Huawei YU220 Service Manual page 60

U301 keyboard lighting is by issuing an enable signal GPIO_KPLED_EN
makes transistor Q1001 is turned on, then the three keyboard lights.
Firstly judge the keyboard light paster whether have problem, dry joint or
short circuit, or reverse weld problem, it need to affirm welding series
resistor whether unusual if the light have no problem.
Finally, whether the transistor is installed is damaged, or does not turn-on
voltage。
Finally, whether the enable signal when the keyboard light should not to be
pulled, not pushed, it indicates a problem U301, U301 can be changed
again.
2013-10-18
YU220 service manualV1.0
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