Striking signal difference for PS3 vs. PS2 locomotives--common experience?

All I can say is that any of them can be weak. Different reasons could be the culprits, like dirty wheels or rollers.

If you have the version L and felt like testing, try removing the filters at these points. I removed mine from tracks on the L version TIUs. This engine just maybe more sensitive and you can use it as a base to test with. Then when it works well, the others definitely will.

 I have a few random engines like this one. I think some have needed batteries replaced now? I've lost track of most. Seems like many problems went away now. They pop back up every year after the summer season of running outside.

 Keep a close tab on this engine's battery health. If it keeps being a problem and the only one, maybe swap out the battery.

Thanks.  PS2 has a BCR2, no battery.  BCR2 is working as expected.  Can always chase cleaner track, but that’s pretty recently done and wouldn’t explain great signal for PS3.  I was curious about the contrast, and looking for comments from others who may have been able to compare in this way, with performance as well as signal measurements, side by side same day, same place on layout, PS2 vs PS3.

I've got PS2 3V stuff with BCRs and PS3. Haven't noticed a difference between the two types with TMCC on or a TMCC locomotive powered up at the same time a DCS locomotive is on the track.

Probably related to large, complex track plan, significant wire runs, exaggerating the difference.  Likely it will be others with similar challenges who see this difference, if they are reading this.  Maybe the strength of my TMCC signal with ground plane wires and (minimum) gain from DM booster is part of the reason for the contrast, too. That may spread the measured DCS signal difference.

My tentative conclusion for myself is that it may be worth the trouble to convert important locos to PS3 to make operation fun and not work.  A strong TMCC signal proved crucial to making that system work smoothly, and it hums now in the farthest reaches of the railroad, so I’m not giving that up to get PS2 to work.  I recall from a video narrator’s comments that Bob Bartizek chose to not bother with DCS or with Legacy’s shorter wavelength and range remote signal on his large layout, and only uses original TMCC because it is just easier and more trouble-free.  That’s a bit larger, but a similar situation.

The C&NW Lines has a few important trains to model whose best loco choice is an MTH model in the stable, so those may have to be converted to PS3.  Keeps us off the street.

How does it change if you remove the TMCC buffer from the equation?  Maybe it's time to start narrowing down possibilities.  How about checking the DCS signal strength on the TIU?  Have you invested in one of the little signal strength checkers?  This allows you to verify that each of your channels is still putting out the full strength DCS signal.

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

With a REV L TIU, using Susan Deats's capacitor/resistor signal improvers, will actually degrade the DCS signal (at least on my layout).  There should be no reason to use them with a REV L TIU or the magic bulb trick.  Try removing them and see what happens.

Found this thread, seems my answers may lie in some parts of its discussion of circuits to add:

https://ogrforum.ogaugerr.com/...=lastReply#lastReply

Two quick questions:

Is there a theory to support putting a choke in series with the TMCC booster output (in between final output and track) to filter stray frequencies that interfere with DCS signal?

For a beginner with scopes who likes to have good test capability, what is a scope that is not too difficult to learn to use?  (That rare thing, good technical writing in the instructions, would be one key element)  I would like to be able to measure the signal voltage and quality of those DCS 'Packets' anywhere in the system from TIU output to places on the track with problems.  For instance: The question of whether to remove Susan Deats' filters with my Rev L TIUs would be much easier for me to resolve with measurements, rather than just qualitative impressions of change.

Thanks

cnwdon posted:

Two quick questions:

Is there a theory to support putting a choke in series with the TMCC booster output (in between final output and track) to filter stray frequencies that interfere with DCS signal?

The short answer is no.

cnwdon posted:

For a beginner with scopes who likes to have good test capability, what is a scope that is not too difficult to learn to use?  (That rare thing, good technical writing in the instructions, would be one key element)  I would like to be able to measure the signal voltage and quality of those DCS 'Packets' anywhere in the system from TIU output to places on the track with problems.  For instance: The question of whether to remove Susan Deats' filters with my Rev L TIUs would be much easier for me to resolve with measurements, rather than just qualitative impressions of change.

