7861 - Lighting Set Electric 12V
The grey era came with a great number of track options and accessories. Most of them, like this 7861, were released in 1980 and were available all the way to 1990.
Of all the grey era train sets, only three were equipped with lights: 7740, 7745 and 7750. But LEGO offered this little upgrade kit, allowing two trains to be equipped with working headlights, powered from the conducting rail through the 12V motor. The set contains four light bricks, four cables and eight prisms with four matching prism holder bricks in black and red. Usage wasn't restricted to trains and wagons, the set could also be used to illuminate buildings.
Early versions of the light bricks have only 2 plug holes and smooth glass, while later versions have an additional center hole and diffuse glass. The set came with at least two different instruction booklets. One shows how to upgrade set 7725 (1981-1984) while the other shows how to upgrade set 7735 (1985-1990). As set 7725 was released only in 1981, there must be a third version that reflects year 1980.
This set is yet more evidence of how LEGO ran the system approach. You could start with a push-along train and then start upgrading with a 12V motor and lights. Some sets are very well suited for the lights kit, without changing the look (7720, 7725, 7730 and 7760). Other sets require more extensive modifications and change the look significantly (7710, 7715, 7722, 7727, 7735, 7755 and 7810).
Packaging (3D scan)
From 1980 to 1988, the box was made of styrofoam with a cardbox sleeve. From 1989, the box was redesigned without styrofoam.
version 1 (1980-1988)
click to view the 3D scan