HuaWei Mate 7 Telecom Standard Version No Current At Boot

HuaWei Mate 7 Telecom Standard Version No Current At Boot You had to approval this situation that the mobile is becoming the computer that fits in your hand or your pocket. And while it doesn't look like your desktop or laptop, just like those devices, sometimes you need to start at any time, so we will come across the boot problem. Now I will introduce the solution that the Huawei Mate 7 boot without current, hoping you can benefit from it.

Phenomenon Description: The mobile phone power on by programmable power supply, when we hold down the switch button, the current don't have change. Generally, for HuaWei Mate7

boot without current fault, the reason mostly is PMU output short circuit, but sometimes maybe VBAT(SYS) short to ground. Now this phone fault is not for the above reasons, but caused by BUCK_BOOST no voltage output.

The Process of Analysis and Reapir: 1. Maintenance ideas The mobile phone boot without current fault ask to measure the voltage of each line, secondary system is it normally. You need pay attention to the RTC circuit abnormal is not caused the mobile phone boot without current fault.

2. Repair process a. Insert the charger into charging port to provide electricity, measure the L1501 voltage is 4.2V, so from this decision, the VBAT(SYS) is not short circuit and the voltage is normally. b. Measure the 6 routes VBUCK line of U1000 output has not voltage, it means the PMU output is abnormal. c.

Measure

the

VOUT_PMUA(C1018),

VOUT_PMUD(C1019) hasn't voltage, the diode value is normally. Then measure the VCOIN(C1013) hasn't

voltage, the diode value is normally. d. All above is not the mobile phone fault reason, it means the fault is hidden deep. We back to the origin, check the exterior, then take off the U2002 foam and find it damages a little, finally find a breakthrough.

e. Measure the U1100 output voltage is 0V, but the OK board is in this state that does not press the power button on the power, the U1100 output(C1122) has 1V. The C1122 diode value is normal, so can't make sure to boot the the PMU or U1100 first. So ask help for Jass, it said that after normal power on, the BUCK-BOOST is boot first, after 5mins the LDO-PMUA will establish an internal quasi base source, simple speaking, after the U1100 normally output BUCK_BOOST voltage, the PMU will boot normally.

Solution: Replace the U1100 and retest, the fault has been removed.

Experience Summary: When we repair a fault phone, we can't disassembly or replace the parts or motherboard blindly. Every welding will shorten the life of motherboard, if you don't know how to repair next, you should ask help with your colleague.