Rev. 13B TIU

Whatever problems the Legacy engines are having, it's extremely unlikely that the TIU, or any other aspect of DCS, has anything to do with it.

To the best of my knowledge, there has never been a documented incident of DCS ever negatively affecting a Legacy or TMCC engine.

However, if your uncle has the "one wire" from the Legacy command base connected to a Common input (black terminal) of a TIU channel rather than to an output black terminal or directly to the track outside rail, passing the Legacy signal through a DCS signal generator could have unpredictable results.

Further, be aware that the 4 channels of all TIUs, except for the original Rev. G, are not connected internally. Therefore, connecting the Legacy "one wire" to one TIU channel's Common will not necessarily distribute the Legacy signal to all the tracks connected to all 4 TIU channels.

This and a whole lot more is all in “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 OGR’s web store!

Alright, not sure why disconnecting the TIU fixes the problem then. Both Remote and TIU are on version 5.0 Legacy is on version 1.53 

Is it wired correctly.  Barry gave you a reason why it could be an issue?  G

I have the legacy wires (4 of them) connected to a terminal block and connected directly to the Z4000s that power the track. The upper level tracks are fine, it's just the bottom level tracks that are the issue. Moving the wire to the output side of the TIU doesn't care anything. Seriously, disconnecting the TIU fixes the problem, why I'm not sure but it works without the TIU in play. 

I have the legacy wires (4 of them) connected to a terminal block and connected directly to the Z4000s that power the track.

That sends the Legacy signal through the DCS signal generators - not a good idea.