The Di3.621 has been made in HO by both Heljan and NMJ. Both models are in the red colors (ny design). The original NMJ model has no top lights above the cab, this is putting the model in very early 1984.

Somewhere in 1984 cab 1 got a top light, but the horn wasn't moved yet. See Di3.621 in September 1984 for a picture of this version.

In 1987 the horn was moved to the roof and cab 2 got a top light as well. See photo from Bjørn Næss on the NJK website.

In 1990 cab 1 was isolated and it got panserglass. As part of this the horns were moved further down the roof and it got a small antenna on the top of the roof.

Heljan made a model (together with Bergen Modelljernbane) of this latter version, as it was in service until 2000.

I was interested in making a model of the version that could run from mid-1987 to early 1990. This page is about that conversion.

The result of this conversion, three versions of the Di3.621:

• Original NMJ model (early 1984)
• Modified NMJ model (mid-1987-1990)
• Heljan model with isolated cab (1990-2000)

I was able to buy one of the NMJ Di3 models that were painted in the wrong red color in early 2020. The first photo shows the 626 which has a darker reddish color, which is incorrect. The shell of the 621 show the right color.
The middle photo shows the wiring of the top light in the 626 after the removal of the cab interior. To be able to remove this carefully I stripped the cabs from all its parts.

The last photo shows both shells, stripped of parts around the windows. In this photo you can clearly see the color difference between the two shells.

Cab 1 of the 621 has all the parts and the new top light. It is shown here with a photo of the original in the back.

At this time I was still awaiting an answer whether cab 2 had the light or not but I got the answer later in the day.

The final result on the layout, a NSB Di3.621 representing the late 1980's. Both cab 1 and cab 2 have the top light but cab 1 isn't isolated yet.