Brushes; Avr (Automatic Voltage Regulator) - Robin LG072 Service Manual

9 - 2 - 2 MEASURING INSULATION RESISTANCE
Refer to
8-4 MEASURING INSULATION RESISTANCE.
9 - 2 - 3 CLEANING SLIP RINGS
The slip ring surfaces must be uniformly bright. Slip rings
showing black spots, excessive wear, or uneven wear must
be repaired. A stained slip ring lowers generator efficiency
and output voltage. Polish the slip rings with fine sandpaper
while turning the rotor until rough spots disappear. Care
should be taken not to touch the rotor coils with the sand-
paper. (See Fig. 9 - 3
.)
9 - 3 BRUSHES
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 possibie damage. Usable brush lengths
are from 5 mm to 15 mm as shown in Fig. 9-4. A brush
shorter than 5 mm must be replaced because decreased con-
tact pressure between the brush and slip ring lowers genera-
tor efficiency and output voltage.
Fig. 9-3
f
i 1 5 m m - 5 m m 1 5 m . m - 5 m
Fig. 9-4
9-4 AVR (AUTOMATIC VOLTAGE REGULATOR)
AVR trouble may be identified.by simply koking at the AVR, or by checking the inter-lead resistance with a tester, or actu-
ally mounting it in the generator and operating it.
9 - 4 - 1 AVR TROUBLE IDENTIFICATION
by
APPEARANCE
If an AVR electronic part is burnt dark, or the surface epoxy resin melted, it often indicates indicates AVR trouble.
9 - 4 - 2 IDENTIFYING AVR TROUBLE
bf
CHECKING
INTER-LEAD RESISTANCE
Check the inter-lead resistance of the AVR with a tester.
(See Fig. 9-5.) If the tester readings vary greatly from the
values specified in the tables below, the AVR is faulty.
NOTE: Take tester inaccuracy into account in reading the tester.
TESTER
Fig.
9-5
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