Thanks

 In general, most of the common 'scopes are pretty similar in operation, so I don't think you'll find one that's vastly easier to use than another in the $200-400 price range. 

As for how difficult it is to learn, as someone that's been using them for well over 50 years, I'm probably not qualified to answer that question.  Obviously, walking up to a new 'scope isn't that daunting an experience for me, but for someone that has never used one, it's a different matter.  Another factor is how familiar you are with what you're trying to accomplish with the 'scope.  It's not just the tool, but it's understanding the job you wish to accomplish with the tool.

Thanks 

What to measure? What is pertinent to actual DCS performance. Is that just signal amplitude (volts) or are other aspects of tracing valuable information? Steep end of learning curve here 😕 Seeing the waveform would make me happy, but knowing what to look for in it is also needed.

A steer toward a scope from mfr known for good writing in their instructions would be gratefully received too!

Perhaps can post some interesting results then. The threads that include what large club layout experts have added are fascinating.

Adrian! made this Telemetry Train Car, he posted details in the linked thread. He used this to help sort out DCS problems with the large layout at his train club. Unlike the TIU tester, this can be run around the track and provide DCS signal readings, but it's also a bit more expensive. Making it might be a little difficult, but Adrian! has a link to the parts and programming code. If you had some questions, I imagine he would try to help out. It might be similar in cost to a scope, but I was thinking it might also be easier to use once it's up and running? 

I recently bought a scope, had never used one before and it is a bit difficult for a beginner to get started. I still have a lot of learning to do with electronics in general.  As GRJ says above, it's also about knowing what you are looking at that's probably as (or more) important than being able to properly connect it.  So far, I can muddle through the connections, but I am not always sure what the scope is actually telling me?  Anyway, I got a Hantek DSO5102P, 100MHz for about $225, but I don't think the manual meets your definition above. Youtube videos might be a better option for learning than the manual? 

RTR, thanks.  I’ve just been reading that scope’s instructions pdf online, and it is not the worst translated English I’ve seen, for sure.  I see there are help menus on the scope itself.  Do you have comments on the quality of the help on the scope?  The fact there is talk about Windows-type logic seems promising for a daily Windows user.

I read Adrian’s calculation of the DCS signal frequency range, and gather a range of about 3-12 MHz is needed.  I assume this scope’s 70 MHz range would cover 0-70, and serve for DCS, right?

In the manual, there is the choice of “Equivalent acquisition” as an option for periodic signals.  This looks like it would apply to the signal “packet” design of DCS.  Curious if I’m starting to get how the scope would work in our area of interest.

Finally (keeping this as non-random as I can manage), any comment on what besides amplitude (signal voltage) would be of interest in the tracing?  My intent here relates to trying small experiments, like removing one of the Susan Deats filters and seeing change in scope tracing, or removing a Zener diode spike absorber, or a Scott’s Odds-n-Ends spike absorber, or the DM TMCC booster, etc. Some of that involves getting into awkward positions under the layout with an aging back, so multiple repeat performances can ruin a day—need to learn as much as possible from each trial.  I don’t expect any of those will show dramatic results alone, so knowing what to look for as “improved” signal after a change is important.  Seeing a train operate and finding the DCS remote reading of signal strength is then the final gross test of validity.  Being a diagnostician by profession, going back and forth from test result to patient condition is my cognitive style.  Assuming there are interesting results, I hope to post them here, including scope screens if they merit sharing.

As always, thanks to all for the shared wisdom and experience.

Separate issue: Going back to other threads, noting GRJ’s proposed TVS suppression board for addition to a TIU internally. Avoidance of “stray capacitance” from TVS component mentioned.  I’ve had TVS Zener diodes with 37v threshold across input and output terminals, both, of my TIU for some time, thinking they will protect from spikes coming in from either side.  Seeing that is obviously NOT the solution chosen by GRJ, it must be too simple (-minded?).  I just don’t understand the why at this point 

You have a 3mhz signal and you're driving it into a significant capacitance.  Let's say you're TVS has a capacitance of around 1,500pf, which is about what the commonly recommended 1500W 33.3V TVS at Digikey exhibits.  That presents a load of 35 ohms of capacitive reactance across the DCS signal at the 3mhz signal frequency.  That is a significant load for the drivers to overcome.  Put a few more around the track, and the problem gets worse.

