MTH: Triplex - Modifications page:

(Click here for MTH: Triplex - Photo & Video Page)



Model Info:


Model Overview:

This is MTH's best One Gauge offering to-date. 




MTH Triplex Repair/Modifications:

Modifications/Topics list:





Replace front coupler with functioning #830 G scale Kadee coupler:


Original 830 Kadee on the right, cut and modified on the left.  Required some filing on the bottom surface of the coupler arm to get it to fit properly.  Also had to drill a hole for the original screw through the coupler arm which holds the coupler in place. (hole not pictured)



The height on the front pilot will be slightly too high compared to the standard Kadee coupler height gauge.  If you plan to couple something else up to it you may need to use a coupler with a greater height offset as I did on the tender of my lead Triplex.  The tender has a Kadee 831 for this reason.








Sharing power pickup between the tender and engine

The Triplex does not have a wire pair that allows sharing of track power pickup between the tender and the engine.  The tender slave board (which powers the tender motor, lights, etc) is dependent on getting power from the tender power pickups to function.  Just ensure better reliability, you can add an additional two wire connector between the two to share track power pickup.   (Note: this is not to correct a problem just an enhancement I chose to add) 


In the photos below, a pair of fuse holders with 3 amp fuses were added to provide short protection between engine and tender. (This is not really required, just an extra precaution).   One fuse holder for each power pickup side.  



Next, a another two wire connector end was soldered to the DCS polarity switch located inside the engine (on the rear frame on the Fireman's side).  The ends of this new connector pair were then soldered to the ends of the connector that would be used to make the connection between the engine and tender.  (Note the new red and black wire connector is to allow for separation of the boiler and frame if necessary.)  The connector wires were run between the space between the existing tender tether connector on the engine and the frame.  That's it.



Note:  I chose actual blade fuses over auto-resetting polyfuses to ensure no more than 3amps max current was allowed to pass between the engine power pickups and the tender pickups.  This was just to make very sure no damage would ever occur as a result of a short between the tender and engine power pickups.  (3 amps was selected based on passed experience with the MTH Big Boy.  Most likely a 5 amp fuse would be safe to use).  Removing the tender shell is quick and easy if a short ever does blow the fuses... and with the way this modification is done, if a fuse ever blows the engine goes back to prior it's prior state where it didn't have shared power between the engine and tender for that power path.  So this is a Zero impact modification.








Improving the sound volume and base levels via modifications in the tender 

The sound and base levels in the Triplex can be improved by doing a few things.  Some are simple, some are a little more involved.   The end result is worth the effort in each case.




1) Remove the rear plastic speaker enclosure cap:


This is simple and relatively easy.  It will require that you desolder the speaker wires from the speaker to get the enclosure off.   Shown is the stock MTH speaker.



Next, nylon washers were purchased and used in conjunction with some similar sized metal ones to ensure the speaker frame was insulated from the metal frame of the chassis.  This is technically not necessary, but it is just in the very unlikely event the speaker blows and electrical contact is made internally in the speaker between the frame and the speaker wire inputs.  This would protect the audio driver circuit from a static discharge passed to the frame or also the unlikely event that the frame gets energized with track power because it comes in contact with a rail in a derailment. (Note in my case in these photos I went the extra step and replaced the speaker with the ones I use in my DCS conversions to get better and fuller base and sound.) 


I confirmed the speaker frame is isolated from the tender chassis with a continuity check via my voltmeter.




1b) Seal the openings in the tender if you remove the existing rear speaker enclosure:


Once you remove the rear plastic speaker enclosure, you will want to seal the air gaps in certain spots on the tender to ensure you get the best possible sound.  There are air gaps in the sides of the frame, around the motor and at the back of the tender.



To block the side openings, I used black electrical tape on the inside and filled it in with square cotton pads to ensure they remained sealed.  Around the motor I also used square cotton pads and placed them around the base of the motor and carefully secured them in place.  Be sure to still allow for the slight movement/play in the motor and the frame.  At the back of the tender I used more cotton squares along the back edge of the tender shell and filled in the space gap between the rear lower part of the shell and the frame.




3)  Replace the speaker: (with better 4 ohm speaker):  (Send an email if you would like to purchase a replacement speaker)


MTH uses good quality speakers in their engines, but for some time I've been using an aftermarket speaker to get better base and fuller sound.  Here is the aftermarket speaker with a factory LGB version.






