MTH DCS Headscratcher

Could you explain how everything is wired?

I see you just joined the forum today.  We don't answer questions from newbies!

Consider yourself hazed.

Welcome to our little world!   In all seriousness, it's definitely not due to the type of track.

As John asked, please provide specifics as to how you have everything wired.  If you're not sure, take and post pics.  Then we'll be able to better assist.

-Greg

Is it only PS2 engines that are not detectable, i.e., PS3 engines work fine  ?

@John Simanton posted:

The Inland Northwest Rail Museum was recently donated an O scale layout which has Gargraves track. It was strictly conventional control.  When we reassembled it, I attempted to install Digital Control.  Lionel TMCC works fine.  MTH DCS is unable to detect PS2 locomotives.  The DCS works fine with MTH track and with Lionel track, both modern roadbed type and old-fashioned tubular.  The only difference I can see is the use of Gargraves track.  Any Suggestions?  Thanks!

The outside rails are not connected to each other. could be an issue.

Don't know about PS3, we don't have any.

In your track test is one the layout (gargrave) and the MTH/Lionel small test sections?   There are things on the layout that can negatively effect DCS signal.  Certain lighted passenger cars with circuit boards, some Lionel engines, switches, etc....  Do a small loop test with gargrave.

Do search on the forum about DCS and you can learn more.  G

Search this forum for DCS wiring threads.  There's plenty of discussion on how to make it work and the starting point is MTH's "star" wiring recommendation.   Do DCS locos respond on any section of the track?

There are tons of things that can affect DCS signal strength on a layout.

I'd verify that the TIU in use is 100% functional and is putting out a full strength signal.

I'm with Greg, it's most definitely NOT the type of track, so that's not where you look.

We need to know a lot more, starting with the size of the layout, exactly how the power districts are wired, and how much track you have on one TIU output.  Also, if you're using more than one TIU channel, they must NOT be connected together or you'll surely have big issues running DCS locomotives.  Any track power accessories like signals, switches, etc. will likely need DCS isolation or to be moved to accessory power.

if you set up a test loop of any brand of track, break the center rail in at least one spot!

Is it possible the hot+ and common- are reversed somewhere?

@John Simanton posted:

The Inland Northwest Rail Museum was recently donated an O scale layout which has Gargraves track. It was strictly conventional control.  When we reassembled it, I attempted to install Digital Control.  Lionel TMCC works fine.  MTH DCS is unable to detect PS2 locomotives.  The DCS works fine with MTH track and with Lionel track, both modern roadbed type and old-fashioned tubular.  The only difference I can see is the use of Gargraves track.  Any Suggestions?  Thanks!

Layout has Gargraves track, but you tested with MTH track and tubular track. It's not the track. It's how the layout is wired.

Sorry it has taken so long to follow up, I went to the museum today to make sure I posted wiring info correctly.  According to the label on the TIU it s "REV I3."  Fixed Input 1 power is supplied by a Lionel PH1 Power Supply "brick."  Switching power source to postwar Lionel transformers or MTH transformers makes no difference, handheld remote still doesn't detect PS2 locomotives.  Lionel Trainmaster base is connected with through an MTH serial adapter to the TIU and a ground wire to the TIU 1 Fixed Output 1 connection.  TIU Fixed Output 1 is connected to the track by AWG 12 gauge wire soldered to the rails.  On the layout using the Lionel TMCC handheld remote, TMCC locomotives work fine.  On the layout, using MTH DCS handheld remote, a selected TMCC locomotive does not respond, but responds to the Lionel TMCC handheld remote.  Connecting the TIU to a short section of MTH Realtrax or a short section of Gargraves track both PS2 and TMCC locomotives work fine.  Still puzzled.

 Just a few questions.

 With a PS2 engine on the tracks. Does it come up silent and can you hear the watchdog signal in the engine ? If there is no DCS signal present. It should start up on it’s own.

 The fact that your TMCC runs fine with Cab 1. The DCS remote is just basically sending commands to the TMCC base. Nothing to do with weak track signal or DCS.  It should work with the proper cable. When you issue a command. Does the red light blink on the TMCC base ?

 When you mention hooking up short sections of track and everything being fine. Are you still using fixed one for this ?

What is the watchdog signal?  Afraid I am a bit ignorant.  With conventional power, I hear a click when power is first applied and PS2 starts up at about 8 volts.  Using the TMCC remote the red light blinks when a command is issued.  Using the DCS remote the red light blinks however the TMCC locomotive does not respond to all commands.  It doesn't respond to the thumbwheel throttle, the readout shows increased speed but the locomotive does not move.  But couplers fire, horn blows etc.  Regarding test tracks, are you asking if I am using fixed voltage?  Yes.

 The watchdog signal is a faint click like you would hear in a relay. It means it is seeing the DCS signal and will sit silent till you give it a command. If the engine is coming up with sounds. Are you using toggle switches to power up the tracks ?  This is normal if you are. It’s misses the signal and comes up in conventional mode when you flip the toggle on. Leave the toggles on and see if it comes up silent. Try moving it to another part of the layout. Or disconnect some of it and break it down into smaller sections. If the track signal is good. You should be able to hit Start Up even when it comes up in conventional and the engine will switch from conventional to DCS and you can run it with the remote. If the track signal is that bad it will constantly miss the signal. You really need to describe the layout and how it’s wired.

 Are you using Fixed 1 voltage to power any turnouts ? This will ruin the signal.

 As far as your TMCC problem. By any chance would the engine be K-Line with factory cruise ? I remember the same issue. It was a matter of changing the speed steps. I have a couple of engines I could try to duplicate it on.

Remove all lighted cars from the layout and only have 1 locomotive on the layout. This is a starting point. Some non-MTH locomotives can disrupt (short out) the DCS signal. I suggest that you concentrate on getting DCS working before you concern yourself with running TMCC with MTH remote. Place the MTH locomotive on track that is close to where the TIU connects.

Layout is on a rectangle approximately 8' x 28' Right now it has two concentric ovals of Gargraves flex track, approximately O-84 and O-72.  There are two sets of crossover switches but the center rails are isolated so electrically it is two seperate tracks.  Right now the switches are manually thrown.  We are only running single locomotives until we can get DCS going or we give up.  Outer oval is about 70' of track, inner about 64'.  Each oval has a DPDT switch for selecting conventional (MTH Z-4000) or digital (DCS/TMCC) power.  Power is wired to the track at several points and it basic center rail hot/outer rails common.  Covid has delayed opening the museum for 2020, we are trying to be able to at least run trains when we do - a lot of work remains.

 Sounds like each loop should be on it’s own channel. Like fixed one and two.  If it has buss wiring it shouldn’t be a problem. I’ve found DCS is more forgiving than it’s given credit for. But. On a layout this size. A 12 gauge buss with 14 gauge feeders and you should be fine. 

 I haven’t seen it. There were issues early on with some toggle switches degrading the DCS signal. If you can bypass them I would for testing. 

I agree with Dave, put each loop on it's own DCS channel, you may find things get a lot better.