Huawei G700-U10 Maintenance Manual page 72

G700-U10 Smartphone
Maintenance Manual
Circuit Analysis
The key circuit is simple because only three keys (power, volume up, and volume down) are
used on the G700-U10. Each key is controlled by a signal. When a key is not pressed, its
control signal is at high level; when it is pressed, the control circuit is short-circuited to the
ground, and the control signal changes to low level. Serving as the bearer of the volume up
and volume down keys, the volume key FPC connects the keys to the CPU through the ZIF
socket.
Troubleshooting Process
Figure 10-40 Troubleshooting key failures
Circuit Signals
Table 10-11 Circuit signals of this section
Signal
PWRKEY Power-on and power-off
KCOL1
KCOL0
Issue 1.0 (2013-07-22)
Key failure
Is the side key
FPC normal?
Y
Is the ZIF
connector normal?
Y
Resolder or
replace U401
Description
signal
Volume up
Volume down
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N
Replace the side key
FPC
N
Resolder or replace
J1502
Reference Value or Waveform
Default: high level
The level is low when the power key is
pressed.
Default: high level
The level is low when the power key is
pressed.
Default: high level
The level is low when the power key is
pressed.
10 Circuit and Failure Analysis
67