Update: Problem returns- Surprising solution to erratic TMCC performance!

Hey Rick,  I also have a layout under construction i.e., building the bench work now... and should have it done with a couple of rudimentary loops for testing in about 7 to 10 days.  I too have a ZW-L as well as varying locomotive power... conventional, TMCC and Legacy.  I'm marking your post so that when I begin testing I can reference for similarities and or differences.

My thread is  First layout in 25 years... O guage (some scale).

Rock On

dennis

Well, in command mode the ZW-L has 200 speed steps just like a Legacy locomotive.  I'm not sure what the resolution is in conventional mode with the handles, but I'm guessing it's probably a lot less.

If I read your post correctly, you were running command engines with the ZW-L set to conventional and when you switched it to command mode, things straightened out? I'm not clear as to what solution you discovered.

TMCC in command mode has 32 speed steps, the ZW-L in command mode has 200 speed steps.  I'm thinking he noticed how smooth the TMCC locomotive was running in conventional mode with 200 speed steps.

FWIW, I put the ERR AC Commander in my first generation Phantom locomotive that I added a second Pulmore motor to.  The difference in smoothness and low speed performance was remarkable over the old LCRU2 that it came with originally.  I attributed it to the difference between the TMCC 32 speed steps and the ERR AC Commander 100 speed steps.

Improving the Lionel Phantom Locomotive

In conventional mode, the ZW-L chops the sine wave.  The LCRU and other early TMCC decoders also chop the sine wave.  So there's a risk that the wave gets diced so small as to be insufficient.  It could also be that Legacy locos convert the incoming AC to DC and filter it, so they're not as susceptible to this phenomenon.  An oscilloscope on the transformer output, and also on the decoder outputs would tell the whole story.

The ZW-L handles the voltage variation exactly the same as far as output whether it's being controlled by the handles or by the TMCC/Legacy command system.  The actual output is always a sawtooth waveform for voltages less than maximum.  The issue is how many speed steps are attainable between the two methods of inputting the desired output voltage, I don't really know that.

Dennis-LaRock- Good luck on your layout! Looks like you have a great space for it. 

GVDobbler- I discovered the solution to my erratic TMCC loco performance using my CAB-2 and ZW-L. With the ZW-L in conventional mode and the voltage set to 18V, performance was horrible, as I described in my initial post. Switching the ZW-L to command mode, via the switch on the back of the transformer, cleared up all the issues I described, and things are still working great.

GRJ- Not sure if the difference in speed steps would account for the dramatic difference I've seen, but I'm no electronics wiz! Could that difference be what was causing the surging and jerky running even when no throttle inputs were being given? I mean, these locos were running like they hadn't been serviced in 50yrs, and were running on filthy track with dirty wheels. A flip of the switch to command mode and they are all running smooth and as quiet as can be expected.

Truthfully, without actually looking over what is going on and exactly how things are configured, I'm only guessing as to what is happening.

Well, time to eat some humble pie, as bad luck would have it, the solution was short lived. It seems that it was not as simple as switching from conventional to command on the back of the ZW-L. The jerky, erratic running came back again! This time, nothing I tried seemed to help, so I swapped out the ZW-L for my trusty MRC Dual Power transformer. After making the swap, after several power cycles, and testing with more than a few locomotives, everything runs smoother than ever without the ZW-L. I am more than a little disappointed by this, as I really like the ZW-L, and planned to use it to power most of my layout. Has anyone else experienced these symptoms with the ZW-L? Is there a problem with my ZW-L? Any insight would be appreciated.

How do you have the signal wire from the legacy base wired? Directly from the base to the outside rail or to the U post on the transformer? Is it possible when you flipped the switch your moving the wires? I would run one of your TMCC engines around and start wiggling wires and see if anything changes.

Doug

Doug- Thanks for the input! I've tried with the signal wire attached to the "extra" common post on the back, attached to the U post of throttle D, and directly attached to the track, all with the same result- jerky, erratic behavior. All connections were secure. As I'm writing this, I realize I haven't tried powering the track with anything but throttle D, on the ZW-L. I wonder if I have one output acting up.

Yes, a good technique in troubleshooting is to substitute ONE thing at a time, until the problem improves or goes away.  Different transformer, different Legacy base (if you have one, or can borrow one from a friend), different CAB-2, etc.  You already said that multiple locomotives are affected, so in this case it's probably not the loco.  Don't give up!

You might consider configuring the ZW-L for conventional only operation and then just running with TMCC with the transformer remote control out of the picture.  Also, you should certainly try the other outputs of the transformer!

All right, I’ve tried the other throttle outputs on the ZW-L and got the same result in both command and conventional modes, with the TMCC signal wire on the base post or U post of the throttle being used. Things seemed to run OK for a while, then they would begin jerking and surging, and acting crazy. 

If another transformer runs them 100%, you're down to either the ZW-L or something about the way it's wired.  Time to take it to another layout and see if it screws up there.

Thanks, GRJ, I’m using common bus wiring, with feeders every 6’ or so. Only one main line operational at the time. I laid out a couple pieces of Gargraves and hooked everything up directly to the independent stretch of track and saw the same result. I’m really starting to think there is something wrong with the ZW-L outputs, but I sure don’t know what it could be.

The thing that gets me is you say your Legacy engines run fine and it's only the TMCC engines that have the problem. Did you try holding your hand over the engine when it acts up? 

Doug

Doug, yes, the Legacy locos appear to run OK. I don’t know if it’s the way the Legacy locos filter power (if they do), or if it’s as John says, something to do with the speed steps(?). I haven’t tried putting my hand over any of the locos. What might that do? 
BTW- I’ve switched back to my MRC Pure Power Dual and things have been running wonderful. Smoother than they ever did with the ZW-L.

