Apollo 13 suffered from a main B Bus undervolt resulting from an explosion. my layout used to just have a single bus but now I do have two one for Track power and on for accessories. However I did get a couple of shorts after some redesign work and that took a long time to find so here’s the sorry saga of how not to wire up your layout and what I did to fix it, which I hope you'll find useful

As I say, I now have a dual bus setup and if there is a short on the track  it trips the Z21 booster, not the z21 controller which mean I can still through points etc. Also unlike the tired old RailMaster controller the Z21 resets itself as soon as the trip is fixed so I spend less time crawling around the layout to test fixes.  I should add  just have the one bus as my layout only has 70m of track 40 points, and I'll never run more then 4-5 locos simultaneously as I have no automatic control. However I and others who adopt this approach get a lot of flak, partly because it can be hard to diagnose shorts (you can't make this up can you), etc.

Originally I when I just had the one bus  I used the bus wiring connectors from DCC Concepts to attach dropper wires and wiring to my points to the bus:

Frankly I always found these connectors a pain to use -

• I am rubbish at soldering and I found it hard to get a good joint from these to the bus which occasionally meant something didn't work
• I need to add a lot of these to the bus and that means breaking into the bus again and again.

What really got me thinking about this was that I needed to add my equivalent of a fiddle yard (which isn't really as it's on show)  and the trackwork to go around my awesome new ADM Turntable (the subject of another post). I wondered if there was a better way to wire up the new track points and turntable to my bus which looked tidier and was easy to understand. On the DCC Concepts forum I noticed my good friend Bunkerbarge using a different sort of connector (from CM3 models) to attach lots of droppers to his track.   These gizmos allow up to 9 feeds to be connected via one of these blocks which in turn is connected to the bus and it has screw in terminals which meant less soldering👍  

So I ordered a load of them and proceeded to rewire my whole bus using these new CM3 connectors and here's that some part of the layout again with just the one bus

Having done all of this when I turned on my Z21 I got a short, but how to find it?  With these new connector blocks all I needed to do was disconnect the feed wires from each these connector blocks to the bus in turn until there was no short.  It did not take me too long to realise that I hadn't used insulating joiners for the middle route on a three way point.

  The second was much harder. Something weird was going on around a particular point in another siding and whenever I connected track to it.  My senior moment was that I forgot to properly reconfigure this Peco Electrofrog point - I hadn't removed the bridging wires connecting the frog to the point blades under the point though I had electrically connected  the point blades to the outer rails. 

This all took me longer than it should have because I did not do what I would do at work when making changes to designs.  I mention this because I work in software engineering at Microsoft and despite what you may think 😃, we spend much more time testing our work than we do writing new code. So if I had done proper testing when re-wiring I would have gotten my answers much more quickly. Specifically

Regression Test  - is everything OK before a change is made? Not doing this means that you have no idea if a change you make is the problem or if it was there already.

Unit Test - Test what you have changed -  Does the change you just made work? For example is that siding you just added working OK?

Integration Test - Test the whole system again. It might be that you have introduced a problem somewhere else and not realised.

However you wire up your layout, add decoders to trains, put in signalling and lighting these principles should help you particular if you are collaborating on a large layout.

Footnote: since writing this I have moved on to loco detection (and here's how my layout is now wired up) and now my track is isolated into 5 zones each powered by a separate Digikiejs DC5088RC  detection module and so I can quickly establish where a fault is and then dig into the specific section