USB not connected
whether
5V of L18 is normal;
whether grounding is
normal
Whether 3.3V, 1.8V
are normal
check
resistor to ground of
D+, D-
Change audio decode
IC PNX0101
Q8 has trouble or USB
socket has false welding
Check each DC-DC switch
circuit and peripheral elements
Check whether T1 or USB
socket pin has rosin joint
Change crystal oscillator or
capacitor on two sides
N
2. Troubleshooting process for “USB not connected” is shown in the figure .3.3.2.2:
Y
N
Figure 3.3.2.2 USB jack troubleshooting flow chart
whether
oscillation of 12M
crystal oscillator is
normal
Y
N
Y
N
Y
- 31 -
Summary of Contents for X21
Page 1: ...service manual X21 RU ...
Page 42: ...3 L1 1 8V energy storage waveform diagram 4 LCD_CS wabeform 5 LCD_D C waveform diagram 37 ...
Page 43: ...6 LCD_RESET 7 LCD_WR waveform diagram 8 LCD_RD waveform diagram 38 ...
Page 45: ...12 LCD_DB3 waveform diagram 13 LCD_DB4 waveform diagram 14 LCD_DB5 waveform diagram 40 ...
Page 46: ...15 LCD_DB6 waveform diagram 16 LCD_DB7 waveform diagram 17 IREF waveform diagram 41 ...
Page 47: ...18 VCOMH waveform diagram 42 ...
Page 66: ...Chapter Cinque PCB board Circuit diagram Section One PCB board X21 PCB Board 61 ...