Newly chipped loco not controllable on main layout

[Chappers]

I am having a baffling problem.

 

I have a Lilliput Cl62 (DB 4-6-4T) which I have decided to fit with a decoder (NEC DS15SRP) which I was given for Christmas. 

 

After I fitted the decoder I tested the loco on a DC section of track before placing it on a programming track and programming the number. The loco responded properly in both places. I move the loco to the main line of our club layout and loco will not respond. After a short time it may begin to move (not slowly) but not necessarily in the direction it was being commanded and would then not respond to any stop, change direction or any other commands. This is obviously very disturbing and unsatisfactory.

 

I have placed the loco back on the programming track and it will once again behave impeccably. I was also able to operate the loco normally for well over half an hour on a DC layout with the chip still installed. 

 

Back on the programming track with the help of another club member with Decoder Pro was able to read the decoder with no errors and program CVs. We switched back to the main-line and the erratic uncontrollable behaviour returned immediately. 

Finally we programmed the address to a completely different number, wondering if there was an address conflict. Once again it behaved fine on the programing track and DC but uncontrollable on the DCC mainline.

 

Have anyone encountered similar problems, especially with the same loco or decoder?

 

I am at a loss what next to do, especially as disassembling the loco to remove the chip is a very intricate and potentially damaging process.

 

Any advice gratefully received

[34theletterbetweenB&D]

Standard advice with any sort of decoder malfunction of this sort is a decoder reset. Once the decoder is back to factory default address 03, reprogramme and test on  DCC power.

 

Don't test it on the DC section. There may be signals present that your decoder cannot handle: hf track cleaners or lighting, pulse modulated controller outputs and the like. (Disabling DC running in CV29 might be a good plan while programming the decoder, unless you specifically want this facility.)

[Phil S]

After testing on the programming track...which often has a reduced current limit to protect new installations, use a simple 9V battery applied across an isolated piece of track to check DC performance on guaranteed smooth DC

 

Beware that many so called DC controllers such as the very common H And M series are totally unregulated and unsmoothed in their output voltages.... Which can also easily exceed 22V at their peak ... 100x a second !!! Quite often a decoder fitted loco will not work correctly under these conditions, or sometimes, never again !! HF track cleaners adding their signal can also be a problem. However you appear to have got away with it in this case... Perhaps the DC controller is a modern electronic one with regulated output or like (eg) a gauge master I have with HF pulse width output that is seen as smooth DC. (Many early 'electronic' Pwm/feedback controllers were 50/100Hz mains based ...not DCC compatible)

 

You don't mention what DCC controller is used for the club main layout. I have found that some NEC devices are only rated to 16V. Instead of the full 22V+. So it may be worth measuring accurately the DCC track voltages eg with a rampmeter or oscilloscope or. Via a bridge rectifier and adding in the bridge's voltage drop of about 1.4V

 

A final thought... Does the main layout have Railcom...the NEC decoder may not understand this????

[Chappers]

The layout is NCE throughout and control was tried with bot Powercab, Procab and CAB06 controllers. As I don not have a layout or test track at home I will not be able to try again until my next visit

[brossard]

Your home test track can be as simple as a yard of track.  I mounted a length on to a board using alligator clips to connect the controller, DCC or DC.

 

John