Analogue Coach Lighting Interfering with DCC ABC braking? 

It's not bridging the gap here -- because I switch the entire block into ABC when the first vehicle gets to a certain point. That's so I can cope with trains being propelled, with the loco at the back.

@@DongitsModelRailway so it the cap on the cheap lighting smoothing out the signal ? Never tested it but I guess that's what would happen

@@johnjmc As best I can tell the difference in voltage between the positive and negative phase of the DCC is causing a difference in power draw on both phases into the capacitor -- high on the higher side, low on the lower side. That's creating a different level of voltage drop, which was sufficiently reducing the difference in the ABC signal at the (larger, and modular) club layout. At my (smaller) home layout it was still working fine.

The cabling difference is why I think I found this at the club layout (with circa ten board jumpers on the main bus and a bit over double the wiring length end to end) and not at home. In both cases though, we solved the entry into the ABC section by switching the whole train over in one go (when the last block is occupied, all the blocks switch over at once) so there's no non-ABC signal to bridge in. In terms of the light conversion in the coach, that's exactly the kind of thing I was thinking of, but I still dislike the really minimal illumination provided by the fibre optic table lamps. When every other coach was unlit, it probably gave a suitably subtle effect to include one of these in a rake of unlit coaches. But put one of these next to a Bachmann Mk2F and it does not look at all like a lit coach. I'm not sure fitting an LED and ensuring the optical fibres line up will change that -- it'll still need something fitted overhead too.

@@DongitsModelRailway It's not just the cable length but the cable type - solid cable can have up to 12x the impedance on dcc frequencies than multistrand control wire (strand diameter / sqmm matters), it's a very different world to sinusoidal 50/60Hz operation. Yes, switching the whole section is one way to avoid the wheel/ bogie/coach circuit bridging issue and glad you could resolve. This was something I concluded has to be done with stop on dc - a short as the wheels bridge dc to dcc would be rather destructive and so I am leaving that on the back burner! When I took up with a major supplier of dcc chips they could not produce either an application note or say how they tested them when developing the product - not good for any users nor does it instil confidence in their product development and validation procedures! I have thought about the ABC (which is more attractive than stop on dc) problem and realise the other way is a solution using a short island of track isolating the ABC from the DCC sections length and using a resistor potential divider ABC to DCC supplying that island at the centre tap, figures work alright with up to 300mA of loco current and good for the bridge R-C to LEDs in the coaches I mentioned above - no need for anything else - it looks after itself. Nice to see you have the same scope as me - excellent value for money! Anyway, glad you are sorted out.

@@stephenpike3147 Yes, there are many factors about the cable that can make a difference. I'm sure Copper vs CCA will make a difference too. In my case, all the cable used is multi-strand with the exception of droppers that go from the rail to just below the baseboard, and I try to use only Copper, no CCA, although I think there's some CCA used in the club layout.

If I did that I'd need to add something to make them electrically live for train detection. I may as well improve their ability to take track power if I'm going that way - no sense in making them take track power, do nothing with it, and then power lighting with a separate circuit.