The TIU has a TVS protection diode in each output channel already, so there's little need for one there.  One across the input won't hurt anything, the DCS signal is injected past the input and is already isolated from the input transformers by an RF choke.

That was the issue I was addressing with the extra diodes on my protection board.

Cool.  At least one simple thing I can do, will remove Zeners from output side and retest that PS2 engine for laughs. Thanks!

The DSO5102P is 100MHz, which, as I understand things, is good for anything we might be doing with our trains. They also have a 70 MHz (DSO5072P about $200) and a 200 MHz (DSO5202P about $300) in the same 5000P series. As far as I know they are the same except for the different bandwidths. Maybe someone more knowledgeable can comment on the best specific bandwidth needed for measuring the DCS signals. 

I'll defer actual functions and their proper uses/usage to GRJ, Adrian! and the others here that are much more knowledgeable with scopes than I am. Still learning myself and will be learning something here as well.

As for the help, it definitely has a lot of listings in the index, which is alphabetical. I believe it might be a bit better than the manual? Looks to be more detailed than the manual anyway. Punctuation is not good, but other than that it's still readable. The English itself is on par with the manual and it all makes sense.  

Just went to look for "Equivalent acquisition" you mentioned above and found no reference to it in 'built-in' help. At least not anywhere I expected it to be anyway. It's not under Data Acquisition as it is in the manual and there's no Equivalent or "Equivalent acquisition" in the index. Only found 'Sample', 'Peak Detect' and 'Average' in the 'built-in' help. However, pressing 'Acquire' (button on the scope) does have a 'Real Time' or 'Equ Time' setting where you can select either one of these modes. 

There is a 'Help' button on the scope that brings up a menu for the built-in help. From there you can select Index, Topic, Prev Page, Next Page, or Exit. It's also 'context sensitive'. When you select a function or setting on the scope, then press the 'Help' button it takes you to the related info for what you have selected. After I selected the 'Real Time' / 'Equ Time' setting, pressing 'Help' brings up the same 'Sample', 'Peak Detect' and 'Average' descriptions I found in the Index. 

Much of the use of any electronic test equipment starts with knowing what you're trying to measure and understanding what you see when the measurements don't come out as you expect.   Sometimes when you see a great 'scope picture, you don't realize that to get that perfect picture could have taken some finesse in setting up the triggering and delays to actually capture the picture.  That understanding will only come with use.

Thanks, RTR and GRJ for latest replies.  All of that helps prepare to learn from using scope.

To that experiment.  After I came back from removing the egg from my face, a remarkable measurement to report.  The 37V Zeners measure 1.0 nF (1000 pF) on my meter, in the ballpark you estimated, GRJ.  But the kicker I left out.  One place I put Susan’s filters is at the TIU outputs, in addition to the end of each block for signal reflection damping.  Guess what the capacitance of the combination is?  The filter adds about 100 nF (100,000 pF), a hundred times what the Zener does.  With both removed from TIU output, same PS2 switcher, same track location, signal 9-10 and engine works.  A “more is not better” example for sure.

Unfortunately, 20 feet down the track in the direction of the end of that block, signal fades to “not found” and control is lost.  I know removing filters at block ends is next thing to try.  I am curious though.  Superwarp1 posted that SD’s filters decrease signal on his layout with Rev L TIUs.  Is there a reason in the Rev L circuitry that would explain that?  How does a TIU that is designed for stronger signal, tolerate the capacitance of those filters less well than a lesser TIU?

I have to ask, just how many filters did you install per TIU channel?

cnwdon posted:

I know removing filters at block ends is next thing to try.