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Troubleshooting a Dead DCC Loco

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  • Member since
    February 2002
  • From: Reading, PA
  • 30,002 posts
Posted by rrinker on Friday, November 27, 2015 11:27 PM

 Unless it was a very low current power supply, applying DC to the motor outputs of the decoder will almost CERTAINLY fry the motor driver. At best, the motor drive chip is designed to read the BEMF from the motor and that's it, not have a constant up to 12V DC applied across it. You might get away with a second or two of touching power there, but not running the motor for any significant amount of time. Once the motor drive is shot, the decoder will likely not read or acknowledge programming, since the most common way of doing this is pulsing the motor to generate the current spike. You may have lucked out, but odds are the motor drive is now dead.

                        --Randy


Modeling the Reading Railroad in the 1950's

 

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

  • Member since
    April 2004
  • From: Ontario Canada
  • 3,574 posts
Posted by Mark R. on Friday, November 27, 2015 7:38 PM

The motor output terminals of a decoder are connected to circuitry designed to output a pulse width modulated 12 volts DC .... it is not designed to accept the input of 12 volts DC.

Will it damage it ? .... maybe, but why take the chance ?

Mark. 

¡ uʍop ǝpısdn sı ǝɹnʇɐuƃıs ʎɯ 'dlǝɥ

  • Member since
    January 2010
  • 2,616 posts
Posted by peahrens on Friday, November 27, 2015 7:10 PM

Since the correct answer is likely yes, I'll take the 5th. 

But please do explain why DC voltage at the decoder output would hurt it when it's not powered from the front end (is that the implication?).

Paul

Modeling HO with a transition era UP bent

  • Member since
    April 2004
  • From: Ontario Canada
  • 3,574 posts
Posted by Mark R. on Friday, November 27, 2015 6:58 PM

You did disconnect the decoder from the motor before applying DC voltage to the motor to test it didn't you ?

Mark.

¡ uʍop ǝpısdn sı ǝɹnʇɐuƃıs ʎɯ 'dlǝɥ

  • Member since
    January 2010
  • 2,616 posts
Posted by peahrens on Friday, November 27, 2015 4:52 PM

I repeated steps from the other day and got similar results.  No program track read of CV8, no response on prior nor address 3 (in case a reset attempt had worked).  I did verify that a twin setup on a SD50 does read ok on my program track.  The faulty one still has a light blink very briefly when rocked on the track, and when sitting the decoder gets pretty warm. 

I discussed with Lou at Tonys Trains and he suggested jumpering from the program track to the decoder input wires, to bypass any potential pickup issues.  I did that and no results.  Tried to read CV8, reset it, etc, no dice.  I then applied DC to the motor leads and verified that the motor and mechanism is fine. 

So I'm guessing there's a decoder problem, unless the lights or speaker wires recently created a short that is making the decoder act this way.  Maybe before completely disconnecting it I'll disconnect the lights and speaker connections first, then verify that it (motor) still won't work with just the Ops/Program track input wires attached.  I think my wish list needs to add a decoder tester.

So next I'll call ESU to ask about sending in the decoder as it's less than a year old.  If I order any others near term I'll get one with SD50 sound, and if ESU sends a replacement I can use it in another loco later. 

Of course, I'm wondering what can cause whatever the problem is, but that's getting ahead of verifying a bad decoder.  

Paul

Modeling HO with a transition era UP bent

  • Member since
    December 2004
  • From: Bedford, MA, USA
  • 21,483 posts
Posted by MisterBeasley on Friday, November 27, 2015 10:19 AM

My Tsunami decoders run at a temperature that I would call "hot."  However, that's normal for them, apparently.

Do you have any control of lights?

Does this decoder have a "shutdown mode?"  I have a few like that, and when it's been shut down it's necessary to press F6 to bring it back to life.

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

  • Member since
    April 2004
  • From: Ontario Canada
  • 3,574 posts
Posted by Mark R. on Thursday, November 26, 2015 4:53 PM

To narrow the problem in half, you need to remove the decoder and temporarily wire the trucks straight to the motor and test it on straight DC. If the engine works fine on DC, then that eliminates the engine itself and points to the decoder.

A factory reset usually cures 99% of all programming glitches. The fact that it's "hot" is never a good sign. They will run warm, but not hot.

Mark. 

¡ uʍop ǝpısdn sı ǝɹnʇɐuƃıs ʎɯ 'dlǝɥ

  • Member since
    January 2010
  • 2,616 posts
Posted by peahrens on Thursday, November 26, 2015 4:04 PM

The LokProgrammer and a program track booster are on my wish list but may be months away from getting purchased and installed. So far it's a wiring diagram and a couple of DPDTs needed.

Paul

Modeling HO with a transition era UP bent

  • Member since
    January 2010
  • 2,616 posts
Troubleshooting a Dead DCC Loco
Posted by peahrens on Thursday, November 26, 2015 1:07 PM

I have a HO LifeLike P2K SD60 that I acquired and converted to LokSound Select (Aux6 hard wired in) with added speakers a number of months ago.  Not having run things much lately I decided to clean the track and move locos around and found this one not responding at all. 

It was assigned its 4-digit address, DC analog turned off, and was in consist with another so with my NCE PowerHouse Pro 5A I attempted several things.  I put it on the program track and tried to read CV8 for the manufacturer ID (that normally works with my setup).  Not read.  So I arbitrarily tried resetting with CV8 = 8 and power off / on.  Nothing.  Would not rsepond to address 3 nor its 4-digit address.  Of course now I don't know who it thinks it is.

Today I decided to begin an exam.  I put it on my DC test track.  With the DC cranked up most of the way it started making some engine sounds and a light came on.  After a bit it moved.  But with direction reversed it did nothing.  Could not get it to move again.  Cleaned the wheels, not the problem.

Then I removed the shell and put it back on the layout to try a CV8 read (no dice) and another reset.  No change in it responding to either address.  But then I noticed if I rocked it on the track a light came on very briefly, then went off, as the second set of wheels touched the 2nd rail.  So I'm pretty sure it's not a pickup problem.  And the decoder (not the motor) was very warm (maybe hot).

So I don't have a way to proceed and welcome advice.  It's neatly hard wired in so I'd love not to have to break connections but expect that might be needed.  For instance, to run the motor I'd have to expose some wire on the motor leads to connect some DC.  Do I need to remove the decoder and "test" it? I don't have a tester (is it inevitable that I'll need one?).  I see they are warranted for 2 years, so should I discuss with supplier, Tony's, and maybe disconnect and send it to them?  

Any help most appreciated.  And Happy Thanksgiving.  I'm thankful this is my biggest current problem.

   

Paul

Modeling HO with a transition era UP bent

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