Acer 4752G (10267-4) Laptop Not Charging Repair

 Laptop Model: Acer 4752G

 

Board Number: 10267-4

 

Fault: It can be turned on and used normally with the power supply or battery, but the battery is not recognized and cannot be charged, the charging light does not light up, and the battery is not detected when entering the system.

Maintenance Process:

 Open the drawing, find the battery identification signal BAT_IN#, plug in the battery and measure 2.4V, which is obviously wrong and normal is 0V.

Then find the problem, BAT_IN# is connected to 4 places, pull-up resistor, EC, resistor, and Zener diode. First, I measured the resistance of PRN3901 to be 33 ohms. I found the pull-up resistor and measured it online to be 3.3K. I thought the resistance had become smaller and replaced it with a new 100K resistor, but the result was still the same.

 

　　Then directly remove the pull-up resistor and then measure BAT_IN#, and there is still a voltage of 2.4V. If you think about it carefully, it may be a problem with the exclusion resistor. The BAT_SCL and BAT_SDA connected to the exclusion resistor have 3.3V. After removing the exclusion resistor, the voltage is gone.

Install three 33 ohm resistors and measure the voltage on BAT_IN#, which is normal.

Then I installed the 100K pull-up resistor, but BAT_IN# has voltage again, which is very strange! The voltage comes from the pull-up resistor.

 

Change the pull-up resistor to 300K and BAT_IN# becomes 0.14V. Then change the resistor to 1M. The result is BAT_IN# is 0.05V. Plug in the battery and it can be charged. Install and test everything. All normal.

Happy Repairing !

DELL 14Z-5423(11289-1) Laptop Not Charging Repair

 Laptop Model: DELL 14Z-5423

 

Board Number: 11289-1

 

Fault:  In Battery Mode Laptop Not Working . AC Adaptor Working Fine

 Maintenance process:

 

Open the drawing, find the battery identification signal BAT_IN#, plug in the battery and measure 2.4V, which is obviously wrong and normal is 0V.

 

I replaced it with new one that showed the battery level and could be used to turn on the laptop but still couldn't charge. I saw that the charging chip used in this one was BQ24727. I happened to have a BQ24737 on hand, so I tried to replace it, but the fault remained the same.

 

　　After restarting the laptop, I find that sometimes it prompts that the power of the adapter is not detected correctly, and sometimes it boots normally. I wonder if the adapter power detection circuit PSID_EC is abnormal.

First analyze the drawing. The PSID_EC circuit is sent to the EC through the interface through PQ3801 and then through PR3807. The normal voltage should be 3.3V. After measuring PQ3801, it was found that the D-level voltage is 2.2V, the G-level voltage is 1.5V, and the S-level voltage is 1.5V.

 

　　Circuit analysis shows that PQ3801 is controlled by an NPN transistor PQ3802. After 3.3V is divided by resistor PR3811 and resistor PR3802, a voltage lower than 0.7V is obtained, causing PQ3802 to cut off, causing 5V_S5 to pull up the G level of PQ3801 through PR3803. PQ3801 is turned on.

 

　　After measurement, the voltage of pin 1 of PQ3802 is 0.3V, but the voltage of pin G of PQ3801 does not reach 5V. Find an NPN transistor to replace it.

After the replacement, the PSID_EC voltage returned to 3.3V. After entering the system, it was found that the battery could be charged normally. There is a detail that needs to be paid attention to when repairing this Laptop.

BATSW1 in the red circle in the picture above, this switch should be turned to the ON position. If it is in the OFF position, some batteries cannot be recognized, and some batteries can be recognized, but they will not be charged.

Happy Repairing !!

Acer E1-572 (LA-B162) Laptop Not Powered On Repair

Laptop Model: Acer LA-B162

Board Number:LA-B162

Fault : The Laptop is not powered on and the standby current cannot be seen.

　　

Maintenance Process:

 

When I turned on the power, there was no response, no power, and I quickly took it apart. The board was new and had not been repaired.

Since there is no power and no standby current, the first thing that comes to mind is that the common point is short-circuited, because many of the current new machines have short-circuited common points, and the ammeter has no response at all, and some have prompts.

As expected, the value of a dozen common points is unexpected, and the machine immediately burns up. Show the original shape (if the filter capacitor of the upper tube is short-circuited, it will be killed directly).

This capacitor is short-circuited. There is only one on the board. After it is removed, the value is restored. When the power is turned on, the ammeter will see the current coming out and then disappear. It seems normal. After connecting the switch and pressing it, it lights up perfectly. However, after the installation, I found that the power is 0.53. Do not move.