MTH Triplex - Erie:

                                              Select the version / quality you want to download:


         -  Video #1 - 12:38 mins  -  Speaker comparison tests

                    - 290MB/3000kbs - 99MB/1000kbs - 36MB/400kbs

          -  Video #2 - 1:20 mins  -  Quick compare compilation - focused on chuff

                        (1=Original setup, 2=Speaker enclosure removed, 3=Upgraded speaker, 4= Upgraded speaker open frame, 5= Upgraded speaker+new sound file, 6=Big Boy)

                    - 35MB/3000kbs - 12MB/1000kbs - 5MB/400kbs








Improve the chuff and whistle volume by loading the updated MTH Protosound 2 sound file


MTH has released an updated sound file with improved chuff and whistle volumes.  This new file has been tested and brings the sound levels up to what you would expect from their Challenger and Big Boys.








Adding nylon washers to reduce side to side play of the frame on the axles


This was something I did for the MTH Big Boys to reduce the side to side play to help ensure the sliders did not swing out too far when crossing my Aristocraft 19.5 degree crossovers and cause a short. (see this link for more info: Loss of track power pickup from front engine set - (Shorting on Aristocraft 19.5 Degree cross-over & switch fix)also Slider & Slider screw modifications + Shimming the axles)   


On the Big Boy it was more needed, but on this engine it was done for good measure just in case. 


Because the drivers are spoked, they needed to be trimmed down so they didn't show.  A pie shaped wedge was cut out so they could snap on the axle.  Washers were added to the first and fourth axles on each of the three sets of drivers.


Here they are installed on the Big Boy. 









Adding fuses between the front and rear engine sets


This was something I did for the MTH Big Boy to protect the power traces on the rear engine set power transfer board.  On the Triplex I doubt this is necessary, but I went ahead and added them anyway for good measure. 








Smoking Whistle - No smoke output (No air velocity from fan)


Have seen one case when filling the smoke whistle unit with smoke fluid the stack would get a bubble and required you blow down the whistle stack to clear it.


Another issue I've seen is the fan blade assembly being too high on the motor shaft causing it to make contact with the circuit board above.  This was preventing the blade from spinning. All that was required was to remove the smoke unit from the boiler and press down on the blade assembly with a small screw driver (through the air inlet hole on top) to push it down further on the shaft.  (no disassembly of the smoke unit is required.)


Note visible in the photo are circular marks on the circuit board from the fan.

Blade now properly recessed into the assembly.








Smoke unit smoke coming from inside the boiler


If you see this when running the smoke units, turn them off an take look down the main stack.  (You may need a flashlight.)  Make sure the smoke unit is properly centered with the stack hole.  (i.e. look for the brass ring on the smoke unit and sure it is centered with the engine stack.  Had one engine with the smoke unit off center and it was blowing some smoke inside the boiler when running. 


In my case the solution was to straighten the smoke unit mounting bracket as noted below. 


Main smoke unit mounting bracket, was causing top of smoke unit stack to be off-center. - bent

Main smoke unit mounting bracket, was causing top of smoke unit stack to be off-center. - straight




Once this was straightened the smoke unit could be properly centered.







No smoke coming from the tender smoke stack


If you don't have smoke coming from the tender smoke stack and maybe see some smoke seeping from the back rear of the tender, give a quick blow down the stack, you probably have a bubble that is blocking the air flow.








Marker lights on tender won't come on


I have found that the marker lights on the tender will go out if you turn off the cab interior lights with the remote.  If tender marker lights are off and you want them on ensure you have the front marker lights turned on, then turn the interior light on. 


If you are running the Triplex as either the second or third engine in a "Lash-up", the tender marker lights will go out because the interior lights are automatically turned off (for prototypical operation).  If you want them turned back on, you can manually access the Triplex engine from the engine list then turn the interior cab light on.


This is a minor sound file programming issue and MTH is aware of it. 








Hard to separate tender from engine (Tender Drawbar pin loose)


If you have any difficulty separating the tender from the engine because the drawbar pin seems to be too long, use a screw driver to ensure it's fully screwed in an tight.  If not completely tight, the pin can slowly work it's way out and increase the effective length of the pin resulting in your not being able to separate the tender from the engine.  If this happens to you, tip the engine and tender on it's side and screw the drawbar pin in, then you will be able to separate the two. 









Control issues with Triplexes running - Adding inductors to engines with a slave board


I have found that the engines running slave boards (Diesels with second powered A units, Triplex tender, etc) can affect signaling in some rare situations.  Under most normal situations users should not see any issues or change.


Any potential effects can be eliminated by adding an inductor in the + and - wires from the tender track power pickups leading to the slave board on each Triplex.  Use 100uh or greater.  


(Note:  Most users will not encounter such issues as they will be running on much smaller ovals, may have lights/SSBRDs deployed, and will be running with fewer engines [usually one at a time].  Also with the enhanced Rev L TIU and Protosound 3 boards this will even much less of a potential item.  This enhancement is to inform that if you are running multiple engines with multiple slave boards that this is something you can do long term to reduce the chance of a random control issue with an engine not responding.  This is not a must-do critical modification.)







