New to DCS operations (and the 0 Gauge Forum).  Layout size, 41 x 27, 4 mainlines with crossovers and double slip switches laid with Atlas track and growing. Outer main insulated from inner 3 and separated into 5 blocks with 3 feeds each, all switches jumped around.  Inner mains all electrically connected due to the double slip switches.  TIU (not revision L, but upgraded to 6.1) with TMCC concurrent.  TMCC runs fine everywhere.
Outer main blocks temporarily wired together by jumping at a terminal board, mains 2 and 3 fed at multiple places by a ring bus, main 4 to be star fed.  PS2 and PS3 engines will not detect to load even after isolating to one loop with 5 block feeds.  Only way to get an engine to detect is to use a short jumper from the TIU to a programing track.   Even after isolating outer main to one block with 3 feeds and 14 feet of wire from TIU to terminal board, engines would not detect.
Once loaded from a program track fed by a short jumper, select the engine on the remote and it would state “Engine not on track” but the engine would take certain commands and run anyway.  Buttons on the left of the TIU seem to work OK, but right side didn’t.  All remote functions work fine on program track.
Do I have a bad TIU?  Bad wiring?  previous temporary  wiring with 2 mains and 1 single feed, all electrically connected worked fine.
Power wiring is not problem for me, but signal wiring is a different story.  A friend with some DCS experience and a much smaller track is just as puzzled.
I have the DCS companion book on order.  I needed to ask the experts, as I know there have to be layouts bigger than this running DCS.
Gray Lackey
Original Post


Your wiring is suspect. Further, I had some difficulty understanding exactly how you're wired.

I suggest that you use a simple star wiring method: with center rail-isolated track blocks that have one and only one connection to a TIU channel, via a terminal block.

The DCS Companion 3rd Edition and The DCS WiFi Companion 2nd Edition both have detailed, illustrated discussions of how to use star wiring effectively.

DCS Book CoverThis and a whole lot more about DCS is all in MTH’s “The DCS Companion 3rd Edition!"

This book is available from many fine OGR advertisers and forum sponsors, or as an eBook or a printed book at MTH's web store!

DCS Book Cover

This and a whole lot more about DCS WiFi is all in MTH’s “The DCS WiFi Companion 2nd Edition!"

This book is available from many fine OGR advertisers and forum sponsors, or as an eBook or a printed book at MTH's web store!

Thanks Barry

Books are due in 4-4.  Luckily nothing is secured permanently yet as far as wiring.  Looks like I have some reading to do.


David Minarik posted:


It also sounds like you have more than one feed to your blocks.


As Dave mentions a wiring diagram would be helpful to reference to your post.


It definitely sounds like you have not wired your layout correctly, as David indicated it sounds like you have more than one drop per block, and the rest is a little confusing.  The best way to wire your DCS is using the star pattern, with no more than 10-13 Track joins per each block.   If you are eventually going to run Legacy put a drop on the opposite outside rail and another on the outboard Black DCS Channels as you wire your layout.


Last edited by Pine Creek Railroad

Will have to look on the TIU.  It is not a "revision L" unit.

Yes, I had more than one feed to an insulated block daisey chain fed. 

Disconnected all track and redid two blocks completely isolated form each other (both rails) with one feed each to each block and was still experiencing the "engine not on track" message.  Atlas switches to be electrically jumped around as to not have to depend on internal electrical switch conductors (I know there have been problems with older switches).

Quick hand drawn diagram attached


Your diagram only has 1 DCS block /loop wired.

Are your blocks isolated by the center rail?

Each block must have 1 feed.

Last edited by David Minarik

After trouble, I was just trying the outer loop, the diagram is one loop showing all three rails.  I have all rails isolated at the blocks in order to run a conventional or DCS unit by means of a DPDT switch eventually.  Currently everything is tied together at a terminal for just DCS.

When you have some older untested equipment, it can be better to test it without the layout when you encounter problems.

I would try connecting it to a short piece of track with just one engine on it. I would also add a light bulb or one of Susan's filters with older TIUs.

When you connect it back to the layout, do it one section at a time to try and isolate the issue.

Last edited by Engineer-Joe

The TIU works fine with short jumpers to a 40in section for programming.  Locomotives work fine on that short section after programming.

Power source is the right side of a MTH Z4000 set at 18 volts.

I have seen some talk of light bulbs to "tune" the signal.  Please advise on the filters you mention.

Are blocks completely isolated or just center rail isolated from each other?  if insulators are required, I would think even a small loop could have problems.

Books are due in tomorrow, looks like I have a lot of reading vs the manual that comes with the TIU.  At least I have a great source to ask questions to, that is a tremendous asset.


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