DCS/TPC 400 Setup - Power Backfeed Into TIU?

Stop doing it the hard way- just run passive. This is also valid for the new WTIU.

All you need is a 22uH choke, rated for the amperage on each power source channel. Shown is an example for one channel but the concept is valid for doing the same thing up to all 4 channels.

The choke coil blocks off the high frequency DCS signal from being shorted by your transformer source (in your question, a TPC400). The TIU or WTIU then is only providing the DCS signal. The track gets the combination of the 2, power from the source and DCS signal from the WTIU.

The new WTIU comes with a power supply already to power it. The older TIU did not have a supply shipped, so it was suggested to provide one.

@Tidewater Jake posted:

Hello, All!

It’s been a while since I’ve posted on this forum, and I wanted to reach out regarding a hypothetical DCS question as I’m helping my Dad witch his layout.

So in summary, we want to have some conventional control on the inner loop of the layout (there are two loops total).  Currently, it all is powered through 2 Lionel 180 Watt bricks, which input into the 2 fixed channels of our DCS TIU.  We also have a base 3 currently set up. Now, we’ve heard that the variable channels on the DCS can be sub-optimal when it comes to conventional control.  Therefore, we want to install a TPC 400 we own to control the inner loop conventionally.

My idea for the wiring was to install a switch that would shunt the hot & ground to either the TIU fixed channel 2 (same as it currently is), or to the TPC 400 based on whether we want to run command or conventional. We’d probably do the same setup if we ever wanted run the outside loop conventional (the TIU will be powered by the wall plug), it’d just require another switch and TPC 400/Legacy Powermaster.

Now, my question is this:  will the power from the TPC 400 cause any backfeed issues with the TIU, given that the fixed channel leads will still be connected between the layout and the TIU?Yes, if you just connect the TPC 400 to the OUTPUT channel of the TIU- you effectively short out the DCS signal. However, if you add a choke in series on the hot leg (not common or U) of the TPC- now you can run passive mode.

I’d hate to get this all wired up, only to fry the TIU or cause signal damage with this setup.- Again, just run passive mode- others already went this route with other Lionel power sources like the ZW-L- effectively a powermaster- the same as a TPC.

Thanks for any input you can provide, and I appreciate your time!

Previous discussion and now a few early adopters of the WTIU are using passive mode.

https://ogrforum.com/topic/mth...-so-far-non-dcs-user

Yes, you can have passive mode, DCS signal, TMCC/Legacy signal from a base (base3) all at the same time. Base 3 simply connects to common- common being common- well all the tracks are in common with common right........ The passive chokes are in the power supply side- just after the TPC or transformer.

Previous discussion contains choke suggestions for passive mode https://ogrforum.com/topic/pas...-tvs-recommendations

@Vernon Barry posted:

Previous discussion and now a few early adopters of the WTIU are using passive mode.

https://ogrforum.com/topic/mth...-so-far-non-dcs-user

Yes, you can have passive mode, DCS signal, TMCC/Legacy signal from a base (base3) all at the same time. Base 3 simply connects to common- common being common- well all the tracks are in common with common right........ The passive chokes are in the power supply side- just after the TPC or transformer.

Previous discussion contains choke suggestions for passive mode https://ogrforum.com/topic/pas...-tvs-recommendations

Understood, thanks for the advice!

Just to be clear on what I was considering, I was thinking of putting the toggle before the TIU, so that the power would be re-directed away to the TPC 400, and no DCS signal at all would be produced.  My curiosity was regarding whether the power from the TPC coming back in through the (still connected) fixed output wires would cause any issues with the TIU, which may or may not be on depending on what I’m running on the other loop.

With this setup, I wouldn’t have to crank up the TPC 400 to run DCS - I just make sure the switch is on “Command” to the TIU & grab’n’go with the DCS remote.

I’ll definitely review that passive mode information you sent over!  I’ve heard a bit about it, and I’m looking forward to diving into the technical side!  Thank you again for your time!