Lenovo G360 Does Not Power On

 

Laptop Model: Lenovo G360 Quanta LL7

Fault : Laptop Does Not Power On

Maintenance process:

 

When the maintenance power supply is connected, the trigger jumps from 0.004 to about 0.016. Some people may think that this is a trigger because the current has jumped, but what I mean is that it is generally not a trigger until the SLP_* signal is set high. 

I thought it must be that the conditions on PCH are not met. I usually have two ideas about this problem: the first is to check whether the CMOS battery has power. If there is no power, most of them are VCCRTC, RTC_RST#, SRTC_RST#, Caused by SM_INTRUDER#, PCH_INVRMEN and 32.768KHZ clock abnormalities.

　　If the voltage of the CMOS battery is not very low, you can turn to signals such as VCCSUS3_3, RSMRST, PWRBTN, etc. to check. And the LL7 board is the first type of failure. The CMOS battery has no voltage. The very conspicuous J1 and J2 next to the south bridge are right in front of you. Even a novice knows that this must be the RTC_RST#, SRTC_RST# test point.

    I picked up the meter and tested that J2.9V was normal. When I tested J2, there was no voltage. I thought it was C715 that was short-circuited. Isn't this the legendary flash sale? I picked up the tweezers and pried off the C715. 

    When I powered it on again, the current jumped to about 0.5 and it immediately fell off. Why did this happen? Could it be that the CPU is not working properly? Reinstalled again and the sound of waves is still there. At this time, the measured PL17 1.5VSUS_P is normal, +0.75V_DDR_VTT is normal, PL16 +1.05V_VTT_P is normal, PQ79 +1.8V is normal, PL10+VGACORE is normal, and PL13 PL14 VCORE CPU core voltage is abnormal.

    When encountering this kind of problem, I usually don't rush to repair the CPU first, and then measure the conversion voltage, such as +1.5VSUS to 1.5V VDDQ, +3VPCU to 3VSUS, 5VPCU to 5VSUS, etc. At this time, PQ49 was detected, +3VPCU was converted to 3V, 5VPC was converted to 5V, and +1.5VSUS was converted to 1.5V. An abnormality was found. I was ecstatic. Haven't we encountered this problem a lot? You can continue to kill instantly!

　　I believe that veterans all know that this is a common problem with Quanta machines. If a certain transistor field tube is not broken, the +15V is abnormal, or it is not turned on, etc. Then check the drawing, 3V5V is controlled by MAINON, and MAINON also controls PL16 1.05V_VTT_P. The 1.05V_VTT_P measured just now is normal. MAINON must have sent it out, unless there is a disconnection or some possibility.

　　I used an old meter to measure the high level of PQ33 G and 3.3V, which is normal. The low level of PQ37 G and MAINON_G 0V is normal. The upper end of PR93 is normal at 13V, but the lower end is abnormal at around 0.0V.

If the problem like this is not that the PR93 resistor or PC79 capacitor is bad, then there is a problem with PQ49, PQ51 and Q11, because it has not gone anywhere else. Pick up the air gun and dismantle them one by one. If the voltage on the G pole is found, it means it is broken.

　　I just dismantled the first PQ49, measured the G voltage again, and quickly replaced it. After cooling, it was powered on again. After several current jumps, it was able to shut down normally. After plugging in the screen, the long-lost LOGO appeared in front of me.