Between 1977 and 1979, the South African Railways placed 150 Class 6E1, Series 7 electric locomotives with a Bo-Bo wheel arrangement in mainline service.

[1] The 3 kV DC Class 6E1, Series 7 electric locomotive was designed and built for the South African Railways (SAR) by Union Carriage & Wagon (UCW) in Nigel, Transvaal.

A pantograph hook stick was stowed in a tube mounted below the lower edge of the locomotive body on the roof access ladder side.

While some Class 6E1 series are visually indistinguishable from their predecessors or successors, some externally visible changes did occur over the years.

[4] Late-model Series 7 locomotives were equipped with side doors on which the outside door latch handle was mounted near floor level with a simple drawer pull type handle at mid-door level.

Since there was no guarantee that another train would be in the same section to absorb the regenerated energy, there was always the risk that line voltage could exceed 4.1 kV which would make either the sub-station or the locomotive trip out.

1 end was stripped of all controls and the driver's front and side windows were blanked off to have a toilet installed, thereby forfeiting the locomotive's bi-directional ability.

The fact that the handbrake was located in cab 2 was not a deciding factor, but was considered an additional benefit.

In the 1990s many of the Series 6 units began to be repainted in the Spoornet orange livery with a yellow and blue chevron pattern on the cowcatchers.

In the Passenger Rail Agency of South Africa (PRASA) era after 2008, at least one was repainted in the Shosholoza Meyl purple livery.