TMCC locomotives not functioning on specific track loop

Did you break up the continuity of the connection to the outside track you have the command base connected to?  Like, is one switch not transferring the signal through it.  Jumper a wire over with alligator clips - outside rail with command base connected to it to an outside rail in the dead loop.  See if it makes a difference.  A five minute check.  If it does, run a permanent jumper under the layout.

On second thought, both outside rails would have to isolated to cause the problem.  I would try it anyway.  You never know sometimes with this stuff.  Good luck.

RBR,

   If you are running DCS also, run the Legacy to both the outside opposite Rail and the all the Black out channels of your DCS.  This increases the Legacy signal using both outside rails of your track, it works great for me, I give Marty F all the credit for advising me to set up in this way with my Legacy.  Also make sure you are not running a multi plug with your Legacy, some multi plugs are not grounding the Legacy Base correctly, messing up the Legacy signal.

PCRR/Dave

 Check the center rail insulation everywhere. When you have run for a while, feel rail for heat, that's a tell-tale.

 My thought is an intermediate(active when weighted), or micro short (close enough for larger "sparks of power" to "jump" the gap). The loco draw keeps the majority of power flowing properly, never shorting fully enough, or long enough, to ever trip the breaker.

 Intermediate, and "gap" shorts, have a tendency to throw an offset into the ac wave too (which = a dc wave, which= whistles). 

 Broken wire(internally within insulation) can do this (dc) as well as connections (esp. where dis-similar metals connect and/or corrode.(like rusty pins on tubular, or aluminum connectors on steel/brass)

 I could also see the serial signal getting interfered with should this be the case.

  On the simple side sure, and I'm no command expert, but worth a look till better answers roll in.

  I've had similar issues running tmcc (& pw) in conventional.

  

 Also, newer Weavers only like one type of whistle control for sure. I thought it was "old school" pure sine wave, but I could have it backwards, they might like chopped.(the few I had? great creepers!)

 Are your track & wheels really clean? Dirty track & wheels can sound electronics randomly all day.

 

 Semi-related FYI, I have a mix of transformer & train brands/types ranging from pre-war to the 90's. The whistles/horns/bells, all act up differently depending on which transformer is used on which train. An AF 18b no whistle transformer is fine on PW, but modern sounds lose their minds on that unit (non-stop party time). My 4 1033's wont operate half the tmcc trains w/sounds. My new power units, wont operate PW trains well enough to "blow" any at all.

 

      

What kind of track?   I like the alligator clip(s) idea.

The track is Atlas-O, with the loop having a couple switches used to cross over to an outer loop which is having no problems. Power supplies are Z-4000s, and DCS is also on the track. Just this one loop out of six having the problem... Legacy seems fine, just TMCC having the issue. Even went back to the original TMCC controller with no luck.

 

I'll try some of the additional wiring suggested here tonight and post back with results...

OK, found the problem - the DCS TIU is interfering on the track signal, which is on one of the variable channels... No problem when I bypassed the TIU...

 

Onward to more troubleshooting...

 

Thanks for the replies!