WTIU DCS Signal Quality Issues with Legacy Engines on Track

Patrick, I see the same issues. I like to run my Legacy engines in pairs in "train" mode. I can only have one Legacy engine on the track at a time with the WTIU. If I try a lash, it clicks on and off like there's a short. I read somewhere that if we want to run more than one Legacy engine we should address both engines the same # ID. I haven't tried that yet to see how the DCS signal is affected. Plan to this weekend. So far, for my experience, the WTIU has been a disappointment. I am contemplating putting my two 10 year old RevL TIU's back on and getting them "freshened up" by some forum members who repair them. Hope you find a combo that works. IF so, please share. I have been unsuccessful.

Mike

It's not uncommon for some Legacy locomotives to impact the DCS signal.  The cure is a 22uh inductor in series with the power pickups.  Obviously, this requires opening up the engine, so it's not a solution that everyone can do on their own.

Here's a list of suitable inductors for use internally in a single Legacy locomotive.

Legacy Locomotive DCS Protection Inductors

Mike,

I sort of glazed over my earlier issues, but they were somewhat similar.  I can't quite disentangle them, but I had a bunch of idle legacy/tmcc units on the track at first, and every time I would attempt to apply power, the WTIU would make a click and reboot itself.  Quite annoying when it takes as long as it does to boot.  Ammeter indicated about 2 amps in this configuration if everything was wired directly.  At the time I was using a ZW-L, and that induced a serious buzzing noise in the WTIU, I'm sure due to the gnarly wave form.  I tried a lot of things, but I'm pretty sure one of them was to have nothing else on the track and ZW-L power going through the WTIU.  With this, the engine would sit quietly (not going into conventional mode), but the WTIU couldn't recognize that anything was there.  As if communication was only working one way, TIU -> loco.  Needless to say, I'm pretty discouraged in the apparent lack of interoperability of the WTIU and Lionel power and command control locomotives.  I wish I had an old TIU for comparison.

John,

It isn't an exciting prospect to go through adding chokes to all the offending Lionel engines, but I do appreciate the suggestion and especially the pre-filtered link for parts.  I've got a batch on order.  I'll do some experimenting and report back my findings.  It is nice that MTH has the signal strength function.  Makes it pretty easy to test stuff like this assuming you can get the TIU and loco to talk to each other.

@Patrick Keistler posted:

John,

It isn't an exciting prospect to go through adding chokes to all the offending Lionel engines, but I do appreciate the suggestion and especially the pre-filtered link for parts.  I've got a batch on order.  I'll do some experimenting and report back my findings.  It is nice that MTH has the signal strength function.  Makes it pretty easy to test stuff like this assuming you can get the TIU and loco to talk to each other.

I'm sure that Lionel has never considered going out of their way to make the Legacy stuff more compatible with DCS, so if you're going to fix it, I suspect you'll have to do it.   I did this for a few of my Legacy locomotives that seemed to be the most troublesome.  The bummer is, for Legacy steam with the wireless drawbar, you have to add the inductor to the locomotive and tender.

Why would this situation be worse with the WTIU as compared to my old RevL TIU's.  Never experienced the signal issues with old ones. AND, I am using the Legacy signal booster, would that make it worse? Have been using the signal booster for many years.

Mike

Wanted to let the thread know of my experience last evening. I placed two legacy engines on the track set to two different ID#'s. WTIU clicked on and off and would not pass power to the tracks. I then reprogrammed the engines with same ID#, restarted them as one "engine" and not a "train". WITU passed power to track with no hiccups. 2 other DCS engines ran on other loops fed by same WTIU, no issues. Just my experience on my layout. I'm interested to see if anybody else has similar situation.

Mike

I can't imagine how changing the programming of the Legacy engines caused issue with the WTIU.

I'm going to give passive mode another try tonight, and see if I get the same behavior.  I'm still waiting on the 4 amp inductors so it gives me something to fiddle with.  I suppose I could put one of the 16 amp ones in an engine, but that seems a little ridiculous.

I wonder if the signal strength is somehow inversely correlated to the total power going through the WTIU.  I wish I hadn't converted all my passenger cars to LED.  That would have been an easy way to load it up without Legacy boards in the equation.

