Powerline models T-class decoder replacement


I have recently visited Austrailia, where I decided to buy a model train for my collection. The model train I ended up buying was a T-class from Powerline models with running number T373 (PT3-7). The production date of this locomotive is around 2008. T-class locomotives produced in that time comes with a DCC decoder pre-installed. That decoder have a switch where you can toggle between DC and DCC operation, set to DC by default. Bellow is a picture of the decoder.

The problem with this decoder is that I couldn't get it to work with my Roco multiMAUS or the more recent Z21 control system. I could get it to jump and short my entire layout if I switched it to DC operation with the multiMAUS.

I therefor decided to replace the entire decoder. There where three options that i considered.

Only the first decoder in the list where available to order directly where i live. The problem with that decoder is that its difficult to install without having to extend the cables. My inexperience with soldering and lack of proper tools made that decoder a bad option for me. I therefor contacted a hobby shop in my country to ask if they had any recommendations and mentioned the two other decoders. Their reply told me that they where willing to special order any of the two other decoders.

The problem with the ESU direct decoder was the length specified in the data sheet. Some of the wires in the model is quite short, meaning that I might have to extend the wires if I choose the ESU decoder. I therefor endend up ordering a TSU-PNP8 DCC sound decoder, as that decoder had the same length as the factory-installed decoder.


I used the following tools for the decoder replacement.

Soldering iron (15W, 400 °C)
Flux, liquid
Tip activator
Soldering brass
Desoldering pump
Soldering stand
Soldering mat
Screwdriver PH1 x 50 mm

You really only need a PH1 screwdriver, soldering iron, solder and flux to do the decoder replacement, but all the other mentioned tools is extremly helpfull if you somehow mess up. You need the desoldering pump if you need to undo something that went wrong. Tip activator is also required if you are unable to tin your soldering iron.

Removing the decoder

Most of the factory installed wires where held in place with plastic housing. The exceptions where the motor wires, which where soldered.

The wires are connected from the factory according to the table bellow.

Front of the decoder
T- Current pickup Black wire
FL Headlight Blue wire and red wire from rear
V+ Headlight White wire
T+ Current pickup Red wire
Rear of the decoder
T- Current pickup Red wire
RL Taillight Blue wire and red wire from front
V+ Taillight White wire
T+ Current pickup Black wire
Side of the decoder
M+ Motor Red wire
M- Motor Black wire

Installing the new decoder

Its important to be aware of the differences between the decoders when it comes to the connection terminals. I messed up the wiring the first time, since I didn't pay enough attention to the terminal markings. The bellow picture shows the difference between the decoders.

We can see from the image that the V+ terminal have switched place with the function output 0 (F0, lights front and rear).

Another difference is the terimnal connections. The terminals on the Tsunami decoder is too narrow to fit the plastic housing. I therefor had to solder the wire to all of the terminals. Flux was used to make sure that the solder ended up where I wanted it to be. The tip activator was used so I could get the solder to stick to my soldering iron.

Bellow is an image of the end result after soldering. I did damage the coating of one the motor wires, but it didn't cause any issues for the initial tests.

Testing the model

The TSU-PNP8 will light up blue to indicate power.

One strange issue that I encountered with the model was that the rear white lights would turn on whenever I put power to the layout. The even stranger thing was that it only happend when the train was fully assembled. The issue seemed to be related to the wiring getting squeezed whenever the shell was on.

The way I mitigated the issue was to make sure the wires where properly laid. Bellow is a picture of proper wiring in the rear. Note how the wires are laying down in its pathway, not on the outer edge.

The same applies for the front. There are pathways for the wire there also.

I have published a YouTube-video showing the locomotive after finishing the decoder installation.

Next steps

I choose to not install speakers at this time, even though I installed a sound decoder. I might at some later time add in a speaker. The challenge with speaker installation in this model is the cramped space, so finding a good way to install sound might be difficult.

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