If an engine is having trouble receiving the signal the lights flicker and the engine can run erratic by putting your hand above the engine it helps it receive the signal from the track.

I'm sure someone can explain it better than me.

Doug 

@ricka1 posted:

Doug, yes, the Legacy locos appear to run OK. I don’t know if it’s the way the Legacy locos filter power (if they do), or if it’s as John says, something to do with the speed steps(?). I haven’t tried putting my hand over any of the locos. What might that do? 
BTW- I’ve switched back to my MRC Pure Power Dual and things have been running wonderful. Smoother than they ever did with the ZW-L.

A video for Doug?

I stand by my original theory.  With the ZW-L, the sine wave is getting chopped twice.  Depending on how the wave is being chopped, there may not be much of it left, and the loco is starved for power.  Or, it interprets the incoming peak voltage as the average voltage causing erratic operation.  An oscilloscope, especially on the motor leads, would tell the whole tale.

My experience with TMCC and even Odyssey locos, was that they ran very poorly in conventional mode.  My $.02.

@Ted S posted:

I stand by my original theory.  With the ZW-L, the sine wave is getting chopped twice. 

For running with TMCC, the ZW-L should be at full throttle, so that doesn't really apply.

@gunrunnerjohn posted:

For running with TMCC, the ZW-L should be at full throttle, so that doesn't really apply.

John, would there be any issues running TMCC with the ZW-L at less than full throttle? I believe I was running it close to full, with the handle set to provide 18V according to the built in meter. I think I was getting 18V measured at the track with that setting.

While this is very odd and confusing I can say last time I hooked my oscilloscope to the ZW-L even at full throttle the sign wave is still chopped. With a standard volt meter I’ve always gotten about 16VAC and would need a true RMS meter to read 18VAC at full power Still don’t understand how this is only affecting TMCC operation. Have you tried any conventional locomotives with AC pull-more motors?

Zachariah, yes, I have a number of conventional locos from prewar to conventional classics and they all run great, absolutely no problems. By the way, I really enjoy your videos on YouTube! 

Conventional locos with AC Pullmor motors will run just fine on chopped-wave AC.  In fact they will run slower especially when starting, smoke better, and their headlights will be brighter than they would be on a postwar ZW.  The downside is that the motors, e-units, etc., are noisier.  Some operators object to the "buzz" or growl that comes with chopped-wave power.  I think the noise is a worthwhile trade-off for the extra performance, but to each his own.

The Pullmor is a universal motor.  That means it will run on AC or DC.  In fact, when you run one on DC it is dead quiet!

@BobbyD posted:

A video Doug?

Bobby,I'm not having the problem and I was just throwing some ideas out there.

Doug

@ricka1 posted:

John, would there be any issues running TMCC with the ZW-L at less than full throttle? I believe I was running it close to full, with the handle set to provide 18V according to the built in meter. I think I was getting 18V measured at the track with that setting.

Truthfully, I've never seen any issue running TMCC/Legacy at half throttle on other chopped-wave transformers, they just have a lower top speed.  I'd be pretty surprised if the throttle setting is the issue.

@zhubl posted:

While this is very odd and confusing I can say last time I hooked my oscilloscope to the ZW-L even at full throttle the sign wave is still chopped.

Like I said, I don't have a ZW-L, but other chopped waveform transformers do have some distortion of the sine wave at full throttle, perfectly normal.  I'd be surprised if the ZW-L looked much different.

CW-80 Full Throttle 2A load

MTH Z-1000 Full Throttle 2A load

MTH Z-1000 Full Throttle 8A load

@trnluvr posted:

Bobby,I'm not having the problem and I was just throwing some ideas out there.

Doug

Yep, answered on phone and dropped out "for" 🙂 

Would like to see a video of his issues.

I did a scope test just like @gunrunnerjohn did, but with a CW-80 and a Legacy PowerMaster. The PowerMaster did not further distort the incoming chopped wave - it simply cut it shorter appropriately for the throttle setting. I also noticed that the PowerMaster throttle setting was consistent. If I set the CW-80 to 100% power, and the PowerMaster to 60%, and then adjusted the CW-80 down, the PowerMaster didn't change (until the CW-80 essentially dropped the input below the PowerMaster output).

As soon as I get a chance, I’ll try to get a decent video of the problem. I’ve switched back to my old MRC Pure Power Dual transformer and things are smooth and trouble free at the moment. I’ll need to switch back to the ZW-L before I can get a video. Stay tuned!

A motor, flywheel, drive train, etc., has mechanical hysteresis.  If you cut the wave short enough, pretty soon all you'll get is heat and no movement at all.  Throw in a fairly coarse closed-loop speed control that tries to acheive a target speed based on the (sensed) input voltage, and you have all the ingredients for a funky electronic barbecue!

My other favorite toy growing up was Hot Wheels cars.  The cars were fun but the real play value came from the orange plastic track.  I still remember what they said at the end of their TV commercials: "Some cars not for use with some sets."  Words to live by!!

First video is without command base hooked up, ZW-L in conventional mode.

Now this was in command mode. It’s hard to see but if you listen, you can here the stuttering and jerking as the loco moves along. It is much more apparent in person.

I switched to the old MRC Pure Power Dual and I've seen zero issues with anything I run on the layout. TMCC, Legacy, ERR, and conventional all run perfectly. Could I have a problem with the ZW-L? Seems like a big waste of money if I have to relegate this state-of-the-art, flagship transformer to running accessories, lights, and uncouplers on my layout! Has anyone else had problems with their ZW-L? Is there any recourse if the unit is malfunctioning?

Of course, Lionel service should be able to make it right.