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G700-U10 Smartphone
Maintenance Manual
Troubleshooting Process
Figure 10-57 Troubleshooting USB detection failures
Circuit Signals
Table 10-19 Circuit signals of this section
Signal
VBUS
USB_DM USB data (+)
USB_DP
KCOL0
Issue 1.0 (2013-07-22)
USB failure
Is the USB port
properly soldered?
Y
Are the surrounding
components of the USB port
properly functioning?
Y
Resolder or
replace U401
Description
USB power supply
USB data (–)
USB download triggering
signal
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N
Resolder the USB port
Resolder or replace the
N
surrounding
components
Reference Value or Waveform
The voltage is 3.3 V.
High-speed digital pulse signal
High-speed digital pulse signal
When KCOL0 is grounded, the system enters
USB download mode.
10 Circuit and Failure Analysis
83
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