Huawei Y300 Maintenance Manual page 61

Y300 Maintenance Manual
Troubleshooting
Fault symptom: The Y300 can be powered on, but the LCD displays nothing.
Handling: Check the LCD. Troubleshoot the fault according to the process shown in Figure
9-33.
Figure 9-33 Troubleshooting process when the LCD displays nothing
Circuit Symbols
Signal Symbol
VREG_ 2V85_LCD
VREG_S3
MIPI_DSI_LANE2_P
MIPI_DSI_LANE2_N Differential signal (–)
MIPI_DSI_LANE1_P
Issue 1.0 (2013-01-24)
The LCD displays
nothing.
Is the fault
rectified after
you replace the
LCD?
N
Is the
backlight
lightened?
Y
Is the J1302
properly
soldered?
Y
Is the U401
properly
soldered?
Y
Return the Y300 to
Huawei for repair.
Description
LCD analog voltage
I/O digital voltage
Differential signal (+)
Differential signal (+)
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Y
End
N
Check the
L1310 and
U1303.
N
Re-solder the
J1302.
N
Re-solder
the U401.
Reference Measurement or
Waveform
2.85 V
1.8 V
1.8 V
1.8 V
1.8 V
9 Principles and Failure Analysis
56