Runaway Train - Not responding to DCS Remote

Easy, notice your two symptoms- one which you failed to mention.

You lost chuffing

You have runaway speed control as soon as a speed is commanded

= you lost tachometer feedback control. The wiring, the senor, or the flywheel tape is not providing a pulse or RPM speed back to the system.

All locosound, PS2, and PS3 engines have and require tachometer feedback to both control the speed and provide the timing signal for chuffing sounds on steam engines.

It's could be a failed tether wiring problem, a failed optical tach sensor, tape or stripes missing on the flywheel, or just simple misalignment or spacing of the sensor compared to the stripes.

I recently had to repair an engine and it was the tether for this exact problem. The user was running the engine on a tight 031 track and eventually enough hard flexing of the cable and it failed.

Again, bench testing this engine on rollers or on its side on the bench, even in conventional, the tachometer is used for chuffing and clearly in your video you had none- combine with ramping up speed runaway.

Also, you need to post the product number of this engine. I think yours is the Railking version given your tighter radius Fastrack layout.

So this engine? https://mthtrains.com/30-1116-1

What does your box say?

Cab No. 1604 Die-cast Articulated. First Time 2-6-6-6 Engine for 3 Rail O-31 with Proto-Sound. Box cataloged with incorrect item number 20-1117LP. Correct Item number at the time was 30-1117LP which was later converted to 30-1116-1 in the accounting system.

Also, it's possible seeing yours has the wire tether, maybe this was an upgraded unit with either PS2 or even possibly PS3?

Bottom line, the failure diagnosis doesn't change much, it's again for sure the board is not seeing the tachometer, the how and why behind what is wrong could be a few things. Also, given this most likely is the Railking and the motors pivot inside the engine, then that tach wiring has to flex with the motor. Thus, if it worked before fine, and then one day stopped, my 2 big first ticket items are the tether between the engine and tender, and possibly that wiring inside the engine leading up to the tachometer sensor on the motor.

Vernon, Thank you very much for your detailed response. I am very much a newbie on this stuff and my son was the one who plays with the trains. So are you basically saying, there is something wrong with the train physically and I will need to open it up and look for any crimp wired or broken connection? Or is there something else I need to setup on the DCS Remote? Unsure what you mean by "Lost Chuffing" and "lost tachometer feedback control"

If the issue is hardware related can i find how to fix this online somewhere or I need to send it to someone?

Thank you again for your help!!

Thanks for the quick reply again. I just saw the new post after my post. That is the correct train. We upgraded from PS2 to PS3

Who did the upgrade?  PS-2 to PS-3 is normally a repair but PS-3 steam upgrade is like a PS-2.  I would call your installer.  G

Very interesting thread, I had a runaway MTH engine once, maybe 3 years ago, forget which engine it was. Such a repair was beyond my knowledge and ability. Got an authorized MTH technician, probably GGG, to do it.

I think my repair involved the tachometer.

Arnold

I will reach out to my installer and see if he can look at it, if he can't I will reach out to someone here to have a look at it. Thank you all for the help