Adding A Block Shorts Entire Layout

Everything looks fine to me in your diagrams so the only thing I can think of is on the actual layout in Block 6 you have two wires reversed or you possibly have a bad switch among the 10 switches in Block 6.

Just curious as to why you decided to have so many blocks on what seems like a smaller sized layout? Obviously, you are running TMCC which should negate the use of not all but a lot of blocks. Or at least that’s what I thought.

Trouble shoot.  One wire at a time, One track connection, One switch.  You may have to dis-assemble.  Use the 1/2 method.  Split the track block in half.  The short should be in one, or the other section.  Continue the 1/2 method, and again, and again. Shorts are usually easier to find than an open circuit.  IMO.  Mike CT

A good VOM.   Volt Ohm Meter is helpful.

It most likely is not your wiring but the track.  Do you have a meter?  See it your block is completely isolated as expected. 

What type of track are you using?  New or used?  If used are you sure you got all the old wires off?  Did you cut any track and there is a little spur still making contact?  It does not take much to get power to short out? 

If that block 6 introduces another transformer source, check for it being in phase with the present sources.

Thanks to all for your advice.  I was able to find the short by the 1/2 method.  It turns out that a feeder hot wire came out of a female spade connector and was causing a short.  Block 6 is up and running now with all switches operating.  Several of them need to be tweaked to prevent derailments.  The quality control of the current fastrack switches is very poor.  I find that one out of every three need "repairs".  Most of my feeder wires are connected with .110 connectors.  I soldered smaller sections that do not have the spade connectors underneath where I want power drops.  If I had it to do over, I would solder all connections as the spade connectors will come off.

Oh, I will be running mostly TMCC; but I have a small fleet of conventional engines that I will run as well.  The blocks, nonetheless do make trouble shooting easier and allow turning off a siding with lighted cars.  I'm not sure I have the best arrangement for conventional operation, but the blocks I set up should allow flexibility in the conventional environment for my needs.

@Richard Whipkey posted:

  Most of my feeder wires are connected with .110 connectors.  I soldered smaller sections that do not have the spade connectors underneath where I want power drops.  If I had it to do over, I would solder all connections as the spade connectors will come off.

I soldered 14 GA feeders directly to the tabs underneath fastrack.

The layout is going on 15 years old and I've never had a voltage issue.