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Debugging DCC bus short


choralc

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Well some good news I think. This morning after completely isolating the outer oval and joining it up with new RJs I ran a GWR 0-6-0PT and thinking I've possibly wrecked two points I still thought it was nice to see it crawling around. 

 

So with renewed enthusiasm the unsoldering of some droppers from the tags began on the one half where the sidings are. I then tested where the Elite connectors join the bus and 0.L was the result. I then connected the Elite and the startup sequence completed.

 

Bear in mind the outer oval is disconnected from everything else so I will now rejoin the outer oval to the bus one set of droppers at a time and test as I go.

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I have found an obvious fault. When I tested it I could see why! Perhaps you may remember I could see all of the sidings droppers bar one?

 

Yep.

 

Thank you all for the encouragement. I will put the track back together now and then reconnect the droppers that I unsoldered. And of course testing as I go along just to make sure another fault wasn't hiding somewhere else.

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Well done indeed. I have followed this thread with interest as the same thing happend to me when I built my layout nearly three years ago. Despite everyone saying there was a fault in my wiring I was convinced that there wasn't. It is frustrating to have to go throught the whole layout - so the "halve it" method is very useful to know. Glad it is sorted for you. Wonder what the next issue will be? :-)  R-

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I don't understand TWD.  As both halves of the layout would still be connected to the bus, is it enough just to put a break in the track?

 

 

  You are right Stephen if indeed the bus is a continuous length with a single feed to the controller. I was thinking of it as 2 buses joined at the controller. If first method, you would have to divide the bus in two. Thank you for pointing out my error.

 

Good news seems that Choralc has found the fault.

 

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The only way I could physically halve the layout, as indeed there is one continuous bus with the control connectors joined to a tag approximately in the middle, was to remove points in the track work thus separating the layout into thirds. Then removing the droppers in the correct third was a bonus.

 

Being an oval I did a quick eyeball to put one colour closer to the edge of the layout and was careful to remember which rail was which but apparently when I rotated the board to finish the sidings I became disoriented on one pair (eyes firmly fixed on the ground in shame and embarrassment)!

 

I was going to finish resoldering the third I had taken off but when the good lady arrived home and I showed her I had found a fault - and hopefully the fault - and had the 0-6-0 go around she began to paint the white areas as those surfaces were in need of sealing.

 

So tomorrow I will finish soldering and fit three Lenz and two Hornby accessory decoders.

 

Thanks again everyone.

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On the next layout you build, check for continuity across the rails as you attach each feed. ;-)

You can also split the layout into power districts, with switches, so that if there's a fault it's easily found. :-)

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Glad to see choralc found the problem.

Yes TWD, I'm afraid I did assume that the bus was continuous and hadn't considered any other way to do it.  Now, though, I think it's a good idea to split the layout into power districts, as poliss has put it.  Of course, I also intend to adopt the 'test as you go' approach suggested by others on this thread.

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Even if you only have a smallish layout the idea of splitting it into switchable power districts for fault finding purposes is excellent. Something I shall adopt on my next build.

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