Z-4000 On The Fritz

@ChiTown Steve  Boy lots of questions -

The handle adjustment screws only serve to put more force between two gears inside the transformer. If the handle gets too loose, the potentiometer which controls voltage can get out of alignment and then never get back to "zero". When this happens you get a transformer fault and nothing gets out to the tracks. Time to pull the cover off and re-set the gear alignment. There are forum posts on how to do this.  However this does not seem to be your issue. I just "fixed" mine for the second time.

You do not say whether your engine speed variation is happening when you are running DCS or conventional transformer. I would get a voltmeter out and check voltage readings along the track. Sounds to me like there is a power feed issue (something is loose) or there may be some "dirt" on the tracks in places.  That said most suggest having a light installed across the rails - it tends to provide some sort of buffer that smooths out voltages and control signals. My Z will show 0 volts on one side and 0.1 or more on the other - never zero, but I also have never installed the recommended light.

You are very brave and precise if you place 4 passenger cars on the track while powered. I would produce all kinds of arcs and sparks and blow the breaker.  I am not sure going from no load to a load and watching the voltage on the Z is representative of what is going on. If you are pushing out 18 volts, when you add load the voltage reading should remain constant, but there would be current draw.  More representative would be to have the cars on powered up and then remove one or two. There should be no change in voltage.

My bet is there are loose or corroded connections somewhere. Recently someone posted about replacing the banana connections on the back of their Z due to overheating. Other than resetting the potentiometer I do not think there are user serviceable parts inside - unless you know how to work with circuit boards.   

BTW I am assuming your feed wires are of adequate size to provide near zero voltage drop due to distance resistance.

Thanks ScoutDad,

I use DCS powered by the Z4000. I use 14 gauge wire in home run fashion. I’ve always had 10’s all around on the signal strength. I measured the voltage on the track at various places and it was the same.

The track is cleaned once a month, overkill but I still do it.

I just swapped out the Z and used my 80 watt Williams. I ran it for 20 minutes and everything was fine. No speed changing at all.

I’ll do the resetting of the gear alignment next. It could be it. The banana plugs are clean but maybe who knows  

I really don’t like any of the other transformer options out there. Either underpowered, too much money or not available.

Thanks Again.

@ChiTown Steve  Your reply just popped up in my email. 5 days.  If you are not getting the fault light on the Z, there is no point in "resetting" the gears. What are you using to get from your terminal block where you track wiring comes together to the Z's banana jacks?  I find the plug connectors from MTH to be sloppy and made my own connectors using stereo plugs - nice tight fit. But if you were using the same connectors with the Williams transformer - maybe that would rule out wiring. But intermittent bad connections are really hard to track down.  When the engine surges are you seeing voltage swings on the Z? 

I also like the power supplied by the Z. There are circuit boards inside the Z, if something is starting to fail maybe that is causing the voltage changes.

Thanks for responding, I was just about to post what I've found. This is really long but it kind of needs to be.

Layout Configuration

The GarGraves track is 20 years old. The wiring is 2 years old as we just downsized to a new house (Naperville). 14 gauge twisted pair home run to 4 quadrants so that I can use crossing gates etc. Everything to the track is soldered. DCS and iphone app. I don't use banana plugs at the Z, instead I run the wire through the hole in the post and tighten the red/black knobs.

The layout controlled by the Z is track 1 mainline (left handle) and track 2 mainline (right handle). Each mainline has passing siding by using left-right 072 turnouts. All sidings can be turned on/off by a switch to the center rail.

Layout Test

I took the Z off the table and replaced it with 2 Atlas O 80 watt transformers. Siding 1 of both mainlines is a passenger train, siding 2 is freight. Every engine is Proto 2. I used different sidings, and ran each train for 20 minutes. Running this way was flawless.

Bench Test the Z

On my workbench I had 2 Gargraves straights wired for each handle. I put left handle to 17 volts, I added the 2 passenger cars. It dropped to 14 volts. I kicked the voltage back to 17 volts. I took off the cars, it went to 20 volts. I did the same test with the right handle, same result. I put both handles at 17 volts, added cars to left handle, left handles drops to 14, right stays at 17. Kicked left back to 17. Put 2 cars on the right handle, it drops to 14 while left stays at 17. For all of this I confirmed that the voltage at the track matched the voltage displayed.

