Breakdown phenomenon
After IPhone7 is thrown, switch on the mobile phone appear without service breakdown.
Maintain a course
The possibility of solder of empty of part of the base band after IPhone7 is thrown is larger. Repair confidential of hand of this kind of breakdown to foster cordial relations between states base band part first,
Consider other issue again next.
To take roundabout way less, measure the working requirement of base band first. Measure the part of LDO power supply that chip of base band power source exports first
(See a picture) 2 extremely system value. Discover LDO power supply through measuring 2 extremely body is worth as good as constant.
The S1~S5 power supply that measures output of chip of base band power source next (see a picture) 2 extremely system value, judging these power supply is
Deny unusual.
Should measure S5 power supply 2 extremely when body is worth, discover S5 power supply 2 extremely system value is 0, 0 express short circuit. Basis before
Maintenance experience is informed capacitance C5618_RF to damage easily (see a picture) , pull down capacitance C5618_RF directly so.
Pull down after capacitance C5618_RF, switch on the mobile phone into system testing, firmware saw in the modem firmware about this machine
Version, the specification has identified base band, but the top left corner of mobile phone screen still hints " without the service " .
Chip of big in IPhone7 discovers when be being maintained before radio frequency and chip of small radio frequency (see a picture) easy attaint, can cause
Without service breakdown.
After trading chip of big radio frequency and chip of small radio frequency directly, switch on the mobile phone enter system testing, mobile phone top left corner shows Chinese UniCom is mixed
4G icon, the specification has had signal, if plan institute is shown, check other function to all be not had unusual. Maintenance comes here end.
