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Decoder is Fine But Loco Does not Respond in DCC Mode - Loco Does Run in DC Mode

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Decoder is Fine But Loco Does not Respond in DCC Mode - Loco Does Run in DC Mode
Posted by richhotrain on Wednesday, October 25, 2017 7:22 AM

I have an NCE PH-Pro 5 amp system.

Yesterday, I was running an HO scale steam locomotive (a Proto 2-8-4). It has a Digitrax DH163LO decoder.

It was coming out of a yard and crossed a turnout on the yard ladder. The locomotive stopped as one of the tender's wheelsets derailed. Nothing catastrophic. The locomotive and tender remained upright on the tracks.

I set the locomotive and tender on the mainline, but I could not get it to respond to commands. So, I moved it to the Programming Track, but without success. Cannot read CV.

I finally removed the decoder and tested it with my decoder tester (NCE DTK). It is fine and the long address was still stored in the decoder.

So, then I re-installed the original DC board in the locomotive and tested it on a section of DC powered track. It ran fine.

I have not yet re-installed the decoder, but I am wondering what could be wrong if the decoder tests OK, and if the locomotive runs fine, with its DC board installed, on a DC powered test track. All of the wires on the wiring harness look fine, no fraying, no melted insulation.  The plug into the tender is firmly in place.

Any ideas what is wrong here?

Rich

 

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Posted by SouthPenn on Wednesday, October 25, 2017 8:55 AM

Do other DCC locomotives run on your layout?

 

 

South Penn
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Posted by richhotrain on Wednesday, October 25, 2017 9:00 AM

Yep, everything else is running just fine.

Rich

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Posted by 7j43k on Wednesday, October 25, 2017 9:42 AM

richhotrain

 

Any ideas what is wrong here?

  

 

A loose connection that got "joggled" in the derailment.  And "joggled" at various times thereafter.

Or.

Some kind of "reset" caused by the derailment.  In my DCC life, I keep seeing and experiencing reports of things like sound-but-it-doesn't-go.  Which, if you don't have sound, could be doesn't-go.  I'd love an extensive article about this particular problem.

 

 

Speaking of the sound-but-doesn't-go problem, I finally (I hope) fixed my first engine ever that had the problem:  a Sunset "SP&S" 4-8-4.  Sound, but no-go.  Turns out I didn't have the plug fully seated in the engine-tender connection.  And by great good luck, it only failed at one of the motor connections.  Or so it appears.

 

Ed

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Posted by Stevert on Wednesday, October 25, 2017 9:57 AM

7j43k

Some kind of "reset" caused by the derailment.  In my DCC life, I keep seeing and experiencing reports of things like sound-but-it-doesn't-go.  Which, if you don't have sound, could be doesn't-go.  I'd love an extensive article about this particular problem.

Ed

 

 
This is (somewhat) common knowledge.  DCC works on the principle of square-wave AC with rather tight timing.  A short has the potential to distort that waveform into something that either scrambles the decoder, or gets interpreted as something other than a waveform that should be ignored.
 
That's why it's recommended to turn off analog conversion (DC) to avoid runaways - When there's a short, the decoder sees voltage but not a valid DCC waveform, so it thinks it's on a DC layout and just sends the track voltage to the motor.
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Posted by richhotrain on Wednesday, October 25, 2017 10:15 AM

By the way, the value of CV29 was set to 34 when this all happened.

Rich

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Posted by wjstix on Wednesday, October 25, 2017 11:18 AM

I'd agree, sounds like the short caused a change in a CV. I'd reinstall the decoder and reprogram it to the correct ID no. (engine no. or whatever you used) and see if that works. If not, do a factory re-set of the decoder and see if it works on ID 03.

(It could be that the long address is still in the decoder as you say, but a CV may have changed that allows the decoder to use the long address.)

Stix
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Posted by tstage on Wednesday, October 25, 2017 11:23 AM

I would just do a factory reset and readdress it.  If the decoder still doesn't work then you know the decoder was somehow damaged.  Then you purchase a TCS decoder and all your problems are solved, Rich. Smile, Wink & Grin

Tom

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Posted by richhotrain on Wednesday, October 25, 2017 3:00 PM

Thanks, everyone.

I followed your advice and reset the decoder to factory defaults. Then, I reprogrammed it on the Programming Track.

Everything works fine once again.

But, I still wonder why the decoder played dead and did not respond to any commands on the mainline and why the Programming Track could not even recognize the Manufacturer ID or Version Number of the decoder.

Rich

Alton Junction

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Posted by tstage on Wednesday, October 25, 2017 4:16 PM

Like Steve said earlier, sometimes a short just scrambles a decoder's brains and resetting it cures the issue(s).  Liken it to needing to restart a computer.  A least it's easier to reprogram a decoder than it is a computer.

It everything is running well again, Rich.

Tom

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Posted by zstripe on Wednesday, October 25, 2017 5:00 PM

It was tired with all the confusion and took a nap!..............

Take Care! Big Smile

Frank

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Posted by Midwest Northern R.R on Sunday, May 19, 2019 2:47 PM

On my DCC commander, after a derailment you have to give it about 5 mins to reset. 

Or,

Try allowing the decoder to rest overnight.

Here's to Advice!

"Your Never Too Old To Play With Trains"

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Posted by mbinsewi on Sunday, May 19, 2019 3:02 PM

It's been a year and 7 months, Rich is still active in here, but I think he fixed it. Whistling

Mike.

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Posted by richhotrain on Monday, May 20, 2019 7:42 AM

mbinsewi

It's been a year and 7 months, Rich is still active in here, but I think he fixed it. Whistling

Mike.

 

Yep, still here and, yep, solved that problem a year and a half ago. Never did get a definitive answer as to why the decoder played dead and needed a reset to factory default.

Meanwhile, the offending turnout is gone and the layout demolished in favor of a whole new layout. Almost forgot about this thread. Still have that locomotive and that decoder.

Rich

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Posted by wjstix on Monday, May 20, 2019 11:15 AM

Have you tried contacting Digitrax? Since they built it, they should know how it would respond in a situation like that.

My guess would be that the decoder is designed/programmed so that when it detects a short circuit, it shuts down everything so that the short doesn't destroy it, and that it is designed to remain in total shut-down mode and ignore all commands and attempts to read anything until it receives a signal that a factory-reset is being done.

Stix
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Posted by richhotrain on Monday, May 20, 2019 1:37 PM

Stix, if your reply is addressed to me, No, I never contacted DIgitrax. The reset got the decoder working again, so I just moved on. I nearly forgot about the issue or even starting this thread till a belated reply appeared some 19 months later.

Rich

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Posted by Midwest Northern R.R on Thursday, June 13, 2019 7:21 AM

Oops,

I guess I didn't read the dates on the replys.

Whistling

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Posted by richhotrain on Thursday, June 13, 2019 7:39 AM

Midwest Northern R.R

Oops,

I guess I didn't read the dates on the replys.

Whistling 

LOL

No harm, no foul.

Rich

Alton Junction

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