Tempfix Rich Papper Posted June 22, 2017 Tempfix Share Posted June 22, 2017 Hello. I am hard wiring some DMU bits together and have got myself stuck. I'm afraid my level of knowledge with DCC is a bit pathetic. I am happy building things from scratch, adding pickups, lights, sound etc, but if after connecting all the same colour wires to each other it doesn't work, I don't really have a clue as to why. So I'm hoping someone out there can explain what on earth I've done wrong here. DMU. Power car is a Hornby (ex Lima) 101. I have added blue, yellow, white, green wires to the DCC socket and connected head and tail lights and internal lights. All work perfectly, run it all round the layout, both directions - no problems. It has a Hattons decoder. Trailer car is a conversion, but essentially a Lima chassis sitting on some spare Bachmann bogies I had so ready made good pickups. I have wired in the same head and tail lights and interior lights connected to a Hornby Sapphire chip - smallest I had, limited space. All lights work correctly on the bench, all connections good. The mystery: running forwards (power car leading), all is good, all lights on, will go anywhere. Put it in reverse, and it shorts out the entire layout. Take the trailer off and run the power car in reverse - no problems. Take the trailer car off and push it around in reverse- all lights on, no problems. Can even push the trailer car in either direction with another loco - no problems. Totally baffled. Have been all over both with multimeter and am as sure as I can be that there is no short. Both vehicles work independently just fine, but when together only in one direction. Clash of decoder settings? Any and all suggestions gratefully received! Thank you! Rich Ps Layout uses NCE Procab. Link to post Share on other sites More sharing options...
Nigelcliffe Posted June 22, 2017 Share Posted June 22, 2017 As per DM's post above, Is there any electrical connection between power car and trailer, of any form whatsoever ? Be it couplings (metal), buffers (metal), etc.. Something somewhere is connecting power in reverse between the cars. - Nigel Link to post Share on other sites More sharing options...
Tempfix Rich Papper Posted June 22, 2017 Author Tempfix Share Posted June 22, 2017 Nope, no connection between the cars. Was going to but the Bachman pickups proved good enough without. Standard Bachmann tension locks between them so nothing metal between the two. What has me baffled is that it works fine one way! Thanks for suggestions. Rich Link to post Share on other sites More sharing options...
Adrian Wintle Posted June 22, 2017 Share Posted June 22, 2017 From your description I'd be looking at whether the pushing of the trailer is causing something on the power car or the trailer to touch something it shouldn't. Try putting the power car on the layout and pushing against the coupling. Do the same with the trailer car. If they both work on their own and in pull mode then it has to be something mechanical occurring in act of pushing. Adrian Link to post Share on other sites More sharing options...
NIK Posted June 22, 2017 Share Posted June 22, 2017 Hello. I am hard wiring some DMU bits together and have got myself stuck. I'm afraid my level of knowledge with DCC is a bit pathetic. I am happy building things from scratch, adding pickups, lights, sound etc, but if after connecting all the same colour wires to each other it doesn't work, I don't really have a clue as to why. So I'm hoping someone out there can explain what on earth I've done wrong here. DMU. Power car is a Hornby (ex Lima) 101. I have added blue, yellow, white, green wires to the DCC socket and connected head and tail lights and internal lights. All work perfectly, run it all round the layout, both directions - no problems. It has a Hattons decoder. Trailer car is a conversion, but essentially a Lima chassis sitting on some spare Bachmann bogies I had so ready made good pickups. I have wired in the same head and tail lights and interior lights connected to a Hornby Sapphire chip - smallest I had, limited space. All lights work correctly on the bench, all connections good. The mystery: running forwards (power car leading), all is good, all lights on, will go anywhere. Put it in reverse, and it shorts out the entire layout. Take the trailer off and run the power car in reverse - no problems. Take the trailer car off and push it around in reverse- all lights on, no problems. Can even push the trailer car in either direction with another loco - no problems. Totally baffled. Have been all over both with multimeter and am as sure as I can be that there is no short. Both vehicles work independently just fine, but when together only in one direction. Clash of decoder settings? Any and all suggestions gratefully received! Thank you! Rich Ps Layout uses NCE Procab. Hi, what type of couplings do you have between the vehicles? - are they metal?. Regards Nick Link to post Share on other sites More sharing options...
Tempfix Rich Papper Posted June 22, 2017 Author Tempfix Share Posted June 22, 2017 Hi, what type of couplings do you have between the vehicles? - are they metal?. Regards Nick Standard Bachmann tension locks in NEM pockets - plastic. Rich Link to post Share on other sites More sharing options...
tamperman36 Posted June 22, 2017 Share Posted June 22, 2017 this may be a silly question but have you tried checking the voltage drawn by the motor when working in each direction whilst loaded and unloaded. Some chips cope better with voltage differences than others. Link to post Share on other sites More sharing options...
Tempfix Rich Papper Posted June 23, 2017 Author Tempfix Share Posted June 23, 2017 this may be a silly question but have you tried checking the voltage drawn by the motor when working in each direction whilst loaded and unloaded. Some chips cope better with voltage differences than others. Not really sure how to do that. I have a multimeter - would anyone mind clarifying? Thanks Rich Link to post Share on other sites More sharing options...
