Minor train crash, major decoder problem

[Nomis]

My pendolino with two R8249 decoders has suddenly gone mad after a minor crash.

lights on dummy car no longer works. lights flash repeatdedly as the train jumps backwards.

 

Not impressed with the snowflake nature of these chips.  Have opened trains, no shorts, pink wire trimmed of exposed tinning etc.

 

Can anyone help?

[Chrissaf]

During the crash there may have been a transient short circuit that has corrupted the decoder configuration. Subject to your controllers capability you could try performing a factory reset on the decoders (write value 8 to CV8). Note that if successful, this will revert all the settings back to the factory default. So any changes you made, DCC Address for example' will need to be redone. The factory default DCC address being 003.

[jane1707819582]

have a quick check with your pick ups 

do the lights flash going forward ?

does the power car jump when travelling forward ?

[2e0dtoeric]

The first thing that comes to mind is a bad electrical connection. Check that the wires from your controller to the track are good, solid, and clean, the track power connector is a tight fit Then make sure the track and wheels are clean!

If you have used the very fine wires that are sometimes supplied, and you move the controller about a lot, you could have a break in the wire inside the plastic casing, which is causing very brief interrupts to the digital signal, and as a result, the decoder is thinking it is seeing an analogue voltage of 16 - just for an instant - and thus causing the loco to try to go at 600 mph until the decoder recognizes a DCC signal again.

Dirty wheels and/or track will have a similar effect.

[Nomis]

have a quick check with your pick ups 

do the lights flash going forward ?

does the power car jump when travelling forward ?

There is absolutely no control over the train or its functions.  I'm slightly annoyed that it's that easy to cause a problem with the decoders.

[Nomis]

During the crash there may have been a transient short circuit that has corrupted the decoder configuration. Subject to your controllers capability you could try performing a factory reset on the decoders (write value 8 to CV8). Note that if successful, this will revert all the settings back to the factory default. So any changes you made, DCC Address for example' will need to be redone. The factory default DCC address being 003.

I have tried to reset with this method several times, I have taken the train apart several times.  Nothing is helping.

[Traincliff]

Hi. Are you doing the reset on a programming track? I think that is quite important. 

My friend has the Olympic Javelin set and when we first chipped using same as you we had lots of problems with sudden runaways and reverting to code 03. We got over this totally by turning the ability to run on DC off on CV 29. What was happening was that the unit was seeing any breaks in supply to the decoder as a DC pulse and then running away or even reversing at high speed. The change to CV 29 resolved the issue totally. 

Try not to blame the Hornby chips they are ok within their price range. I have had same problem with B.........nn chips too until I learnt about cv29.

Hope you get it sorted.

Cliff

[Fishmanoz]

Cliff is talking about DC Runaway which is characterised by the loco taking off flat out forward or reverse and can only be stopped by removing track power. If your loco isn’t doing that, it’s not DC Runaway.  But to fix it in CV29, go to the 2mm.org site for their handy calculator.  It’s at http://www.2mm.org.uk/articles/cv29%20calculator.htm and you’ll see you need to subtract 4 from the current value of CV29.  The usual default for this is 6, in which case change it to 2.