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Hello Everyone. This is something I posted over on the Aristo Forum where I spend most of my time. But a few peopel suggested I post my questions here too. I also spoke with Axel from Train-Li about it.

Last night I was running some more trains and looking for any issues. I had two dash 9s pulling a coal drag about 30 cars long with a lighted caboose at the end. While that was making its laps around the back yard I added 4 more sd45s to the rails as a second consist. The weird part was every time the sd45s started to move or speed up, the coal train slowed down. Now this reminds me of my old HO days if too many trains were on the rails they would run slower. But in this case they were all DCC locos and I have a 13 amp power supply powering the layout. The booster is only capable of putting out 10 amps so I would assume if I had used that many amps I would have blown a fuse or melted the booster or something. I doubt if I actually hit 10 amps. You guys have any thoughts on this?

To make things stranger the sd45 consist jumped a switch and shorted out. But the coal train kept going. When I went over to the sd45s the lead one had lots and lots of smoke coming out of it and i could smell burnt plastic. I don't know if shorted out because it jumped the switch or if it was just coincidence or what. I think it was just the loco that shorted out because the rest of layout kept operating. Anyhow The smoking unit seemed to move again as i tried to pull it off the switch, but then i stopped it. I haven't I decided to let it cool down for the rest of the night and haven't tested it yet.

Not sure if this is a DCC issue, a lack of power issue, or something else? It is very strange to me.

-Pete
 

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Discussion Starter #2
My PSU is 351W 27 VDC 13 A regulated (i think) with a voltage adjustment range of 26~32 VDC. The voltage tolerance is +/- 1%, line regulation +/- 0.5%, load regulation +/-0.5%. I am not sure what the last two refer to exactly but the voltage tolerance should mean it only differs by 1% or less than a volt in this case. It also lists "100% full load burn-in test" as one of its features. Not completely sure what they mean by that.

Now when I first got my DCC system I powered it with my Aristo Elite which worked but the locos only ran at about 75% throttle. This was due to a voltage drop of about 5V through the command station/booster and decoder. The Elite puts out 22 VDC at 13A and is a very very nice supply. But with a 5V drop that means only 17 volts at best. I got the above supply so I can get 22 V to the rails which makes a big difference in performance.

Anyhow, the reason I thought it was strange was because not only did the locos slow down, but with both conissits at full throttle, they were both running at less than 50% of their top speed. I have run big lashups before with my trackside TE and I don't think I have ever seen the load on my Elite go past 6 amps or so. That is why I was somewhat supprised.

A few suggestions have been made on things I can test. The voltage across the terminals of the PSU under full load, and coming out of the booster as well as on the tracks as the trains are running. Also the amps by putting my multimeter inline between the psu and the command station.

For once power distribution around the layout didn't seem to be the cause of the issues. But as far as wiring goes my tracks are fed by 12 gauge multi thread outdoor wiring. but the wires going from the PSU to the DCC system, and the DCC system to the track feed(s) is only a about a 16 gauge wire. Could this be causing the issues?

Also the terminals on the DCC system seem to be set up to only accept a 16-14 gauge wire. Could this cause this sort of issue?
 

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The first thing I would check is the amps that each engine draws. If you are close to the maximum amperage, you may have problems. How often have you been somewhere when the Air conditioning unit kicks in as the lights dim. With what you were running I think that you were close to maxing out.

Chuck
 

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Very possible you have voltage drop issues on the layout, and you can have a short and still have voltage elsewhere, in fact that reinforces the theory that you have voltage drop (conductivity) issues.

The way I track these down is put a big load on the rails (I have a box that clips to the rails and draws 8 amps) and measure the voltage drop right there.

You can use thicker wire right after coming out of the dcc booster, remember the resistance (loss) from wire is a function of the wire diameter AND the length... so short sections of 14-16 gauge won't hurt.

Greg
 

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A well regulated supply does not lower its output with a line voltage reduction, this is why they are called regulated supplies!!!

All the regulated supplies I have seen will tolerate a 10 percent change in line voltage and the output will be constant.

Also, my elite has an adjustment inside and I set it to 24 volts instead of the Aristo 22.5 setting.

All the LGB supplies I have seen are unregulated as is the Aristo Ultima.
 

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What kind of central station are you using? What kind of rail joiners? My suspicion is that when the load increases you are losing voltage through some bad connections or to ground etc. As Greg suggests, put a load on the rails and go around to each joint and find out if there is one or more bad connections. Also, I'm wondering why your central station didn't trip immediately with the locomotive shorted. Maybe you can adjust the setting to make it shut down more quickly.

Keith
 

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I guess the first thing I would check is the current output from your DCC when you have all of your locos running. See how much current is being demanded from the DCC first. Also you might want to check to current into the DCC system and the voltage level when things slow down. Certainly, as has been said, if you have poor connections on your track you could have a short and it would not shut down the DCC system. Then I would want to know if it matters where on the railroad the slow locos are?
Bob
 

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Discussion Starter #8
Thank you for the info thus far....
To add some more info.... My command station and booster are NCE. I use the 10 amp radio equipped system. As far as the trains on the night in question they were running uniformly around the entire layout. That is to say all the connections were good and the trains did not slow or stall due to track issues. I was able to run one train at a time with no issue. They only slowed when I tried to run both consists at once. The effect was also uniform around the layout as well.

-Pete P.S.

Is there a way to increase font size on this forum?
 

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Hi Pete,

I think it must be the NCE station that is the limiting factor on output. 2 Dash 9's plus 4 SD45's is 8+8= 16 motors isn't it? So under heavy load each of those motors must be an Amp each which puts you way over the 10A. I don't know much about the NCE gear, but I think I'd be looking at why it didn't trip out when the SD45 shorted. Can't you adjust the time to shut down when a short is detected?

