The intermediate design color scheme (mellomdesign in Norwegian), was introduced in 1981 and only lasted a few years. 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. As I was able to get another copy of this model I decided it to renumber it to Di3.641 and give it the full DCC sound treatment.

The original Di3.643 model. It will be completely taken apart. Then the masking starts around the number.

A few years ago I found out that airbrush thinner was an easy way to remove the old Heljan numbers. Applying a small amount with a Q-tip (cotton swab) and a little bit of rubbing and the old number dissapears without a trace. Then the new number (Di3.641) will be applied.

The Heljan models are known for having poor wheel conductivity and therefore a power pack is a must in these locomotives. For this install I've used the Train-O-Matic SPP. The power pack is installed in the diesel tank under the frame. A small whole is drilled in the frame for the wires. To do this the motor has to be taken out.

An ESU Loksound 5 DCC with an iPhone 4 speaker are being installed. The wires of the power pack are coming up from behind the PCB and are connected to decoder.

The end-result. A NSB Di3.641 in mellom design, as it ran from 1982 to 1987.