From BR Training booklet:

DC Generators and Regulators

Regulators Battery Charging Diode Type
Maintenance:

1.	Remove cover and check safety chains, check cover seals
2.	Remove battery isolation link
3.	Remove carbon pile and connections
4.	Visually examine carbon pile and connections
5.	Visually examine all cable connections
6.	Check VSR and VDR settings
7.	Check fuses
8.	Clean all components
9.	Replace cover

Generator
Maintenance:

1.	Remove cover carefully and check for copper of solder particles on cover
2.	Visually inspect brushes for condition and length (1 1/4in 32mm)
3.	Check brush box assembly will rotate through ninety degrees
4.	Check flexible connections for security and insulation
5.	Check for loose or broken terminal board
6.	Visually examine comutator
7.	Blow out with dry compressed air

Fault Finding:

1.	Check for missing or slack belts
2.	Carry out examination as per depot service
3.	Check field fuse and output fuses (located in dynamo coupling box)
4.	Check battery box fuse
5.	Check circuits of panel
6.	Check for battery charging diode breakdown