 

　　After dismantling the bare board, there was no problem. Could it be caused by peripherals? Optical drive, keyboard, touchpad, or USB tablet? Now that you have an idea, let’s do it! Looking at it one by one, it turned out that after all the downloads were completed, it was still possible to click. Finally, after installing the hard disk, the problem surfaced and it was caused by the hard disk. The same thing happens when trying another hard drive.

 

I checked the hard drive condition myself and found that the 5V power supply fluctuated a bit, but it was not a current that would stop the computer from turning on. 4.9-5.2 fluctuated like this, and the data line values ​​were all normal. I checked them one by one and found no problems. At that time, I felt that the fluctuation of 5V was not enough, so I directly soldered it to convert it, that is, this.

Nowadays, many chips like this control 35V to the rear, and the result has not changed. The same goes for flashing the BIOS. I have been going back and forth like this for a long time.

I have checked everything that needs to be checked. If there is no solution, the target starts to release the bridge itself. The result After installing the BGA, I did not replace it and soldered it, but the result was the same.

I found the drawing and looked at it. Is it possible that it was caused by removing the capacitor on B+? I didn't think much and added another one.

  

The result is really surprising. After removing the added capacitor, it returned to 0.53 of the hard disk. Now I removed the inductor and connected it directly, and the result is that the computer can be turned on.

The hard drive was also normal. I thought it was really caused by the inductor at first, so I replaced it with an inductor, but it turned out that it was not.

 

It was the same thing if I didn't replenish the capacitor after replacing it. The hard drive wouldn't turn on, and now I only have the chip without replacing it. I just replaced it and just replenished it. After returning the capacitor, the computer turned on. I think it was caused by the B+ filter capacitor.

Happy Repairing !!

Acer E1-471G (DAZQSAMB6E0) Laptop No Power

 Laptop Model: Acer E1-471G

 

Board Number: DAZQSAMB6E0

 

Fault : When connected to the power supply, the current is 0.023, but there is no response when pressing the switch. The standby current of this notebook is obviously high.

　　

Maintenance Process:

Remove the motherboard and measure +3VPCU +5VPCU, both of which are only a few points. VREG3 2.1V, VREG5 4.6V, VREG3 voltage is low.

Try to replace VREG3 and filter capacitor PC79.

When the power is connected, the standby current becomes 0.002, which seems to have returned to the normal standby current. The measured VREG3 3.3V is normal. Press the switch to  power on, and the screen is turned on normally. The repair is completed.

Happy Repairing !!

DELL 5750 No Display Repair

 

Machine Model: DELL 5450

Board Number: DAJW8CMB8E1

Fault: No Display

 

Maintenance Process:

 

It is detected that the notebook does not display when it is turned on. It can occasionally display but the screen is still dark. It is judged that the screen cable is broken. After replacing the screen cable, the screen flashes (dark screen - bright screen alternately).

　　The screen flashes when the motherboard screen cable interface is pressed with a finger. When testing the dark screen, the LED-BL 19V is normal and the backlight turn-on signal LCD_PWM_IN 0V. The fault point should be here. When the screen flashes, the LCD_PWM_IN 0-1.7V jumps.

Look for LCD_PWM_IN to the composite diode.

    There is no disconnection in the test, and the LCD PWM EC is 0V both bright and dark.

    When flashing alternately, the EDP_PWM_OUT voltage changes from 0 to 1.7. Find out that EDP_PWM_OUT is sent by pin 12 of PS8620/23. There is no disconnection during the test.

    At this point, it can be basically confirmed that the PS8620/23 or EC or bridge is faulty. Considering that there are traces of the pot being dropped on the machine casing, it is estimated that the bridge is probably more likely. In the end, I decided to be a flyer and find the screen power supply of 3.3V.

    Connect a 10K resistor flying wire in series to pin 3 of the D17 diode. After booting, there will be a PWM start signal, as shown in the picture above:

Happy Repairing !

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.

Gigabyte H81M-DS2 REV2.1 Motherboard Keeps Restarting

Motherboard Model: Gigabyte H81M-DS2 REV2.1

Fault : The Motherboard Keeps Restarting

Repair process:

    A Gigabyte H81M-DS2 REV2.1 motherboard. The fault is that the motherboard keeps restarting after powering on.

    Flashing the BIOS failed. I tested the memory power supply and found that the bus power supply was missing. I checked the drawing and found that it was provided by RT9199. The test power supply, startup, and benchmark were all normal, but pin 4 VOUT had no output.

    After replacing the UP0109P chip, the machine turned on perfectly and repairs were eliminated.

Happy Repairing !!