We are aware of intermittent issues with the ZWL power supply.  The waveform coming from this supply is not conventional AC.  The WTIU doesn't always interpret this as an AC waveform.  No surprise.  We are analyzing this now to see if we can make some firmware adjustments to accommodate this supply.

Here is a scope shot of the ZWL output. 

Here is a what 60Hz AC looks like. 

@Patrick Keistler posted:

Mike,

I sort of glazed over my earlier issues, but they were somewhat similar.  I can't quite disentangle them, but I had a bunch of idle legacy/tmcc units on the track at first, and every time I would attempt to apply power, the WTIU would make a click and reboot itself.  Quite annoying when it takes as long as it does to boot.  Ammeter indicated about 2 amps in this configuration if everything was wired directly.  At the time I was using a ZW-L, and that induced a serious buzzing noise in the WTIU, I'm sure due to the gnarly wave form.  I tried a lot of things, but I'm pretty sure one of them was to have nothing else on the track and ZW-L power going through the WTIU.  With this, the engine would sit quietly (not going into conventional mode), but the WTIU couldn't recognize that anything was there.  As if communication was only working one way, TIU -> loco.  Needless to say, I'm pretty discouraged in the apparent lack of interoperability of the WTIU and Lionel power and command control locomotives.  I wish I had an old TIU for comparison.

John,

It isn't an exciting prospect to go through adding chokes to all the offending Lionel engines, but I do appreciate the suggestion and especially the pre-filtered link for parts.  I've got a batch on order.  I'll do some experimenting and report back my findings.  It is nice that MTH has the signal strength function.  Makes it pretty easy to test stuff like this assuming you can get the TIU and loco to talk to each other.

I'm having the same or similar issues.  At first I thought I had an out of phase power lead, or even feeders to the track reversed, but everything checks out.  I have an inside loop with 036 to 048 curves mainly for semi-scale and short wheelbase engines and rolling stock. I have a couple of MTH engines running on that loop.  But when I try and combine Legacy and MTH on the big circuit, I've had various issues from the WTIU clicking and resetting, no signal to the MTH engines, and even turned the sound off of 2 of my newest MTH engines-I thought I'd blown soundboards, but got them back with a engine factory reset.  It really makes me want to put my MTH engines up for sale and just run Legacy.  I hope someone smarter than me here comes up with a better solution than adding circuitry to my Visionline 4014!  This stuff takes me back to Windows 3.1/486 PC nightmares back in the early 90's!

Frustrated to say the least!

Jim

@MTH RD posted:

We are aware of intermittent issues with the ZWL power supply.  The waveform coming from this supply is not conventional AC.  The WTIU doesn't always interpret this as an AC waveform.  No surprise.  We are analyzing this now to see if we can make some firmware adjustments to accommodate this supply.

Here is a scope shot of the ZWL output.

Here is a what 60Hz AC looks like.

Well this would explain quite a bit, since this is the transformer I am using.

Jim

@MTH RD posted:

We are aware of intermittent issues with the ZWL power supply.  The waveform coming from this supply is not conventional AC.  The WTIU doesn't always interpret this as an AC waveform.  No surprise.  We are analyzing this now to see if we can make some firmware adjustments to accommodate this supply.

Here is a scope shot of the ZWL output.

Here is a what 60Hz AC looks like.

It's nice to hear that there might be a solution for this power supply in the future.  I was about to start fishing for trades, but I would certainly rather keep and continue using it.

My original plan was to use the WTIU in passive mode and simply tag it onto the existing Lionel ZW-L based system.  I added the chokes and everything, but this didn't work at all.  I then tried running the power through the WTIU.  I wanted to keep conventional control through the Lionel system rather than MTH, so still sort of possible if I ran through the fixed channels.  This didn't work either.  Suspecting the above waveform was part of the issue, I sourced a PH180 and tried it out (power going through Fixed1 and Var1).  I had to concede to running conventional using the WTIU, which isn't all that bad honestly.  This brought me to the final issue here and the main topic of this thread.  Anything other than DCS on the track breaks DCS.

I'm continuing down the rabbit hole, but I really hope is isn't much deeper.

