Class 73 had a simpler electrical system arrangement for control of the dual power sources - even to the point of two separate power controllers on the driver's desk; one for diesel and one for electric. The complex control system of Class 74 (with a single dual-purpose controller) was problematic and the class was dogged with electrical system failures up to their last days. Together, the three complaints of poor reliability, difficult engine starting and excessive noise made Class 74 unpopular with crew and fitters alike.