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.  

I've never fully understood how the filters worked with earlier versions and degraded the Rev. L signal.  Yes, the Rev. L has a stronger signal, but that shouldn't go in the tank with the filter.

One thing you forgot to note about the filter.  You measured simple capacitance, and the filter has a 221 ohm series resistor.  The capacitive reactance of the .1uf cap is significant, but the impedance presented to the load at 3mhz is 221 ohms.  For the TVS, the impedance to 3mhz is much lower, around 35 ohms. The TVS will affect the DCS signal considerably more than the filter.

Susan Deats DCS Filters.

OK, interesting, one of those mysteries we won’t likely solve.  My understanding of AC impedance issues and what influences that remains primitive, as is obvious.  DC and resistance is so much simpler.  

Engineer Joe, each channel on the long mains has (had) a total of five filters, one at TIU output and one at each end of two blocks per channel.

I removed all filters from one main (which is one channel) and the PS2 switcher now has a signal of 9-10 almost all the way around the 130 feet of main, in both blocks.  One stubborn stretch of track where it drops to 3-4 (was “engine not found” before removing Zener and filters) but seems not to lose control of engine.  The track has both soldered pin connections and 12 gauge busses with frequent drops to all 3 rails, so there is not much to change there.  If control is maintained, seems not a thing to waste much worry about.  Two PS3 locos each continue to show signal 9-10 everywhere on main.

One new PS3 (boxcab switcher just produced in last year or so) has intermittent loss of diesel engine sound sometimes with garbled tweets in its place.  The other has no such problem.  Should I look for a bad connection to speaker or similar simple issue inside?  (This question relates to no local MTH service center in Portland OR area, nearest has 5-6 month backlog and is 170 miles away, so not of practical help unfortunately.)

have you lubed the rollers and axles? Maybe something simple. Sometimes the sound set is corrupt. I would think a speaker going bad (or wires shorting) might drive the board nuts too?

Some engines lose ground side easier. Try a test of connecting your outer rails together if they aren't.

cnwdon posted:

One new PS3 (boxcab switcher just produced in last year or so) has intermittent loss of diesel engine sound sometimes with garbled tweets in its place.

gunrunnerjohn posted:

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.

Exactly! That nicely sums up my scope experiences so far.

Found this clearly written tutorial for scope use this morning 

https://learn.sparkfun.com/tut...ope/all#introduction

Looks like a good start.  You'll never know what you don't know until you stick the probe on your own circuit and try to figure out what you're seeing.

Some experiments today that are starting to belong on the “Weak DCS signals, Failed TIU channels, etc” thread.

1. Disconnected the other block from the TIU channel in question, testing with just the “problem” block for half of that mainline connected.  For the PS3 engines, this seems to have taken lowest signal spot that was +/- 8 and made it a 10.  It didn’t cure the PS2 engine signal.  Having “engine not found” problems with that today.

2. Removed an unnecessary “Scott’s Odds n Ends” spike suppressor on the output side of TIU, since I just learned here that the Rev L TIU has its own spike suppressors on the output channels.  No measurable change.

3.  Removed the DM “buffer” TMCC signal booster completely (it had already been turned to lowest gain) and left just straight output from Legacy base to track.  This brought PS2 loco’s signal reading from “not found” to 3 or 4, but there was still a lot of inconsistent junk happening with functions: horn blows, but bell might go on but not want to shut off and engine won’t move with speed advanced and XX MPH showing on remote.  Signal strength at the same time (!!!) as high as “10”, so this is hard to explain.  Some sort of signal interference that doesn’t show itself in the overall “signal packets” score for signal strength.  But random unpredictable stuff seems to be the name of the game, a good part of the time in this series of tests.  Even the PS3 locos, before removing TMCC signal, had problems with “engine not found” at times and the spotty malfunctions noted.

