it stops. I think you said it suddenly stops, it doesn't
continue with the 'stay alive'.

Let's hope one of the Digitrax or NCE guys will recognize something
in these symptoms.

Don


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## Gwpapa

I also tried a few things that may help. The loco doesn't always stop in the same spot but does within about two inches each time. The frog appears to be the issue because the loco normally gets past it but the tender stops right before,on top or just past it. I also found the slower it goes the better it passes over where the faster it goes it almost always stops. I am thinking now that the loco is shorting its self someway on. The spot right before the frog where the two rails almost meet. I think that is the spot you were talking about earlier. I have a photo and short video I will try to post in a few. Thanks!


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## Gwpapa

i have attached a photo of turnout. The spot i have circled in red looks to be the place most likely to cause the short. if it isn't that i don't know what is going on. i have a video of it stoping and then me restarting it if i can get it on here.
Hope this helps.


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## Gwpapa

i forgot to add that the train runs from right to left now


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## DonR

You mention that the train direction is different. Did that
eliminate the problem on the turnout?

You could try putting a small dab of clear finger nail
polish right at the point when those two frog rails
are so close. That would prevent the wheels shorting
across them. It makes sense that some electrical event
occurs on this turnout so this short prevention could
do the job.

If that doesn't help
there's one thing I should have thought of before all
the testing. Do a reset to factory default of the decoder.
You'll have to read your manual for the 'how to', my
Bachmann controller would do it differently than your
NCE. This has resolved odd problems on some decoders
in the past.

The default settings will change the locos address to #3
again and any special CV settings you had would be
changed to factory setting.

Don


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## Gwpapa

I started with it left to right when it was a DC track. When I changed over to DCC and found I could run two trains in different directions I changed it to right to left. I am going to try the polish first. I really think now that that is the problem. We will see!


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## Gwpapa

Here is a short video of the loco stopping in the turnout. i started out slowly and increased the speed untill it stopped. if you have sound you can hear the horn and bell. The throttle is still set about 70 on the speed scale. if you can see it the loco starts back up as soon as i drop it back on the track at the speed it was running.

https://www.youtube.com/watch?v=a2QxSQdqiTU


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## JerryH

My first suspect is the decoder itself. The problem is triggered by a minor electrical with the track problem though. I think the reboot of the decoder by the removal of power long enough to cause the reboot gets around what ever issue the decoder has.


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## Gwpapa

Well at least I have eliminated a few things. The fingernail polish didn't work. I even used masking tape to be sure nothing could touch the opposing track causing a short. I reset the decoder and that didn't help. It doesn't matter which direction the loco is going it still stops there. I can't find a flaw in the turnout anywhere and my other locos still manuver through there just fine.


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## DonR

Yes, Jerry, as you can see we've tried all sorts of tests and
suggestions.

There's no doubt something is triggering the decoder to shut
down the motor, leaving the lights and other functions available
to the controller.

We tried shorting the track near the loco and interrupting the
power neither seemed to trigger the shut down.

I notice from the pic of that turnout it has a long insulated frog.
The power pickup is from loco wheels on one rail, tender wheels
for the other rail. It may be that the long frog causes a very
short power break and that somehow trips the decoder. A second
power break (tipping the loco) resets it and the loco continues to
run. That seems to indicate some sort of defect in the decoder
unless you know of some CV setting that could overide the shutdown.
It's a Digitrax Sound decoder.

Don


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## Gwpapa

I am not sure if it means anything but, my other locos have KeepAlive2 with them. They seam to travel 2-3 feet after removing the power from them. This loco has the Power Xtender from Digitrax with it. This loco only moves about 2 inches when the power is removed from it. The sound continues a few seconds longer. It looks to me like the power Xtender is not doing much. I wonder if that adds to the problem?


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## DonR

It appears that the time has come to get in touch
with Digitrax and tell them everything we have
done. After giving them their model number and describing
how the loco comes to a stop, ask
them if they have had decoders shut down the motor
after a momentary power cut as the loco goes over
an insulated frog and leaving the lights and sound
operating. 

Is this decoder new enough to be covered by warranty?

Don


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## Gwpapa

Thanks it is only about two months old and I actually sent them up an email earlier today. I didn't know anything else to try. We will see what they say.


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## CTValleyRR

Defective merchandise happens (maybe a little more often with stuff made abroad). Getting a defective product isn't an issue as long as you have a strong company willing to stand behind what they sell.

You're in good hands with... Digitrax.


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## Gwpapa

Wow Digitrax replaced my decoder today. Sent it in last Friday and they tested it and said it was defective. They sent a new one I can't wait to see how it works. It took them only one week to get it back! Hope it goes over my turnouts and frogs. I will know tonight!


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## Gwpapa

Well I still have problems. I am beginning to think the Digitrax decoder and the NCE Power Cab don't work well together. Anyone else having issues with those two? It still starts, stops, stalls and just doesn't work well. They said the first decoder was defective but this one does worse than it did. My other decodes and locos run fine.


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## JerryH

How dirty are the wheels and or pickups on this particular loco as compared to the other locos? I had a Proto 2k that had bad axel/bearing electrical flow through them that caused very similar problems. After all the axel/bearing assemblies were replaced, no more problems.


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## Gwpapa

I have cleaned the loco and all the wheels, axels and checked the pickups etc several times. I can't find anything there to fix.


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## DonR

You got any hair left on your head?

This is a real poser.

Going back to the power pickup. Can you tell if the wipers are
making good contact with either the back of the wheels or
the axle whichever method is used? It's possible for the
wheels to move laterally and lose contact with the wiper.

I think you said that the loco wheels pickup one rail current
and the tender picks up the other rail.

I just added wipers to the other side of a truck to improve
power pickup. If the tender uses a wiper against the back
of the wheels it would be easy to add a wiper to the
side with none. Even if it has the wiper on the axles you could
still add a wiper to the rail side not being picked up if those
wheels are metal with smooth back. Most
hobby stores have thin brass sheets. You can cut it with
a scissors to make the wipers.

Don


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## Gwpapa

I "may" have solved my stall issue. Not positive but hopeful. I found that the frog on the offending turnout is very slightly higher than the track on either side. When I found this I started filing it down and the loco seamed to run over it much better. I didn't finish the filing but the loco ran about 30 mins without a freeze or stopping. I still don't understand how or why that would cause only that one loco to have problems and it has a keep alive installed. Anyway I will get back on it tomorrow and keep my fingers crossed.


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## JerryH

I suspect that the unpowered frog and the short wheel base without all wheel pick up is the issue. Maybe the different keep alive types are why the other loco doesn't have an issue.


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## Gwpapa

I think you may be right. This loco has the tender/loco pickups with the digitrax PX or their power extender. They tested it and the old decoder and said the old decoder was bad but the PX was fine. The other locos are all loco only pickups with other brand decoders and their KA Keepalives installed. Who knows?


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## DonR

If it's running maybe best to leave it alone, but if
you start having more of those 'stalls' I'd sure 
add to the power pickups. The tender would
be fairly easy and would be a good place to start.

Don


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## Cycleops

Gwpapa said:


> Well I still have problems. I am beginning to think the Digitrax decoder and the NCE Power Cab don't work well together. Anyone else having issues with those two? It still starts, stops, stalls and just doesn't work well. They said the first decoder was defective but this one does worse than it did. My other decodes and locos run fine.


Just to let you know I have the Powercab and all my decoders are Digitrax bar one and have had no issues.


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## Gwpapa

I ran it for about an hour with no problems today! Never stopped once. Thanks guys for the help.


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