BBK DV718SI, Руководство по обслуживанию, Страница: 25 / 120

When reading VCD disc, laser power becomes weak, voltage of MDII pin decreases, voltage
decrease of pin 23 of MT1389 makes voltage of pin 19 of XS301 increase to reach the purpose of raising
laser power. When laser power is too strong, voltage of MDII pin increases to lead to voltage of pin 23 of
MT1389 increase to make voltage of pin 19 of XS301 decrease to reach the purpose of reducing laser
power to form an auto power control circuit.
When reading DVD disc, pin 21 is detect signal input pin, pin 22 is drive control input pin, and the
working principle is the same with that when playing VCD disc.
3. Key point voltage (unit: V) is shown as the following table:
Location number Read DVD disc Read VCD disc Location number Read DVD disc Read VCD disc
V103_E 2.9V 3.2V V104_B 3.2V 2.2V
V103_B 2.2V 3.2V V104_E 3.2V 2.9V
V103_C 2.2V 0 MT1389_20 0.2V 0.2V
V104_C 0 2.2V
3.2.5 Open/close door drive circuit
1. Open/close door drive circuit is shown in the figure 3.2.5.1:
2. Working principle: when machine is reading disc normally, pin 6, 7, 9, 10 of AM5888S is 0V. After
pressing OPEN button, pin 6 inputs high level, pin 10 LOAD+ outputs high level, electric machine rotates
positively and performs the action of opening door. When closing door, pin 7 inputs high level, pin 9
LOAD- outputs high level and forms loop to pin 9 through electric machine, electric machine rotates
reversely and performs action of closing door. After closing to proper position, all pins are low level.
Servo drive principle is the same with that of D5954 solution, so we will not introduce here.
R203
27K
R204
27K
R202 15K
LOAD+
TRCLOSE
TROPEN
R314
10K
TRSO
STBY
SL+
SL-
FMSO
SP-
SP+
FOSO
DMSO
TK-
FC+
TK+
FC-
V1P4
LOAD-
R201
10K
AM5888S
MT1389
Figure 3.2.5.1 Open/close drive circuit diagram
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