Really weird problems from my MTH PS3 Diesel...

I’ve had the “repeated” command issue with many of my ps3 locos.  It always goes away after i put a second engine on the track or change the track/wire length.  I think it’s related to signal strength and/or reflections.

Try this: remove one piece of track or otherwise break the continuity of the loop and then retry the commands that were repeating.

Don't discount the possibility that the derailment affected the TIU.  If you have a Rev. L TIU, they do have a propensity to take damage to the DCS signal driver with voltage spikes.  The result is a loss of signal strength.  Oddly enough, the symptoms you suggest sound just like poor DCS signals.   It's quite possible one or more other engines are just a bit more sensitive to the DCS signal and don't display the same symptoms.

Rplst8....I was going to try that next to see if the weirdness disappears.

GRJ....Yeah.....I was afraid of that. Is there some diagnostics I can do to determine the issue is TIU related and not engine related?

FYI.....I've been running this engine for well over a year without any issues....until the derailment that is.

Well, most of us fall back on the TIU signal tester to see what the TIU output signal looks like.

Design of a $10-20 DCS-TIU Port Tester Tool?

Yes...I did buy that kit....still in the shipping pouch. This project just jumped to the head of the list!

Do recall the link to that whole discussion thread? I seem to recall the instructions for using the tester were "in flux".

Or maybe you have those instructions for doing the test handy?

The instructions are pretty easy, but read the thread as you have to calibrate it as well.  I cheat and use my 'scope, but there's a "quick-n-dirty" method that Stan came up with.

The other thing to note is you must use a pure sine wave transformer in the testing.  That's most any brick or post-war transformer, but NOT something like the ZW-C with the bricks, ZW-L, or any of the MTH Z-xxx controllers with the brick.  You can use the brick from everything but the ZW-L (no brick), but not the front-end voltage controller.

I use PW ZW's as power supplies so no problem with pure sine wave AC.

Yaaaaa....the TIU Signal Tester is assembled (Thank You GRJ for your thoughts on soldering the voltage regulator...worked like a charm)!

I took a lead from another post by mounting the circuit board in a pill bottle with the leads threaded through a hole drilled in the cap and a hole drilled in the side for the potentiometer. It all worked out great!

Now....to test my TIU!

Remember, it has to be calibrated before it'll accurately test anything.

Yep....I watched your (?) video on how best to calibrate the tester.

BTW....I'm running 18V into the TIU channels. That shouldn't be a problem for the Tester when it's plugged into the OUTPUT channel....correct? And all outputs should be disconnected from the track while testing one channel?

@Junior posted:

Yep....I watched your (?) video on how best to calibrate the tester.

BTW....I'm running 18V into the TIU channels. That shouldn't be a problem for the Tester when it's plugged into the OUTPUT channel....correct?

I’ll let others field this, but I think thats OK.

And all outputs should be disconnected from the track while testing one channel?

Yes.  The transformer (in) and tester (out) are the only two things that should be connected.

The double or ’ghost’ command is a common thing with DCS.   MTH doesn’t even know why it happens.  

One theory suggests that the command signal from the TIU does not get shut off in time before the confirmation from the engine back to the TIU is received.  

If your track signal is ok, I would not worry about it.  

The tester runs fine on any normal track voltage.  However, note that it only works with a pure sine wave transformer, a chopped waveform fools it in to thinking there's a DCS signal where there isn't.  This is strictly a function of making something for a few dollars in parts vs a few hundred dollars.

With a pure sine wave on the input to the channel of the TIU, it works great.  For variable channels, they should be either in fixed mode or turned all the way up to full output voltage.

What I do to test with the tester is as follows.

1. Make sure the remote has at least one DCS engine loaded.
2. Set the remote operating mode to "Speed".
3. Configure the variable channels to "Fixed" mode.
4. Jumper all the input channels together and connect them to a pure sine wave transformer.
5. Plug the tester into a channel, and hit "Start Up" for the engine in the remote.
6. Check the status of the signal on the tester LED indicators
7. Repeat steps 4 & 5 for each channel.

Hi David....

Thanks for the info. It's just odd that the "ghost" commands have never occurred on this engine (or any other engine) before; until after the derailment.

I've been meaning to assemble the TIU Tester anyway. This situation just "lit the proverbial fire..." to get that done.

Hey GRJ....

Thanks for the follow up and the testing procedure. Question on Step 4 - "Jumper all input channels together." In my configuration I have each channel powered by its own PW ZW. It's this config acceptable or just go with the the channel jumpering using one ZW?

Hi rplst8....Thanks for info. I'm always afraid of doing a "smoke test" by supplying too much power.

@Junior posted:

Thanks for the info. It's just odd that the "ghost" commands have never occurred on this engine (or any other engine) before; until after the derailment.

Ghost commands are common with a weak signal.

Sometimes not always

That's what the word "common" means.   We see ghost commands all the time on the club layout, we're still working on rewiring to correct DCS issues.

Since DCS really uses the track as an RF transmission line, a standing wave reflection can also cause ghost commands.

I've got 10s everywhere on my layout but in one area that crosses 2 switches locomotives will double commands (i.e. playing two crossing signals back to back when the SXS key is pressed once) depending on locomotive speed. It probably has something to do with speed and how many electrical connections (jumpers between rails on Ross switches) there are in that area.

@gunrunnerjohn posted:

That's what the word "common" means.   We see ghost commands all the time on the club layout, we're still working on rewiring to correct DCS issues.

Since DCS really uses the track as an RF transmission line, a standing wave reflection can also cause ghost commands.

Sometimes that perfect 10 signal will still not eliminate the ghost signal.   I hope it cures it for you.

I agree Dave, it's not directly related to the signal strength.  Since the measured signal strength for DCS is simply the number of packets out of 10 properly transferred, that really doesn't tell you about the actual signal, but rather how lucky you are in dodging the issues in signal transmission.