Tender plug problem & repair:

See this link:  Tender plug repair





Power Pickup Sliders getting caught in switch frogs (Particularly #6 switches)

I haven't had slider issues with my Triplexes but for those having problems with their engine having a slider that dips in the frog which causes the engine get hung up or jerk, you will need to modify the slider just a bit. 

In some cases, the slider screw hole was not drilled perfectly straight up and down.  This results in the slider being tilted a bit front to back.  With the one end of the slider tilted down, that end will have a tendency to drop in the frog as it passes over and get hung up. 

The solution I came up with for this was to take and bend the slider pad to compensate and ensure the slider sits level on the track.

I first check to see if the slider is level front to back.  (The one in the photo here is already level)

Based on which end is dipped down, I know which way to bend the slider head to compensate. 

One way to fix is to take the slider off the engine and then use two pairs of pliers to bend the slider shoe pad so it is oriented correctly against the rail.   After you bend, reinstall it and check.  You may have to repeat these steps a few times to get it just right.  To speed this process you may be able to bend the slider with it on the engine by hand.


The other thing to check for is to make sure the outside edge of the slider is level as well.  If the outside end is dipped too far down it can get caught as well.  To tell if it's level, put the engine on it's side and look down the bottom of the drivers and see how the slider looks in comparison.  The slider inner to outer level should match.

This is level

This isn't.


If you still have a slider getting caught in a #6 switch frog, it's probably with the engine entering the main from the siding.  (see photos below)  If this occurs, you will need to take (likely with a pair of pliers) and bend the end of the slider that's dipping down in frog out just a tad.  So in this case below, the left side of the photo is the front of the engine, you need to make the front end of the slider bend out further to the left some. (Assuming the slider is already flat and level from the checks above).  Don't bend it too much and remember you are bending it out on the horizontal axis, you want to keep it flat and level.   Also, make sure the slider screw is fairly secure in the hole you may need to tighten it down some.

(Note: you may read where some have gone with the method of bending the outside edge of the slider way up to prevent it from getting caught.  This is not necessary if you go through these steps noted above.  If it's getting caught it's just out of adjustment by likely just a little bit.)


Once you have your sliders set right they will work reliably from then on, it's just a matter of getting any trouble sliders properly set which really doesn't take too much time.





Removing the boiler sub-frame - (For reference)

If you need to remove the sub-frame on the engine here are the step-by-step photos on how to do it.  


Remove screw

Remove screw

Loosen this screw

Then pull it out with piars. Don't drop it in opening into the steam cylinder or you will be fishing it back out.



You may have to push back on the top of the metal bar that goes up into the boiler to get the engine-set to separate.

The whole drive assembly can now be separated from the boiler.

Unplug this wiring harness

Remove screw

Remove screw

Remove plate then remove this screw

Remove screw

Remove screw

Remove screw

Remove screw

Remove screw

Remove screw

Remove screw

Remove screw

Remove screw

Remove screw

Remove screw

Remove screw

You may need to pull on the frame to separate it from the cab

Pull this pipe out of the side of the boiler

You're done

Note to see if this arm is on the replacement subframe if you are replacing yours.

Make sure the red wire matches to the + on the rectifier bridge and make sure it's all the way plugged in when reassembling.

Also make sure you plug the two pin component plug back in correctly when reassembling.


When reassembling, remember the material you are screwing into is plastic.  When the screw starts to get tight cut back on the torque.  Do Not Over-Tighten!!!





Smoking Whistle:  Instructions on how to activate:

Do the following steps to activating the smoking whistle:

       - Step 1:  Add 6 drops of smoke fluid into the whistle opening (remove the brass whistle first)

       - Step 2a:  Press "S2" (FSW) button - (This turns on the smoke whistle heater) 

                        - (Note:  You may need to scroll the softkey list with "S5" button to display SPW and FSW labels)

       - Step 2b:  Turn thumbwheel down - (This updates the screen to confirm FSW is highlighted/activated)

       - Step 3a:  Press "S1" (SPW) button - (This turns on the Whistle Quill feature)

       - Step 3b:  Turn thumbwheel down - (This updates the screen to confirm SPW is highlighted/activated)

       - Step 4:  Rotate the thumbwheel up to activate/increase whistle (Three steps of quill are available).  Rotate thumbwheel down to deactivate/decrease whistle.

                        - (Note:  If you see smoke coming out the bottom of the boiler and not the top, blow in the top of the whistle hole to clear any fluid bubbles and retry)



Step 1:

Step 2a:

Step 2b:

Step 3a:

Step 3b:

Step 4:






Charging the engine's PS2 on-board battery:

See this link:  Charging engine PS2 battery





Polarity switch location:

This is the location of the polarity switch on the Triplex.




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