The Norwegian Di3 has had many different color schemes. The early versions were delivered in green. In the 1960's they all became brown with a yellow stripe. This is nowadays known as 'gammeldesign' (old design). In 1981 a short-lived color scheme was introduced, where the locomotive was painted red but the logo and number stayed in the old yellow style. Two years later the color scheme changed again to a red color with white logo and numbers (nydesign). The short-lived design has gotten the name 'mellomdesign', meaning intermediate design in Norwegian. Only 5 Di3 locomotives were repainted in this color scheme; Di3.604, Di3.606, Di3.607, Di3.641 & Di3.643.

Heljan made a model of the Di3.643 in mellomdesign (catalog no: 4342). I have this model in my collection since 2004. Originally I just plugged in an 8-pin decoder but later on I did install sound decoders. First a TCS WOW (version 1) but eventually settled on a Loksound Select.
It is time to make some upgrades and this page is all about this upgrade.

The Heljan model in the original box. In front are some new parts; A Train-O-Matic SPP (Power pack), a replacement diesel tank and an iPhone speaker.
The second photo shows how I placed a TCS speaker in the diesel tank. This looked like a good idea but in reality the sound is poor and since the core of the speaker is a magnet it attracks small metal parts from the layour. The last photo shows the internals with the shell removed. This model has been used to test various decoders, this is a Loksound Select, which I will keep for this upgrade.

I will use a different speaker, an iPhone speaker. I prefer to have a power pack installed and I will place this in the diesel tank. As I used a different Heljan model as parts resource, I could use that diesel tank. To guide the wires, I drilled a hole under the motor. The last photo shows the hole in the frame with the three power pack wires. The iPhone speaker is soldered to the two speaker leads from the ESU Loksound Select decoder. The power pack used is a Train-O-Matic SPP.

This photo shows the three power pack wires coming from behind the motor (next to the motor wires) and connected to the decoder.

As I'm going to do a light upgrade as well, some modifications were made to the Heljan PCB. At the location of the red arrows the PCB traces were cut so that one pin of the "R" connector is fully isolated from the PCB board. A black jumper wire was needed to loop around the cut traces.

The early 2000 generation of the Heljan NOHAB models has a single light bulb on each side of the model. Dansk Hobby built a LED replacement set and that is what I will install. By default this replacement will provide 3 lights on the front and 2 red on the rear. This might be prototypical for a Danish NOHAB but not for a Norwegian NOHAB. Therefore I will modify the light boards.

The existing light fixture in the shell needs to be removed and three small clear lenses are to be installed. This photo shows the original light fixture removed and the three new lenses.

The LED boards from Dansk Hobby will be modified. To start with, the top led traces are cut, you can see the small cuts in the corners of the PCB. This makes the top LED completely isolated from the bottom two LEDs. Then a bridge wire is connected across the board. The top LED will get a SMD 4.7K resistor, just like the other LEDs and then a jumper wire. The second/middle photo shows the result of these modifications.
Then the board is installed in the locomotive. The top LED is connected directly to the decoder (AUX1 & AUX2). I've kept the red LEDs and connected them to AUX3 and AUX4.

These modifications allow for the bottom to lights to work independently from the top light. The programming is done according to my ProtoThrottle function mapping.

The end-result, just before the shell is put back on the frame. Compare this with one of the original photo's on this page. The decoder and speaker are tied to the board with kapton tape.

The end-result. The Di3.643 in mellomdesign with the bottom headlights on. Next to it, is the Di3.641. See Heljan Di3.641 DCC install for more details. Both the 643 and 641 were painted in mellomdesign in 1982 and then repainted to the red color in 1987.