4. Finally removed TMCC signal entirely, in addition to absence of Scott’s spike suppressor (and absence of Deats filters, and absence of my Zener TVS’s) and having only one block connected to the channel.  Now for PS2 and PS3 locos tested so far, full function with signal 10 where it once was low.  Haven’t tried adding back the second block yet, but will.  This leads to the frustrating possibility that DCS cannot be operated without disconnecting all TMCC from the part of the layout where the DCS loco is running at the time; as the one club reported on that other thread, that they gave up and no longer try to have Legacy and DCS operating at the same time.  That is not a desirable outcome.  Even if I were to operate only PS3.0 engines, from today’s testing it’s not clear that would cure the problem.

5.  Question: if I do wind up putting each block on its own TIU channel, is there any reason the 2 channels feeding the blocks for one mainline can’t get their AC 18v input from the same transformer output terminals that have been feeding the single channel serving the two blocks, until now?  There isn’t a problem with too many locos etc loading the power, and this is all for one mainline.  That is, “Y” the hot and common power feeds from one side of transformer, so they serve both channels.

We ain’t got to the level of an oscilloscope YET, but quite a series of trials already—Whew!   We have something out here from Deschutes Brewing called Jubelale, every winter.  Time for one of those....

cnwdon posted:

 

5.  Question: if I do wind up putting each block on its own TIU channel, is there any reason the 2 channels feeding the blocks for one mainline can’t get their AC 18v input from the same transformer output terminals that have been feeding the single channel serving the two blocks, until now?  There isn’t a problem with too many locos etc loading the power, and this is all for one mainline.  That is, “Y” the hot and common power feeds from one side of transformer, so they serve both channels.

 

Once you connect the neg- or common with the TMCC/Legacy signal on it, you will have that problem.

I had to totally isolate my tmcc from my DCS. That also meant separate power transformers.

Egr. Joe: thanks, but my question relates only to sharing the power with DCS only on system.  That is, TMCC is “gone”, not part of the situation any more.  Now, I’m proposing to take the output from one side of a Z4000 and branch the hot and common leads so each connects to two TIU channels on the same TIU, one channel for each block of a single mainline.  I should get the advantage of lower capacitance per channel with some 60 feet of track and busses removed on each channel, but don’t need two power inputs, since it’s the same mainline that now has just one TIU channel connected to it.  Any reason that should not work, before I try it?

No problem at all connecting one power source to multiple TIU channels, that won't affect the DCS signals at all.

Follow up on yesterday’s experiments: confirmed again this morning that signal on the divided mainline (one block, about 60-70 feet of mainline and bus wires) remains 10 for PS2 and PS3 locos, including places it was very low or nil for PS2 and significantly lower for PS3 with TMCC connected.  I reconnected the Legacy base to the track, and at the formerly best signal location (when it varied), the PS2 engine dropped to a “4”.  The PS3 boxcab still showed a 10, but also showed some of the odd behavior mentioned above: it started up without a command, and did not move with the speed control advanced and showing a speed on the controller.  Disconnected Legacy base again, and it went back to normal: didn’t start until commanded, moved normally.

There has to be some sort of signal interference or “false” signal introduced to the track with TMCC connected to account for this.  Others must have had similar experiences; hope some will see this thread and chime in.

Adrian has documented the possibility of Legacy and DCS clashing, it's something that's been observed in a number of locations.  One thing you might consider doing if the Legacy is working fine is adding a voltage divider to knock down the amplitude of the legacy signal around 50%, that would reduce the likelihood of it clashing with the DCS signal.

gunrunnerjohn posted:

Adrian has documented the possibility of Legacy and DCS clashing, it's something that's been observed in a number of locations.  One thing you might consider doing if the Legacy is working fine is adding a voltage divider to knock down the amplitude of the legacy signal around 50%, that would reduce the likelihood of it clashing with the DCS signal.

Thanks. Google and Sparkfun.com have educated me about the basics of a voltage divider.  Taking your simple 50% suggestion, 3 questions:

Proposed values for the two (equal) resistors? (Does it matter?)

Since TMCC has a single output and no return path to the base, should I ground the voltage divider to the house ground? (specific thought, would be the same electrically as my ground plane wires, which connect to the ground at the outlet supplying power to the Legacy/TMCC base.)

