Section Three Servicing Cases
3.3.1 Servicing cases
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]
Example 1 Symptom: power-on protection
Description: after power on, relay does not attract and "system abnormal, auto protection" displays.
Analysis and troubleshooting: after power on, system protects, relay does not attract, shown as in
the figure 3.3.1.1; test L, R, C, SL, SR of power board flat cable holder XP8 and there is no DC output,
test pin 1 of power board flat cable holder XS7 and it is high level, pin 2 is low level, C electrode of triode
V101 is high level; it is known from the above test that the protection is not caused by over-current and
over voltage (you may also unplug flat cable holder XP7 and XP8 and check whether it has protection).
Test positive voltage of diode VD112 and it is 0. We judge that relay has trouble. After changing relay,
trouble is removed.
Figure 3.3.1.1 Protection circuit diagram
Note: 1. After relay is used for a period, working state may be unstable and some abnormalities may
appear: relay does not attract after power on sometimes; each contact point does not touch fully after
relay attracting sometimes; CPU cannot detect RLY0 signal (after relay attracting this signal is low
level), auto protection.
R106
4.7K
C110
220u/35V
R115
4.71W
R114
4.7/1W
R113
4.7/1W
R111
4.7/1W
R112
4.7/1W
C1160.1u
C1170.1u
C1180.1u
C1190.1u
C1200.1u
C115
47U/25V
R108
100K
R107
100K
VD110
IN4148
VD111
5.1V
R110
56K
11
3
7
12
4
8
13
14
9
1
5
10
2
6
Y100
RELAY-4
VD112
1N4148
RLY0
1
2
XL101A
WP6
1
2
XL101A
WP6
1
2
XL100A
WP4
1
2
XL100A
WP4
1
2
XL101A
WP6
SWM
V105
C9014
V104
C8050
V103
C9015
RLY0
SWM
1
2
3
4
5
6
7
8
9
XP8
CON9
VC-
VC+
L100 0.7UH
L101 0.7UH
R117
51K
R118
47K
R119
47K
R120
47K
R116
51K
R105
10K
V101
C9014
V102
C9014
R104
10K
R102
1K
R103
47K
R101
1K
VD108
IN4148
C114
220u/16V
C113
220u/16V
R109
10k
R100
47/3W
V100
C9014
1
2
3
4
XP7
CON4
SWM
RLY0
P_RC
OVER
L2
R2
C2
SL2
SR2
GND
GND
VC-
VC+
C121
103
VD113
1N4004
C122
104
C126
103
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Summary of Contents for AV311T
Page 1: ...service manual AV311T...
