Insert a valid SIM card after the
boot does not open the Internet
Signal display, check
the main transmission
channel
Check the transmission
circuit matching circuit
device is bad
Check whether the
normal UI RF power
amplifier
The transceiver chip
U600 (MT6166), the
CPU is damaged.
To replace or re
welding transceiver
chip U600
replace or re bad
welding device
If there any signal
No signal display, check
the circuit of RF system
Check the matching circuit
components have break or weld
Check U616, U607 are
normal.
The receive path reference
emission pathway
END
Check the antenna contact
and the PCBA antenna feed
point contact is good
Finishing cleaning
antenna, PCBA
antenna feed point
Y
Y
Y
Y
Y
N
N
N
Y
Y
N
Y
Y
N
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