If I don’t get peachy results with 50%, potentiometer for one or both resistances to allow tuning?  (Seems one enough, if the fixed value is chosen well)

The voltage divider would be returned to the earth ground on the command base, that would be either pin-5 of the serial port or the outside barrel of the power jack.  You can also use the ground lug of the power plug on the same outlet as the command base.

I'd start with a couple of 150 ohm resistors in series, command base track signal on the top, earth ground on the bottom, and track signal feeding out the center.  The values of the resistors do matter as the TMCC signal has to drive the capacitance of the track, so too high a value will minimize the amount of drive.  Too low a value will slam the TMCC signal right at the command base.  I think 300 ohms of load is a good first step.  First step, see if TMCC works well with the divider in place before you bother to add DCS.  Obviously, if you break TMCC/Legacy, no sense in tinkering with that solution.

Cool,  thanks

GRJ, in searching for something else, came across your 6/11/2018 post on the “Tutorial on DCS wiring” thread re: your TMCC buffer (I hope it’s similar to the “DM TMCC buffer” [that’s its trade name] recently produced in a short run by another forum member following a concept Dale Manquen developed, that I have, presently not in service as above noted).  Can the buffer be used for increased signal “drive”, while also using a voltage divider to limit TMCC signal voltage/amplitude, or is that mutually conflicting?  Don’t want to forget the question, as the testing continues 

You could actually install a higher value pot in the variable amplitude adjustment and have the buffer provide lower voltage than the input while still having the low impedance drive, I've never had the need to do that, but it's an interesting idea.

The primary issue the TMCC buffer is addressing is the stray capacitance between the outside track and earth ground.  That capacitance is what loads the TMCC signal and reduces it's amplitude.  With the buffer, we did two things initially, increased the amplitude of the TMCC signal and also lowered it's drive impedance so it could drive larger capacitive loads.  Even without the increased amplitude, the buffer still offers the low impedance drive.  Yes, the DM TMCC Buffer is the "TMCC Buffer". 

The DM was to recognize the huge input that Dale Manquen had on the buffer development, he designed the original and traveled around the country testing it.  His untimely death cut short our production for a spell, but then I picked it up to finish what Dale had started.

GRJ: Sorry for the string of questions, just found this post from Adrian in Weak DCS signals thread, and asking can you offer the suggested work on my TIUs?  (And I guess, how long is your work backlog ?)

”The mod I've done in our club and the SD3R club (TVS + silicon clamps) seems to be invincible, we haven't seen any damage in 7 months. The signals remain 14V pkpk week after week since Nov 2017. The MTH mod in the service bulletin is half of the mod we did (the TVS without the silicon clamps). In that condition we did see failures, not not as frequent as the bare Rev L TIU. The TVS devices are easy to put in, but the clamps are complicated and require a lot of rework and parts meaning it's not too practical for MTH to offer it. My setup is very prototype-ish and needs serious work to install but guys like GRJ are working out cleaner and easier to apply versions. Perhaps the answer will be to send your TIUs to someone like him if you want the highest level of robustness.”

“You could actually install a higher value pot in the variable amplitude adjustment and have the buffer provide lower voltage than the input while still having the low impedance drive, I've never had the need to do that, but it's an interesting idea.”

Recognizing it’s more clunky, would a voltage divider downstream of the buffer signal output, with variable pot in the divider, provide the same result?  Alternatively how to change the pot in the buffer, and a part number for a suggested pot, would be fine too if it’s easy to disassemble w/o damaging the unit. Thanks.

This is a drop-in replacement for the 2K pot in the buffer, it increases the attenuation range so that you could have a 50% amplitude output.  It would be pretty easy to change out the pot, there are two wires going to it.  You'll also find a 1K resistor there, you retain the resistor and just drop in this one for the 2K pot.

Bourns PDB181-K420K-502B

I'm not willing to take on putting Adrian's TIU fix in, it's a lot of work and it's hard to see how I could charge enough to justify the work.  I have a simpler solution, but we haven't proven 100% that it's going to last a long time.  Hard to imagine a problem, but I'd like more time in the field before I declare success.