Keith
 

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When you put additional motors in a loco, it does not draw much more than one single motor under load. The same goes for multiple locos. There is of course some loss of extra lights and frictional losses, but basically if you need 3 amps to pull a train with one SD45, then two SD45's pulling the same train will be about 3 amps too.

The NCE system itself (remember it does not ship with a power supply), given enough power, can put out 20 amps for brief periods.

This is not about the NCE output, it's basically on or off... It's most likely power loss somewhere, or a defective power supply (which I doubt).

Trains running well does not mean you don't have issues... double the load will show up problems you did not realize you have.

I think we've given a number of suggestions, let's hear the results of testing.

The first should be current and volts at the output of the power supply (where it is going into the NCE booster)...

Next I would suggest my load test at the far end (electrically) of the layout. If you can deliver your full 10 amps out there, that's half the battle.

Greg
 

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Pete,

One thing you mentioned was that it was at night....was it damp or cooling/condensing that night? That will make any grounding/voltage leaking problem much worse I believe. I would try it in the middle of a warm dry day and see if it's any different.

Keith
 

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Posted By Cougar Rock Rail on 13 May 2011 11:12 AM
Pete,

One thing you mentioned was that it was at night....was it damp or cooling/condensing that night? That will make any grounding/voltage leaking problem much worse I believe. I would try it in the middle of a warm dry day and see if it's any different.

Keith

I've witnessed this same phenonom for my track power and even noted it on the Aristo site, (but it was ignored).

At night the dew point drops and the resistance between the rails goes way down as current bleeds off through the moist soil and ballast. Couple this with the moisure that collects on the rails that serves as an insulator to the wheels and we have the receipe for very poor performance. This moisture on the rails also seems to promote arcing and carbon build-up on the wheels.

I clean my rail at the beginning of a session during the day (around noon) and trains run great until the sun goes down. After that, if I'm running trains, I'm out there continually cleaning the track (and wheels) to keep the trains running smoothly.

As I said on the Aristo forum, put an ohmmeter across the rails and take readings throughout the evening/night to see if this is occuring for you.
 

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Moisture on the rails is very interesting as I run a pair of SD-45's with lights, smoke and sierra sound in both with everything on and in the rain.

They run just as well as on a dry day.

So I guess you must run on wet rails in New England to not have issues. :) ;-)
 

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I know there are leakage issues when the rails are wet AND it's not perfectly pure water, but I have run in the rain and with completely wet rails and never had a problem, there was plenty of voltage to go around.

When I ballast / surface (prototype talk for re-leveling) track, I often do it with a train circulating (so I can see the improvement) and will hose the track down after dumping the ballast to wash the dust from the rails... never a problem...

Greg
 

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Then maybe you have a better explanation as to why the worst offending spot is behind the waterfall where the soil is the wettest and the second worst is next to the hot tubs that wet the tracks? These spots are even problematic during the day.

Ask people who have trains that run behind/next to waterfalls, where the track takes the splash, where they have the most problems with trains stalling. I'm betting its similar. And yes we have hard water.
 

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Posted By Peter Brayshaw on 12 May 2011 11:17 PM
Is there a way to increase font size on this forum?


Just use the feature of whatever OS you're using.
On the Mac which I'm using right now, I just hold down the command key and hit the + sign to increase the font in steps (or the - sign to make it smaller.

On your train related issue - you need to take the measurements already suggested and post them here.
Right now everyone is groping in the dark and is just coming up with guesses.

It's pretty obvious that there is a drop in DCC voltage that makes the trains run slower but it's not clear what is causing that.
If you don't know how to measure DCC voltage or DCC current then ask - you can't just use a regular multimeter for that.
The multimeter as is is good to measure the DC voltage of your power supply but I doubt that's the issue.

Knut
 

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Let me toss in another possibility, based on a similar problem I've had since last Fall.


My command station and booster are NCE. I use the 10 amp radio equipped system.


The light went off because I have the same system.


I noticed one day that whenever I turned up the power above 18 (out of 24), both my Aristo RDC and USAT S4 would slow down. Bringing either one up to the full 24 would stop everything. Yet they both ran very nicely as long as I kept the power at 17 or below. I started searching for connectivity issues in the track.
With the rains this Spring I haven't had much train time but saw that the problem hadn't cured itself over winter. Still figuring it was a track problem I built this gizmo:



It my patented "V-O-M on a Stick"! At the bottom are two metal cup-shaped things I found in one of my many junk boxes:


Now I can read track voltage without crawling around on the ground.

After a couple tours of the entire layout with nothing running, I found that the NCE was giving me a consistent 16 volts everywhere. Then I checked voltage in front of and behind the moving engines - not so easy to do with a standard pair of probes. I determined that the RDC is okay, but when I put the S4 over 17, the voltage drops. The S4 started its life working fine, but apparently now has an internal (decoder) problem.

Maybe I'm not the only one with that problem???

JackM

I am hesitant to mention this because it's common wisdom that the NCE's smaller decoder (D408) is okay in USAT engines in spite of NCE's warnings. That's what I've had in the S4 since day one. I'm in the process of installing the more robust D808 now. It's possible, of course, that the decoder died not from normal use but from an "extreme event". Or perhaps my particular unit was destined to fail under any circumstances - it only had a few months of use. I'm not drawing any conclusions from my personal experience.
 

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While we wait on Pete's results, I'd say that you might want to check some other stuff in your S4, did you remove/disconnect the other electronics that were in there, like the voltage regulators.

I've seen decoders (Tsunami) that will shut down on "over voltage", but nothing that does what you say... it's like a short over a certain track voltage...

Greg
 
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