Again, I'm glad to hear that MTH is working on solutions.  I know this hardware probably represents quite an overhaul from the previous generation, but hopefully we can at least get back to baseline.

@MTH RD posted:

Here is a scope shot of the ZWL output.

Is that the ZW-L at full throttle?

@gunrunnerjohn posted:

Is that the ZW-L at full throttle?

I suspect not. Has anyone run a scope on the ZW-L at different voltages & under load? I was under the impression that a ZW-l at max voltage has a near-perfect sine wave.

@H1000 posted:

I suspect not. Has anyone run a scope on the ZW-L at different voltages & under load? I was under the impression that a ZW-l at max voltage has a near-perfect sine wave.

Me too, that's why I asked.

I basically burned out Fixed Channel 1 of the WTIU by innocently driving it with an 18 VAC chopped waveform from the MTH Z Controller. When the WTIU sees a chopped waveform, it gives off a worrisome and unexpected buzzing sound.  After about 4 seconds of this, Fixed Channel 1 is damaged and no longer able to send out the DCS control signal.

My other observation is when Base3 is attached to the ground and the 22uH choke is used (with pure sinewave transformer) , it takes a few more engine refreshes than usual on the DCS App to move the MTH engines from inactive to active. However, my MTH engines are still showing a signal quality of 10 while running Legacy.

@H1000 posted:

I suspect not. Has anyone run a scope on the ZW-L at different voltages & under load? I was under the impression that a ZW-l at max voltage has a near-perfect sine wave.

Hope someone can show this to be the case at all voltages. . . This "wave" form isn't even a wave.  Could this be a anomaly from the measurement introduced by the Oscilloscope?

Could the risk of damage be avoided by running the WTIU in "passive mode," i.e., connected to the track circuit but powered independently from its own brick?

I did some more testing tonight.  I didn't see any real differences between normal and passive mode, but I did make some new observations.

As before, if I take all legacy stuff off the track, pretty much everything works just fine with a couple of DCS engines running.  WTIU sees both of them no problem.  They both report good signal quality (8-10).  As I add legacy engines to the track, reported signal quality goes down, and will start to give a "no response" message.  With about 4 other Legacy engines on the track, it pretty much always shows "no response."

The interesting new observation is that everything still responds perfectly fine.  I can run the engine as normal.  The only time I got into trouble is if I ever hit the refresh button.  Then one or both engines would go into the inactive roster.  This leads me to believe that the signal coming out of the WTIU is probably loud and clear, while the return signal is attenuated in some way.  The result is a sometimes annoying, but manageable DCS+Legacy experience.

I'd love to hook a scope up to this and quantify what's going on, but that thing has eluded me for a couple of days now.  @gunrunnerjohn and @H1000, I have looked at the ZW-L output at full throttle in the past, and if I recall correctly, it still isn't perfect.  There is no jump, but there is still a short little flat spot between each positive and negative lobe.  Subjectively, the buzzing isn't as bad at full throttle, which makes sense.  Note that this could just be my particular ZW-L.  I feel like others haven't necessarily had this problem, and maybe it is supposed to be a perfect sine wave at full throttle.

I haven't found anywhere else online other than this thread from MTH that shows a scope view of the ZW-L output. I'm curious if it's similar to the ZW-C and how the C behaves with the WTIU.  One thing to try, before you turn on the ZW-L, turn the power up to max voltage on the handle feeding the WTIU. Wait for the WTIU to complete its boot up and then flip the switch on for the ZW-L. The transformer should instantly output max voltage like a brick power supply. The idea here is to avoid the slow progression of power increase from the ZW-L from 0 to 18 volts where the sine wave is modified until max voltage is achieved, the WTIU wouldn't see a modified sine wave from the ZW-L in this situation.

I've never been a fan of modified sine wave transformers, my preferences for power are the PH-180, Z4000, and the postwar ZW with proper circuit protection. I bought my dad a ZW-L a number of years ago due to it's classic look & feel but that's where its impressiveness ended. We didn't like the way it ran postwar stuff, everything seamed to have a louder buzzing and we also noticed a hum or buzz sound from some early TMCC & PS2 engines. The ZW-L was returned and the Z4000 went back into service on his layout.  It doesn't have the classic look but it is a solid transformer.