8-7 BRUSH
The brushes must be smooth where they contact the slip rings. If not, polish smooth the brushes with sandpaper. A brush that is not smooth produces arcs between the brush and slip ring leading to possible damage. Usable brush lengths are from 5 mm to 15 mm (0.2 " to 0.6").
A brush shorter than 5 mm must be replaced because decreased contact pressure between the brush and slip ring lowers gen- erator efficiency and output voltage.
BRUSH
HOLDER 
15 to 5 mm
(0.6" to 0.2")
BRUSH
8-8 A.V.R
(AUTOMATIC VOLTAGE REGULATOR)
1) Features
This AVR operates to control the field current in order to maintain the output voltage for the AC current, which generated by the magnetic flux by the field coil.
2)A.V.R. trouble may be identified by simply looking at the A.V.R., or by the
2
4
1
3
Terminal number of the A.V.R.
Yellow
(a)A.V.R. TROUBLE IDENTIFICATION by APPEARANCE
If an A.V.R. electronic part is burnt dark, or the surface epoxy resin melted, it often indi- cates A.V.R. trouble.
(b)IDENTIFYING A.V.R. TROUBLE by CHECKING
Check the
NOTE : Take teater inaccuracy into account in reading the tester.
(c)IDENTIFYING A.V.R. TROUBLE by MOUNTING and OPERATING in THE GENERATOR SCR or transistor damage cannot be detected by simply looking at the A.V.R. or checking the lead resistance. Check it by mounting the suspectedly faulty A.V.R. in a normal gener- ator, or mount a mormal A.V.R. in a generator which fails to generate voltage.