Wire Z back to the Layout

Left handle I ran the passenger train at 17 volts. No problem. I stopped the passenger via DCS on siding 1, switched the turnouts to curved and ran the freight train. No problem. Then I toggled off siding 1 with the passenger train, while the freight train was still running, boom went to 20 volts.

When I run trains I'm switching the sidings on/off all the time. Part of how I enjoy the layout is having different trains going different directions, replacing the trains I have on the layout etc.

Conclusion

1) Being an IT guy for 40 years this feels like a software bug. On my old layout I just had 2 loops without sidings so it's possible it's always been this way and I never had a reason to notice.

2) In running trains on the new layout for the last 2 years I only recently noticed this. So maybe there is a connection inside the transformer coming loose? I haven't had time yet to open it up.

Thanks for hanging in there with this. I'm thinking of keeping the Z now knowing this quirk is there. If it gets worse I'll replace it. The wife is fine with me spending near 1K on a new transformer. I'm not TBH.

I'm open to all thoughts on this.

@ChiTown Steve  If I understand what you are doing, having a DCS engine on a siding that is powered off and then powering the siding back on will cause the engine to start-up in conventional mode. And zoom ... Gunrunnerjohn builds watchdogs which will allow this kind of operation. If you have the DCS Companion look up the Watchdog Signal.

As to turning off track sections (blocks) I can do the same on many parts of my layout, but as I am finding out, it is not as simple as flipping power to the track section. For now, I put all the engines I intend to run on the layout and then turn on power to the WiFi and TIU. Once I have a signal to my app, I'll then raise the power to 18 volts. Then I can start-up select engines. If I do have one on an unpowered siding, its then drop voltage to zero, power the siding and then bring power back up.

I'll have to try putting passenger cars on and off the track. I do not recall seeing the voltage behavior, but I have not looked or noticed. 

@ChiTown Steve  check out this explanation on voltage versus impedance.

https://en.wikipedia.org/wiki/Electrical_load

Mathematically it shows how you can get a voltage drop if the internal resistance of the transformer is close to the resistance of the load. Been a really long time since I took the circuits course in college. Forgot about this "exception".  Their example is seeing lighting dim when a heavy power draw comes on.

@ChiTown Steve posted:

Left handle I ran the passenger train at 17 volts. No problem. I stopped the passenger via DCS on siding 1, switched the turnouts to curved and ran the freight train. No problem. Then I toggled off siding 1 with the passenger train, while the freight train was still running, boom went to 20 volts.

So basically you had the voltage set to 17 volts with a passenger train (which has lights) and you started to run a freight train (no lights) and turned off the siding with the passenger cars (turning off the lights in the passenger cars in the process) and the voltage went from 17 to 20? Yeah that's normal. Less draw results in higher voltage at the rail, as the transformer isn't working as hard. Z4000 will put out around 22 volts with the throttle all the way open.

If I have nothing on the track on one of my layout mainlines the PH180 that powers it puts 18.5 volts to the rails. Stick a twin motor diesel pulling 6 illuminated passenger cars on the track and voltage at the rails drops to 16.5 volts. Shut off the train and the voltage pops back to 18.5 volts at the rail. 

Thanks Lou, Apparently I’m just overthinking this. When I see 20 or 21 volts to the track I start worrying about engine electronics. I’ll remember in the future to drop the voltage before toggling off any passenger trains.

@ScoutingDad posted:

@ChiTown Steve  check out this explanation on voltage versus impedance.

https://en.wikipedia.org/wiki/Electrical_load

Mathematically it shows how you can get a voltage drop if the internal resistance of the transformer is close to the resistance of the load. Been a really long time since I took the circuits course in college. Forgot about this "exception".  Their example is seeing lighting dim when a heavy power draw comes on.

Thanks I’ll check this out this weekend when I have time to focus on it. Counting down the days to retirement.