DCS Repeating Sounds

Weak track signal.  If you have a Rev. L TIU, there's a driver chip that is prone to transient damage. 

Hmmm not sure, so you’re saying I need a new unit then?  Fantastic...

I have MTH engines that do this on a random basis. No rhyme or reason as to when it happens.  I have a full 10 track signal, and if an engine happens to do the feature repeat, usually the first time I blow the whistle, it won't do the repeat the rest of the time I am running it.

I get repeat sounds in some sections.  But that’s because I didn’t isolate all my blocks and the loco gets the DCS signal from two power drops.

With wiring that doesn't properly deal with the DCS signal, you can get reflections and double or triple commands.  It's a track signal issue, it's just a question of where the issue is coming from.

@RON ARNDT 091718 posted:

I have MTH engines that do this on a random basis. No rhyme or reason as to when it happens.  I have a full 10 track signal, and if an engine happens to do the feature repeat, usually the first time I blow the whistle, it won't do the repeat the rest of the time I am running it.

I've experienced similar (or at least closer to this than the 80% rate of occurrence cited by the OP). 

But I also do not have everything properly blocked for DCS, I'm running on a loop on carpet central, so there can be signal multi-path issues.  (my track signal regularly goes south as a train gets to the opposite side of the loop from the point where the TIU is hooked to the track).

I might have seen it a few times on a less random basis on an engine or 2 sitting in one place  (close to the TIU connection point) as well when I cycle through all the sounds while sitting still.  I've had one particular sound repeat regularly when others do not.  It's infrequent enough that I wrote it off as not critical (or a function of my less than optimal carpet central setup).

-Dave

How many TIUs on your layout?  If more than one, does the doubletoot go away when you turn all off but one?  I had discussed doubletoot with MTH R&D some years ago.  They had no solution, other than possible induction between parallel conductors.  For many years I only had it occur in one area, and then of a sudden it appeared throughout the layout.  Signal strengths, as reported by the locos, are all 9-10.

@DJ Haney posted:

...I even asked MTH a few years back and they didn’t really know why. 

Wow. I'm not sure who you asked that wouldn't know this issue? It's mainly from the same remote command signal arriving to the engine from two directions.

If you have more than one track power feeder in the same block, this can/will happen.

So, to review, the first step in trying to resolve your issue is to divide your track into as many separate blocks as the number of power/dcs feeds you now have going to the track - with a feed going to the approximate center of each block and see if that solves the problem. 

Assuming you have your existing feeds now spaced about equally around your track, you shouldn't have to relocate any feeds. Just cut the track about equally on each side of each feed so that everything is equally spaced out. 

Joe, that is clear.  But why?  I have 70 blocks, each fed with one hot lead & iventer rail insulated from adjoining blocks.  My recollection, last time I dug around, is that when I turned off the second TIU, it stopped happening. Multimeter tests show infinite resistance between center rails in different zones, when no cars on track.

The only connection between the TIUs' hots would be through in-car/loco connections between hot and grounds--i.e., hot on TIU #1 to in-car bulb, through bulb to outside rail, along outside rail to another zone, from outside rail through bulb to inside rail.

Happens on PS3 only. Not on PS2. Software oversite? It is annoying. Most of my newer PS3 diesels do it.

That has occurred since the early versions (I can't believe DCS has been around for close to 20 years already). Basically, if you have more than one feed per block, the command pulse is going to come in from multiple places and if they're far enough apart, the locomotive will see both of them as separate commands. The rule of thumb is ONE feed per block. One risk from multiple feeds in a block is that the signal can cancel itself out.  There's some debate as to the maximum length a block can be, but that probably depends more on how electrically sound the track joint connections are, how clean the track is, and the electrical resistance of the rail itself.

SIRT: Wrong.  Happens with PS2 also.

Matt: I have one feed per block. All 70 blocks toggle switched.  No cross-feeds.

@Richie C. posted:

So, to review, the first step in trying to resolve your issue is to divide your track into as many separate blocks as the number of power/dcs feeds you now have going to the track - with a feed going to the approximate center of each block and see if that solves the problem. 

Assuming you have your existing feeds now spaced about equally around your track, you shouldn't have to relocate any feeds. Just cut the track about equally on each side of each feed so that everything is equally spaced out. 

I moved any connections on my layout so that they are near the ends of each block. I did that way back before the TIU version L was released. I had a filter/bulb at the other end of each block. After getting version L TIUs, I removed the bulbs and or filters.

 It would seem better for power distribution to wire towards the center of each block. I had less signal issues (nearly none) with the connections at the ends as Barry B recommended to me.

Remember though, I run mainly 2 rail. There isn't a perfect way to wire every layout. I go at a layout with the tools of what I've learned. I stay flexible so that I can adapt to issues that may arise.

 I'm in the school of what works is OK. I have my basic right way list, and I adapt to what occurs as I move forward.