Marshall DSL100H @shroprockdoctor for repair of an…

Marshall DSL100H @shroprockdoctor for repair of an unspecified fault.
Powered up via variac the fault presents as a loud hum through the connected speaker.
All fuses intact.
Owner has apparently installed new valves which as can be seen in the image we’re all incorrectly seated in the bases.
Valves are now correctly installed but the fault remains with the power level switch in both positions (full & half power).
Ended the day retrieving the schematics for this 2012 revision of the DSL100.
Tomorrow begins with some probing with the multimeter.