Front/rear lighting issue

[Kev48]

I have 2 n gauge diesels on which the front rear lights only work intermittently. I'm using a dynamis controller which has 28 power steps and the lights only work on the even numbered power steps and go off on the odd numbered steps and when stationary. One is a Farish loco and one Dapol, both with 6 pin decoders installed, one Bachmann chip and one Digitrax.

 

Would be grateful for any help please

[RFS]

This can happen if there's a mismatch between the speed steps set for the locos in the DCC command station, and in the decoder. For example, the decoder is set to 28/128 steps (usually the default) and the command station is set to 14/27.

 

If you're using 28 speed steps then both controller and decoder need to be set to the same value.

[Kev48]

I suspect it's the decoders as I have many other locos which have no problems. How do I reprogram the decoder?

[AMJ]

It might be something I have experienced where the decoder very briefly loses the signal from the track and lights then go off.  If non sound I press the F2 and lights come back on.  Probably dirty track or not enough wheels on the track at any moment in time.

[Adrian Wintle]

The issue, as mentioned above, is a mismatch of the speed steps. Ensure that the value in CV29 is correct for the settings that you are using. Try CV29 = 6 if you are using 2-digit addressing or CV29 = 38 if you are using 4-digit addressing.

 

Technical note - in 14/27 mode, the decoder uses 4 bits for the speed command and a 5th bit for the lights, while in 28/128 step mode, the decoder uses that 5th bit as the low bit of the (5-bit) speed command and the lights are controlled by a completely different bit in the message.

[Kev48]

Problem solved by altering CV29 value as above and all fine on both locos. Thanks for your help