A loco runs well on one DCC system but is unstable on another - why?

[selset bill]

I have recently obtained a DJ Models/Hattons 14XX loco.  I fitted it with a decoder and it ran very erratically on my home layout which has a Lenz DCC system.  However, on the local club's Digitrax powered layout it ran perfectly with the same CV settings. 

This loco has a coreless motor so I was expecting that there might be some CV changes needed to cater for the different feedback characteristics of coreless motors, but why should its stability depend on which DCC system is used?  I thought they all met the NMRA standards so ought to have identical outputs, but it seems not.  The differences must be subtle as the rest of my 50-plus loco stock works equally well on any system.

I should add that I don't believe it is a decoder problem as I tried decoders of different makes, with the same result.

 

Has anyone else had this problem?

[34theletterbetweenB&D]

You might want to eliminate the home layout from the potential contributors to this problem, by testing the loco with your Lenz system supplying only a wholly independent length of track.

 

If the problem is still present, then I suggest returning the unit for Lenz service to investigate, with the problem description.

[selset bill]

Thanks folks.  I've disabled railcom but it hasn't made any difference.  The decoders I used were up-to date ones anyway (from TCS and DCC Systems) so should be railcom compatible, but it was worth trying.

I will try hooking up my Lenz system to the club layout in place of the Digitrax one, then, as you say, if the problem is still there it's down to Lenz and not my layout.

[nick_bastable]

Thanks folks.  I've disabled railcom but it hasn't made any difference.  The decoders I used were up-to date ones anyway (from TCS and DCC Systems) so should be railcom compatible, but it was worth trying.

I will try hooking up my Lenz system to the club layout in place of the Digitrax one, then, as you say, if the problem is still there it's down to Lenz and not my layout.

voltage may be the issue ie the ref voltage of the decoder 

 

Nick

[RFS]

Have you removed the capacitor from the loco as this can sometimes interfere with the operation of the decoder.

[GoingUnderground]

Ah yes, the dreaded RailCom cutout effects. Your Lenz system has RailCom enabled by default, and older decoders (and those from across the big pond) cannot cope with the techniques used. Fetch your Lenz system's manual and shut down RailCom. Be aware that if you update the Lenz in the future, you need to repeat the performance.

 

Having said that, RailCom is specified in the NEM and NMRA standards, so recent US decoders should be able to cope.

If a different decoder that is fine in another loco produces the same problem, then the cause lies in the loco. I would try removing the TV/Radio interference supperssion components from the loco.

 

But first, do check that a decoder that has been in the loco still works correctly when reinstalled on a different loco in case the loco is causing damage to decoder.