Startup Speed Bursts

[potlatcher]

I have two or three decoder-equipped locomotives that sometimes take off running, just for an instant, when I power up the layout.  I would like them to not do this.  I am using an NCE Powerhouse Pro DCC system, and the engines in question all (I think) contain some older NCE decoders.  Is this a typical problem, and is there a way to keep it from happening without replacing decoders?

If this has been copied on earlier discussions, please point the way to the earlier threads.

Thanks,

Tom

[jalajoie]

If analog operation is enable, turn it off.

[Hamltnblue]

You'll find your answer in CV 29.  Turn off the DC operation option on each loco.  Here's a CV29 calculator to make it easier. http://www.2mm.org.uk/articles/cv29%20calculator.htm

[cacole]

Reprogram CV 29 to turn off DC operation in the decoders.  I always give CV 29 a value of 34 for a long address to start, which tells the decoder to run normal direction, 28/128 speed steps, and no DC operation.

 

[tricky_trev]

yep. you're seeing the zero-stretching signal being read by the decoders. zero stretching is used for DC mode (loco address 00).

[rrinker]

 Well technically not since NCE doesn't do zero stretching to run a DC loco, it's just the waveform being unstable for a second while the processor initializes at power up. The result is the same, since the decoder doesn't see a valid DCC signal it assumes it must be on DC track and acts accordingly. Turning off the analog operation with CV29 is the solution. Just remember you did it in case you later take the loco to a DC layout and wonder why it suddenly doesn't run. If you only run your equipment on DCC layouts there absolutely no reason to leave the analog conversion turned on, even on locos that don't seem to have a runaway problem.

                                                  --Randy

[potlatcher]

Thanks for the several replied to my question.  I took your advice and turned off the DC setting on my problem engines.  So far, so good.

Tom