WarwickLaken Posted October 3, 2020 Share Posted October 3, 2020 I have just finished wiring all my droppers onto the two bus wires. I have not put power to the track yet but found a short between the two rail lines. I corrected the dropper mistakes and soldered them to the bus wires. I have checked and double checked the polarity of the droppers to the bus and they are correct, yet wherever i measure the resistance between the two rails I get a resistance of 110 ohms.All my track and points are Hornby and as yet have not fitted the point clips.I would appreciate any thoughts an the problem.Thank you Link to comment Share on other sites More sharing options...
Rog RJ Posted October 3, 2020 Share Posted October 3, 2020 Have you got the bus wires connected back to the controller yet? Point clips aren't needed if you are using bus wires and droppers. Link to comment Share on other sites More sharing options...
WarwickLaken Posted October 3, 2020 Author Share Posted October 3, 2020 Hi Rog, I have not conneced the bus wires to anything yet. I dont want to connect as I believe there is a short Link to comment Share on other sites More sharing options...
Howbi Posted October 3, 2020 Share Posted October 3, 2020 Might be worth disconnecting your turn-table then check again..........HB Link to comment Share on other sites More sharing options...
WarwickLaken Posted October 3, 2020 Author Share Posted October 3, 2020 The turntable is not connected as yet. Link to comment Share on other sites More sharing options...
WarwickLaken Posted October 3, 2020 Author Share Posted October 3, 2020 I feel a bit of a numpty? after days of searching for a short, Howbiman mentioned my turntable. That prompted me to think and the roundhouse model my father built. Inside were two trains. Trains off the track and no short circuits.Im still new to this!!!! Link to comment Share on other sites More sharing options...
Howbi Posted October 3, 2020 Share Posted October 3, 2020 Glad it sorted, thanks for the feedback..........HB Link to comment Share on other sites More sharing options...
Fishmanoz Posted October 3, 2020 Share Posted October 3, 2020 You weren't measuring a short, rather the decoder resistance in the locos. Link to comment Share on other sites More sharing options...
96RAF Posted October 4, 2020 Share Posted October 4, 2020 When wiring a bus I use a battery and buzzer clipped across the rails which indicates any short as soon as I create one. In my latest bus wiring I used commercial bus terminal blocks each with a power indicator. This indicator led and resistor was enough to trigger the buzzer, short or no short, hence the decoder resistance as Fishy said will give a similar indication of a short. You were fortunate that when soldering bus wires you didn’t create feed back and damage your decoders, as some soldering irons do not have the tip earthed and you can get stray voltage on track. Link to comment Share on other sites More sharing options...
Chrissaf Posted October 4, 2020 Share Posted October 4, 2020 I'm not so sure the locos in question have had decoders fitted yet**. Whenever I have measured the resistance across the decoder red and black wires (track wires) I have observed a resistance reading of about 30,000 ohms give or take as you are measuring the resistance of the input 'bridge rectifier'. Of course there might be something else in the loco also across the wheel pickups in addition to a decoder that will shunt the decoder resistance. Note** They might still be 'DCC Ready' locos awaiting conversion. Or locos originally belonging to his father he mentions. Note to 'WarwickLaken', just be aware that locos marked on their boxes as 'DCC Ready' are DC Analogue locos and not Digital DCC compliant until such time as the 'DC Bypass' plug is removed from the internal DCC decoder socket and replaced with a 'plug in' DCC decoder. It would not be the first time a 'self stated' newbie has mistaken 'DCC Ready' locos for being 'DCC Fitted' ones. Link to comment Share on other sites More sharing options...
Fishmanoz Posted October 4, 2020 Share Posted October 4, 2020 If as Chris says the locos aren't DCC fitted, it would be the motor resistance you are measuring. Link to comment Share on other sites More sharing options...
Chrissaf Posted October 5, 2020 Share Posted October 5, 2020 For which 100 Ohms as stated by the OP would be an appropriate value to read for motors. This is the reason why I put forward my 'what if' theory in my previous post. Link to comment Share on other sites More sharing options...
WarwickLaken Posted October 5, 2020 Author Share Posted October 5, 2020 Thanks for all the useful advice, the buzzer idea could have saved me an awful lot of time rewireing the droppers. I only have one dcc ready train as yet and it is safely still unboxed, I do have a lot of decoders to fit to my trains so will be more than likely back here again when I make mistakes. Link to comment Share on other sites More sharing options...
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