sam496 Posted December 27, 2019 Share Posted December 27, 2019 hello all, must be 12 months since I was last on here, I have recently removed a DCC module from a Merchant navy class loco form an orient express dcc set. replacing it with a hornby TTS chip, a very tight fit in the loco so I extended the speaker wires and put that in the tender.Every thing works as it should apart from the direction of travel, I have to select reverse to go forward and forward for reverse, as it replaces the original DDC chip I think it must be something to do with the decoder? Any help apprciated Sam Link to comment Share on other sites More sharing options...
Chrissaf Posted December 27, 2019 Share Posted December 27, 2019 Assuming that you use a controller that allows you to read & write CVs..Read the value of CV29..If the read value is an odd number, take 1 away from that number and write the resultant value to CV29If the read value is an even number, add 1 to that number and write that new resultant value to CV29 instead..If you have a controller that cannot read & write CVs then physically reverse the wires soldered to the motor. Soldering iron and soldering skills required..How to Solder tutorial. Link to comment Share on other sites More sharing options...
sam496 Posted December 27, 2019 Author Share Posted December 27, 2019 I have both types of controllers, I checked CV 29 and it was at 255 which it would not accept 254 as being out of range, however I set my pointer and the drop down box appeared saying values between 0-48 were valid with 6 being the default. I downloaded 6 to the decoder and it still went the wrong way, I then changed it to 5 and downloaded that. Everything is fine now thanks for the help. Link to comment Share on other sites More sharing options...
Chrissaf Posted December 27, 2019 Share Posted December 27, 2019 5 is not a good value value for CV29 ..... see comment below..If you had loaded a value of 6 and the loco went the wrong way.....you should have changed it to 7 not 5. If you read my original post again...I said 'add 1' if the value of CV29 is 'even'..A value of 5, means that you have disabled 128 speed steps and changed it to 14 speed steps which is now an obsolete feature. Fortunately for you, your loco is a 'steam loco', because disabling 128 speed steps usually also disables 'directional lighting'..A value of 255, just means that the controller could not detect the decoder in that particular instance..On-line CV29 Calculator Link to comment Share on other sites More sharing options...
96RAF Posted December 27, 2019 Share Posted December 27, 2019 TTS decoders need 128 speed steps set to work properly according to the blurb. Link to comment Share on other sites More sharing options...
sam496 Posted December 27, 2019 Author Share Posted December 27, 2019 I will change it back to 7 in the morning.. thanks for the feedback. Link to comment Share on other sites More sharing options...
Fishmanoz Posted December 27, 2019 Share Posted December 27, 2019 I would suggest you change to 3 instead of 7. This way you have reverse direction (1) and 128 speed steps (2) but you've turned off DC running (4) which is the default for TTS decoders. Link to comment Share on other sites More sharing options...
sam496 Posted December 28, 2019 Author Share Posted December 28, 2019 Changed back to 7 all seems to be working ok. would have reported sooner but I've up to neck in baseboard making for a layout that I have had Planned for some time.L shaped with a 6x6 square at each end joined by two 10x2 atraight runs. Link to comment Share on other sites More sharing options...
96RAF Posted December 28, 2019 Share Posted December 28, 2019 Value 7 gets you this - i.e. with DC ops turned on, not recommended. Go with Fishy’s suggestion.To use this tool live go to http://www.2mm.org.uk/articles/cv29%20calculator.htm/media/tinymce_upload/c8f10dd309f71efd413cecc4005b52d2.png Link to comment Share on other sites More sharing options...
dlaloum Posted January 3, 2020 Share Posted January 3, 2020 Possibly a silly question, but why are people averse to having dc capability enabled? Link to comment Share on other sites More sharing options...
Chrissaf Posted January 3, 2020 Share Posted January 3, 2020 Because on a DCC layout, if the decoder loses synchronisation** with the track DCC signal. This it can do very easily when traversing dirty track or insulfrog points and other poor track conditions. The decoder can switch itself into 'DC Analogue' mode. Now since the DCC track signal is at full voltage. The loco takes off like a rocket at full speed and becomes completely uncontrollable and the only option to stop it, is to shut down the track power..This is called 'DC Runaway'. This unwanted phenomenon can be eliminated by turning off 'DC Operation' support in CV29. Sometimes, a brief transient 'short' of the loco on the track will trigger 'DC Runaway' as well, because the 'short' disrupts the DCC track signal transmission. In the case of a loco induced 'short' it may not necessarily be the loco that caused the short that exhibits 'DC Runaway'. All or any of the decoders on the layout can be affected as they are all 'listening**' to the DCC signal..Note**In DCC, the decoder constantly listens to the DCC signal and needs to keep synchronised with it. It has to listen to ALL the DCC digital signal packets just in case one of them is addressed to the listening decoder and requires an action to be performed by it. Therefore 'data signal synchronisation' is a very important part of DCC control systems.. Link to comment Share on other sites More sharing options...
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