[ChrisA117]

Thanks for stopping by to help a newbie here (if possible). I have a pair of MTH Dash-8 locos controlled via DCS android app on LGB brass track via the following components (with 10/10 signal at all times):

Z-1000 PSU: 40-1000A | MTH ELECTRIC TRAINS (18VAC @ <5.5 A)
TIU + Wifi DCS: 50-1036 | MTH ELECTRIC TRAINS
2x PS3 Locos: 70-2123-1 | MTH ELECTRIC TRAINS & 70-2124-1 | MTH ELECTRIC TRAINS

The issue I'm having is that each locomotive runs at different sMPH. I specifically purchased this pair to run in a consist, but if each locomotive is working against each other to maintain its own speed, inevitably this will cause permanent damage of some kind due to the digital speed regulation increasing torque as necessary to maintain a particular speed.

I have tested this problem at all variety of speeds and the issue persists. The difference does scale linearly with speed (aka low speed = small difference, high speed = larger difference). When I first received the locos, I sent them both in for warranty service as I didn't know which one may be at fault. The service center found some other issues, fixed them, and ultimately said there's no way to make them match speeds and that both are functioning correctly.

Has anyone else had this issue?
Do you know of a fix of any kind (without deviating from DCS)?
Am I actually SOL here with DCS? I'm open to tinkering/manual modifications to fix this issue if necessary to trick one loco into running faster or slower, either electrically or mechanically (maybe timing wheel modification?), but I figured I should consult people with far more experience than me first!

Thanks for your time!

- Chris

 

[Greg Elmassian]

That is just plain crazy!

Are both stock, or was one upgraded? Analogous question, are both PSII or PSII or ???

The tach strips on each one should have the same number of stripes. Supposedly with identical gearboxes (and I am unaware of any differences) and the tachometer strip, they MUST run the same speed... very weird.

Greg

 

[ChrisA117]

That is just plain crazy!

Are both stock, or was one upgraded? Analogous question, are both PSII or PSII or ???

The tach strips on each one should have the same number of stripes. Supposedly with identical gearboxes (and I am unaware of any differences) and the tachometer strip, they MUST run the same speed... very weird.

Greg

Greg, I agree this is absurd! They were both bought within a couple months of each other directly from MTH awhile back. I'm just now getting around to seeking additional help. They are both PS III locos and I have examined the gearboxes closely on each for any deviations or defects and found none.

Chris

Edit: They are also both stock... NO modifications have been made at all. Both are properly greased/oiled as well.

 

[Greg Elmassian]

As I understand it, there is no DCS command that could affect this.

One thing I would try, is if you have a friend with DCC, perhaps changing one of the CVs related to start speed, or speed table could have had an effect. It does not make sense, since the absolute speed control by tachometer is at the foundation of the drive system, but the DCC "addition" is poorly implemented, it could have issues.

I'll try to find my PSIII DCC CV table and see if there could be anything. This could easily be overlooked by the service department.

Greg

 

[ChrisA117]

As I understand it, there is no DCS command that could affect this.

One thing I would try, is if you have a friend with DCC, perhaps changing one of the CVs related to start speed, or speed table could have had an effect. It does not make sense, since the absolute speed control by tachometer is at the foundation of the drive system, but the DCC "addition" is poorly implemented, it could have issues.

I'll try to find my PSIII DCC CV table and see if there could be anything. This could easily be overlooked by the service department.

Greg

I agree that is the case. It would be nice and relatively easy I imagine for their software engineers to add a software level speed offset, similar to the DCC speed tables... but I'll keep dreaming on that one.

I did toy around with DCC control via DCC++ or openrail or something along those lines as it didn't cost me much to experiment with that as a fix. I used an Arduino as the brains/interface with the track in addition to a power supply (forget which type) to implement this. I was able to control both trains over DCC but experienced the same result. I can't remember if I manually adjusted any speed tables to try to compensate. I DID reset all DCC programming variables multiple times though. I also performed a DCS factory reset on both locos multiple times with no change to the problem.

Thanks for looking into this for me Greg.

Chris

 

[Greg Elmassian]

Looks like there are enough CV's that you could get messed up...

Look at the CV for start, and also there is a vmid and vmax CV (per the nmra standard)

also zero out the momentum CV's

that would be what I would do first.

https://ncedcc.zendesk.com/hc/en-us/articles/201499765-MTH-Protosound-2-CV8-27

ahh... a better list for PSIII with a chart:

https://ncedcc.zendesk.com/hc/en-us/articles/203794919-MTH-Protosound-3-CV8-27-

Greg