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c.
Check if RAM, Flash and peripheral components are well welded, if Flash card data
lost or if reprogram Flash.
3. No Display of LCD
Confirm the current is normal the equipment is started. If LCD has no display when
connected, do investigation by following the steps below.
a.
Firstly check if voltage of VCC_LCD (3.0V+/-0.1V) is normal,
if abnormal, check U19 and surrounding circuits.
If normal, the system startup is normal, please check backlight IC(U22) and surrounding
circuits.
b.
Connect the LCD and then check backlight driving circuit.
c.
If the system cannot be started after confirming that relevant components of the CPU,
memory and Flash are well welded, please consider replacing Flash, CPU and
memory.
II. Functional Fault Checking
1. Failure of Charging and Power Detection
Abnormal charging: For charging failure when DC is applied, check whether the welding
of U85
2611 charging IC peripheral components are good,whether the battery is
damaged, whether the surrounding circuit is normal.
Abnormal DC insertion check (software shows battery power supply when DC
power is inserted): Confirm first DC 5V has a voltage of around 5V,and then check if
is well welded.
The equipment does not work with battery power supply (but work with
external power supply): Without external power supply, check if the voltage of VSYS is
normal and if the circuit of PMU part is normal.
2. Abnormal Operation of USB and USB Peripheral
Detection failure of USB insertion: While connecting MID with PC via USB cable,
USB insertion cannot be detected. Check mainly the circuits of USB-DET, R53 R56 Q7
are well welded.
OTG dysfunction：Confirm if VCC-OTG has a voltage of around 5V when OTG
cable inserted. Confirm if OTG-ID voltage is at a low level. If the voltage is lower than
5V, check if U16 well welded.
3. Abnormal LCD Operation
Abnormal LCD backlight：
LCD backlight does not work：Check if the circuit of Part U22 in normal operation.
Nonadjustable LCD backlight brightness: Check if the circuit of Part U22 is
normal.
Abnormal LCD color display:
Check if LCD extension cords are well welded, if circuits of U19 and surrounding
parts are normal.
Touch screen abnormity:
Run touch screen calibration program and then check if it is normalized.
U85
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