Saturday, August 6, 2016

TOMIX Usui Pass (碓氷峠) EF63 DCC conversion

Some time ago I won both TOMIX EF63 locomotive tandem models in an auction at a very good price. It's item number 92908, decorated in brown color, and 92123 decorated in blue. Seem to be special models as they are come in a beautiful case. Notice that one of the engine models ends with "T", while the other ends with "M". Only "M" locomotive is equiped with Motor, while "T" locomotive is only a dummy.

The Usui Pass (碓氷峠 Usui-tōge) is a mountain pass that lies between Nagano and Gunma Prefectures in Japan, near to Karuizawa city. It has served as one of the major transportation routes in central Japan since at least the eighth century and Shinetsu main line was crossing it. Due to its high gradient, banking engines where needed in both ascending and descending. That was the job of these EF63 models.

Tomix models are for me the best detailed ones, but on the other hand are the most difficult models to convert to DCC. Normally is difficult to find room enough for the decoder, and access to the motor is also complicated as the pick up current plates are not accessible unless you disassemble it completely. This is the case:

Each locomotive only has lights, and its respective light board, in one of the sides. Taking a tiny decoder (D&H DH05 in my case), you can place it in the space of the missing light board and you won't need to sand any locomotive's part.

My plan is also to replace the bulb light in the board with a led light. Only the red light uses a led:

First of all you have to perfectly isolate the motor engine and solder the gray and orange cable there, like any other similar Tomix model. Wires fit in the space between the two metal blocks where motor is enclosed in. I recommend you to use Kapton tape, normal tape is too thick for this.

The only tricky part is the light board. Taking a look to the original board we want to keep the resistor and existing red led, remove the bulb light and associated components (diodes), and add a white led using also the same resistor for it to do not add more components as the room is imitated. Positive lead will be connected directly to the rail current, and negative lead will be connected to the white and yellow wires of the decoder. As the board has pick up current tracks, I plan to use it also for the red and black wires of the decoder as is impossible to solder something directly to the lead pieces:

This is how I prepared the light board, removing the SMD components of the bulb and the bulb light itself, and soldering the white led. The point where I soldered it is isolated but will fix the led in place. That's why I added a wire to the positive lead of the other led. Negative lead of each led will be isolated and connected to the white and yellow decoder cables:

And that's the result once in place:

First tests worked fine, with no short circuits. Take all the time you need to make sure decoder, motor and function cables are not in touch with the rail current (lead blocks) or your decoder can burn in the first test.

I thought the most tedious job was done, but I spent even more time detailing with the accessory parts both locomotives:

outlets, hose connectors

Horn? Antena?

This antena needs to drill the holes


These locomotives run in a really smooth way, and once detailed they are really beautiful. I hope you found this tutorial useful.

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