andy_tidball Posted July 10, 2016 Share Posted July 10, 2016 I am new to all this so apologies if this is in the wrong place. I have a Hornby 2-6-0 James which i put a hornby digital decoder. the loco ran well on 12v but on digital it would run quite happily and then all of a sudden jump into reverse. I took the chip out ran it again on analogue (runs nicely). I have subsequently installed a new chip and a 104 capacitor. It seems to run nicely but again is now jumping into reverse. It seems to be on a articulate point each time but doesnt seem too consistent and is doing it on two layouts.Summary:one locotwo deferent new chipstwo different layouts both running lenz digital systems. how do I fix this? Andy Link to comment Share on other sites More sharing options...
Flashbang Posted July 10, 2016 Share Posted July 10, 2016 Hi Sudden reversing or taking off at high speed which is uncontrollable is caused by the decoder receiving poor data. It then 'sees' the 15volts on the rails, thinks its full power DC and allows the locos motor to run at full power in whichever direction the decoder had received the poor data. To overcome this initially ensure all rail tops and loco wheels and any rear of wheel wipers are spotless clean. But the very best way to stop the run aways occurring is to turn off DC operation in the decoder. This is carried out by reducing the value stored in CV29 by four. So if currently its at a value of 6 make it 2. However, this can only be carried out on a DCC system that allows CVs to be altered. The Hornby Select cannot do this. The Elite and Elink are able to undertake this. Your Lenz system should be able to alter CV values. Link to comment Share on other sites More sharing options...
Chrissaf Posted July 10, 2016 Share Posted July 10, 2016 I have subsequently installed a new chip and a 104 capacitor..If the capacitor has 104 printed on it, then the value is 0.1uF which would infer that it is a motor suppression capacitor. If this capacitor is on the wheel pickup side of the decoder, remove it. It will be affecting the ability of the decoder to interpret the DCC signals correctly and potentially cause the issues you are observing. Link to comment Share on other sites More sharing options...
poliss Posted July 10, 2016 Share Posted July 10, 2016 You mean it jumps into reverse when going of the points? If so, then one wheel is touching both rails as it's going over the V of the points causing a short circuit. Link to comment Share on other sites More sharing options...
Fishmanoz Posted July 10, 2016 Share Posted July 10, 2016 Further to Chris's, remove the capacitor, full stop, not needed. Decoders contain correctly designed suppression. Link to comment Share on other sites More sharing options...
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