Lenovo g50-80 notebook water damage no booting repair

Lenovo g50-80 notebook water damage no booting repair

Machine model: g50-80 nm-a361

Cause of failure: notebook water damage

Maintenance process:

Dismantle the machine to process water damage corroded by moisture circuit.

Lenovo g50-80 notebook water damage no booting repair Figure 1.

It is found that the standby current is on the high side. The 3V standby Inductor is a little bit high temperature. One part of the board water damage has two small Capacitor high temperature. Replace it.After power on, it is found that the automatic switch can press Switch again to repeat the same current change process:current change process_When 0 – 0.41-0.13a stops, press auto power off of Switch to measure each Inductor VCC, 19v of common point is normal, 35V standby Inductor is normal,Memory 1.35v is normal, CPU VCC is normal, bridge standby 3.3V is normal, video card 1V VCC is normal.

Then, I first swipe a BIOS, but when I was about to power off and remove the BIOS, I found that the current of auto power off to 0.13a did not move the VCC part of the graphics card high temperature, and the measurement found that the display card VCC was still in the output state, so the graphics card VCC Inductor had 1V VCC, and other memory CPU VCC did not have, and then temporarily did not consider brushing BIOS.

Lenovo g50-80 notebook water damage no booting repair Figure2.

Graphics card VCC high temperature, first exclude the next level large current, because the power is not Current protection, it is not large current.Then the ground Measuring diode value is found to be hundreds of times, so it should not be caused by the graphics card Short circuit. It is considered that the PWM of the graphics card VCC is not under control, and whether the origin of the PWM chip EN of the graphics card VCC is in an uncontrolled high level.

Lenovo g50-80 notebook water damage no booting repair Figure3.
The chip model is isl62771. Because water damage and switch are normal, it is not considered that susp ා has not been sent out. Directly check the original circuit related to susp ා, and find Q6.

Lenovo g50-80 notebook water damage no booting repair Figure4.

MOSFET 2n7002k, composite n-tube, with two n-tube structure inside, and then see the resistance r157 connected with its 6 pin. Because one end of water damage has been desoldered by corrode, replace the resistance, and power on, it is found that the wave noise is still the same. Then, check that MOSFET 2 pin has VCC current of change, but failed to pull down 6 pin VCC to 0V, indicating that MOSFET should be broken, replace Q6.

Lenovo g50-80 notebook water damage no booting repair Figure 5.

Power on found that switch is not automatic, which means that a series of problems are caused because susp ා is affected. Press Switch to trot the current all the way to 0.41a auto power off. Since it is determined that the main VCC is normal, check the secondary conversion VCC.According to the power on sequence, the following conditions should be checked first: 1.05vs, 5vs, 3vs, 0.675vs, 1.5vs.

05 vs normal.

Lenovo g50-80 notebook water damage no booting repair Figure6.

3 vs normal.

Lenovo g50-80 notebook water damage no booting repair Figure 7.

5 vs normal.

Lenovo g50-80 notebook water damage no booting repair Figure8.

Both 0.675vs and 1.5vs are normal, the primary VCC is normal, and the secondary conversion VCC is also normal. First brush a BIOS.After brushing three more BIOS, I gave up, because of the same phenomenon, turn the timing out and check it honestly!Since switch can be powered on, you can skip the previous hangpe Lang Bang ~, from PCH_Pwrok began to check the normal VCC, indicating that EC sent.

Lenovo g50-80 notebook water damage no booting repair Figure9.

Then check sys_Pwrok and VCC were normal.

Lenovo g50-80 notebook water damage no booting repair Figure10.

Then to DRAM_Pwrgd, cpupwrgd, to CPU_Pltrst is normal.What should be touched and what should not be touched has been touched, but no problem has been found.Because water damage also goes to the memory part, not to say the memory Short circuit, read the memory on Current protection, remove the memory, or the same.

auto power off it seems that if the memory is not inserted to 0.41a, is the CPU not sending reset to the memory?Continue to check the memory slot jddr 30 pin CPU_DRAMRST #.

Lenovo g50-80 notebook water damage no booting repair Figure11.

Then the VCC didn’t move back.

Lenovo g50-80 notebook water damage no booting repair Figure12.

It was found that Capacitor resistor was a little blackened. After replacement, it was found that it was still not pulled up by 1.35v, which proved that the single U was not sent out.

Lenovo g50-80 notebook water damage no booting repair Figure13.

After repeatedly checking the timing sequence for more than five rounds, it is found that the memory is missing, reset and start drying (before drying the U, remember to confirm whether the SMB is normal, whether the memory is read and returned to the CPU, that is, whether the memory conditions are met, whether the two pwroks and 25m Crystal are normal, and whether the BIOS is correct).After the completion of the installation test, directly into the system, perfect repair.

Lenovo g50-80 notebook water damage no booting repair Figure14.