Tempfix Rich Papper Posted June 23, 2017 Author Tempfix Share Posted June 23, 2017 From your description I'd be looking at whether the pushing of the trailer is causing something on the power car or the trailer to touch something it shouldn't. Try putting the power car on the layout and pushing against the coupling. Do the same with the trailer car. If they both work on their own and in pull mode then it has to be something mechanical occurring in act of pushing. Adrian Can see the logic in this, but can't find anything untoward with either chassis - foreign objects etc, nothing on the pickups, no excessive bogie movement. But the real kicker is that the power car will push or pull anything else around the layout with no problem, and the trailer car will be pushed or pulled by anything else with no problem. Have been through both again this morning looking for shorts but could find none. Here is the latest brainteaser though: still convinced about the decoders not liking each other I reprogrammed the trailer car to a different number, then tried running them as a consist. It works forward fine, in reverse it works to speed step 4 - then shorts out! Really hurting my logic now! Thank you to all those which suggestions, won't get a chance to get in there until tonight now with small children awake but if anyone has any more ideas I'd be very happy. Thanks again Rich Link to post Share on other sites More sharing options...
Nigelcliffe Posted June 23, 2017 Share Posted June 23, 2017 Command station current may be an issue - Rich says he has an "NCE Pro-Cab". That is subject to some interpretation - do you mean "PowerCab", in which case current may be an issue as available current from a PowerCab is fairly low (depends on the power supply brick used). Or do you mean "PowerPro" system, in which case current will be vastly more than you need for a single 00 loco. Another test. Put the two halves of the DMU on the track, but not coupled. Run them, do they work ? If they do work, there is adequate power, and we're back to the short circuits somewhere within the mechanisms when the two halves are connected and running in one direction. - Nigel Link to post Share on other sites More sharing options...
Tempfix Rich Papper Posted June 23, 2017 Author Tempfix Share Posted June 23, 2017 Sorry, I do mean PowerPro - the 5A system. Large twin circuit layout - will happily run5/6 locos at once so don't think it is a power issue but may be wrong. I have the NCE circuit breaker too, set for about 4A (following blowing up a sound fitted A4 that derailed and bridged a set of points!). Had no issues with this - it just cuts the power in the event of a short. Will try testing them again tonight when the small ones have gone to bed. Thank you again for all ideas. Rich Link to post Share on other sites More sharing options...
NIK Posted June 23, 2017 Share Posted June 23, 2017 Sorry, I do mean PowerPro - the 5A system. Large twin circuit layout - will happily run5/6 locos at once so don't think it is a power issue but may be wrong. I have the NCE circuit breaker too, set for about 4A (following blowing up a sound fitted A4 that derailed and bridged a set of points!). Had no issues with this - it just cuts the power in the event of a short. Will try testing them again tonight when the small ones have gone to bed. Thank you again for all ideas. Rich Hi, Just a small chance the circuit breaker may be tripping out on one or both vehicles circuitry being temporarily disconnected from track due wheels lifting off track as loose coach starts to be pushed and then wheels reconnecting with track again. Do either of the vehicles have stay alive capacitors or sound capabilities?. Both stay alive capacitors and sound are known to sometimes be the cause of tripping of circuit breakers on DCC layouts. MERG produce a circuit breaker kit designed to avoid such inadvertent tripping. Regards Nick Link to post Share on other sites More sharing options...
Tempfix Rich Papper Posted June 23, 2017 Author Tempfix Share Posted June 23, 2017 Hi, Just a small chance the circuit breaker may be tripping out on one or both vehicles circuitry being temporarily disconnected from track due wheels lifting off track as loose coach starts to be pushed and then wheels reconnecting with track again. Do either of the vehicles have stay alive capacitors or sound capabilities?. Both stay alive capacitors and sound are known to sometimes be the cause of tripping of circuit breakers on DCC layouts. MERG produce a circuit breaker kit designed to avoid such inadvertent tripping. Regards Nick Hello. No sound or stay-alive. Track is flat with good weight to the chassis and has all wheel pickup as using a pair of Bachmann bogies. Am working through a process of elimination tonight. Have disconnected the lighting and the head and tail lights, all these work fine with another decoder in another unit. Third run with multimeter still found no faults or shorts. Have tried propelling it in both directions with a variety of other units - no issues. Have tried the motor coach with range other trailers and running in consist with other units - no issues there either. It must be something to do with how the Hornby chip reacts to the Hattons one. Unfortunately I only have the one Hattons one connected at the moment so can't compare. Think I may have to switch to see if that makes a difference - annoyingly I hard wired it in. Not letting this beat me! Thanks to all for suggestions, by all means keep them coming! Rich Link to post Share on other sites More sharing options...
28XX Posted June 23, 2017 Share Posted June 23, 2017 DCC. Just two wires. What could possibly go wrong. Link to post Share on other sites More sharing options...
Tempfix Rich Papper Posted June 26, 2017 Author Tempfix Share Posted June 26, 2017 Thank you to all those who have responded - I think I have cracked it. Having tried every combination of different DMU vehicles and run over it countless times with the multimeter I concluded that I would have to unwise the chip. Did so and put in a basic Bachmann one and it ran no problems. Put the errant Hornby chip in something else temporarily and same problem, it would only run one way if paired with a Hattons decoder, shorting out the layout when reversed. No idea why this should be, have tried a reset on both but to no effect. I now have a functional DMU but with a chip I can't hide so will have to invest in something a bit smaller. Thank you again for all the help. If anyone has suggestions of small but reliable chips I'd love some. Rich Link to post Share on other sites More sharing options...
johnb Posted June 26, 2017 Share Posted June 26, 2017 Thank you again for all the help. If anyone has suggestions of small but reliable chips I'd love some. Rich I've used a Digitrax DZ126 underneath an OO kit built 'Tin Hal' EMU, it is a pretty small chip. I did that because getting inside is difficult, it's tucked in between the equipment boxes on the underframe. It's held there with good old blutak and is not visible at normal viewing angles. I've used the EMU on my exhibition layout and it's fine, in fact it will be out this weekend running about. John Link to post Share on other sites More sharing options...
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