Dell15-3520 (LA-L947P) No CPU Power Repair

Laptop Model: Dell15-3520 

Board Number: LA-L947P 

Repair Process:

1.     When the laptop turned on, and each voltage is measured. There is no CPU power supply. Check the drawing that PUZ101 power supply is normal, and the open pin 51pin is low level.

1.     Check the IMVP_VR_ON_EN signal to the fourth pin of UC8, and measure the high level of pin 1 and the low level of pin 2.

1.     Check pin 2. IMVP_VR_EN is sent from the C2 pin of EC. It seems that the timing needs to be checked.

1.     The condition for IMVP_VR_ON_P to be turned on is that ALL_SYS_PWRGD is high level and the measured low level is.

ALL_SYS_PWRGD is sent by 1.2V_VTT_PWRGD. The measured 1.2V_VTT_PWRGD is low level.

1.     1.2V_VTT_PWRGD is sent out by the 10^TH  pin of the memory power supply chip PUM01. The 1.2V memory power supply and VTT Voltage must be normal. The measured 1.2VP voltage is normal and the VTT voltage is 0V. The start signal pins 8 and 7 are all at high level and pin 20 is not short-circuited to ground.

1.     After replacing the memory power supply chip RT8207 , the computer started up smoothly.

Happy Repairing!!

Dell 3579(LA-F611P) On & Off Problem Repair

Laptop Model : Dell 3579

Board Number : LA-F611P

Fault : On & Off Problem

Repair Process :

After disassembling the Laptop and plugging in the adapter, it was able to power on. After a while, it automatically powered off and shut down.

 When pressing the switch again, there was no response.The test trigger switch is 0.4v, which is abnormal. power_sw#_MB, chase +RTC_CELL, this voltage is used as a pull-up, test the RE41 resistor 100k, it is normal.

One end is 3.3v, the other end is 0.4v, it is connected to CE33. The other one is POWER_TB_DOCK#, first remove the capacitor, the voltage It's back to normal, and the machine can be switched on and off normally.

Happy Repairing !!

 

 

ASUS PRIME H310M-F R2.0 Does Not Power On

Please Find The Motherboard Image (With Board Number) Below:-

There is no +5VSB , and it is found that the G electrode voltage of PQ4002 (P-channel MOSFET) is more than 2V and does not conduct.

 

A 4120 ohm resistor   is used as the 5VSB_ATX pull-up resistor. I changed It to 85C and 75K and it still doesn't work.

Finally, I replaced it with PQ4002 . Working Fine 

Happy Repairing !!

Dell 2420(10315-1) Not Charging. Even After Changing The Battery Repair

Laptop Model: Dell 2420  

Board number: 10315-1

Fault: Not Charging. Even After Changing The Battery.

 

Measured Fault:

 

The battery installed in the machine of the same model cannot be recognized (battery is bad), the single power supply motherboard can be turned on normally, and a good battery of the same model is installed at the same time when the power is plugged in.

Sometimes it can be turned on and charged and sometimes it is protected (the motherboard is bad).

 

Repair Process:

Plug in the protection at the same time, first check the protection isolation module: the three isolation tubes are all good, the charging chip meets all conditions and has output level AC_IN#, indicating that the chip is OK, but the charging chip was replaced with 24737 The fault remains.

It was found that the single-battery mode could not be turned on, and the test again found that there was no standby. The linear test again successfully output no PWM start signal.

The final turn-on signal S5_ENABLE was sent by EC. The test again showed no EC standby voltage. The EC standby came from the linear conversion and was finally controlled by Q2703.

At KBC_ON#. KBC_ON# is controlled by any one of the switching signals KBC_PWRBTN# and AC_IN#, as illustrated below.

This is an energy-saving circuit. When the adapter is inserted into this circuit, it is controlled by AC_IN# to generate EC standby.

EC works normally and the output standby is turned on. When a single battery is inserted, press the switch to generate standby, and this signal is continuously pulled low by EC.

After studying the triggering of the above circuit, EC standby came out, and PWM turned on, but there was still no output. I checked the waveform and found that both 3 and 5V were active, but none of the outputs were normal.

Then I plugged in the adapter and found that the motherboard It is in the protection state. This kind of weird fault can be easily replaced with a 51125, and the battery mode can be successfully turned on.

It shows that the motherboard protection is caused by the abnormal output of the standby chip, but it is not abnormal every time. The battery mode is more frequent, so the battery circuit is used to repair the machine. The light-up diagram is attached.

Happy Repairing !!

Lenovo Ideapad 310S-14IKB (LA-E221P) Blue Screen Repair

Laptop Model: Lenovo Ideapad 310S-14IKB 

Motherboard Number: LA-E221P

Fault : Blue Screen

 

Repair Process:

 

Replacing the hard drive, installing various systems, and flashing the BIOS were all useless. I thought it was a CPU problem, but I didn’t want to fix it. After all, the computer turned on.

Suddenly I thought it might be caused by poor CPU filtering. There was a big problem next to the CPU. I added an additional capacitor on top of the capacitor and found that it was fine.

There was no blue screen when I entered the system, and it was fine even after a day of testing.

The next day I installed the back cover and found that it could not be installed, so I was forced to find which filter was defective.

When I was searching, I found that 3 of the 4 capacitors I added were useless, and 3 were added to the common point capacitor. This also saves a lot of things.

It is powered by the graphics card. If you remove the added capacitor, it will indeed cause a blue screen. Adding the capacitor will not cause it.

Comparison before and after adding capacitor.

After installing and testing for two days, there was no problem.

Happy Repairing!!

Dell 5547 (LA-B012P ) Screen Brightness Cannot Be Adjusted Repair

Laptop Model : Dell 5547

Motherboard Number: LA-B012P ZAVC0 R1.0

Fault: Only The Lowest Brightness Can Be Used. When The Brightness Is Increased, The Lamp Flickers And Becomes Darker.

 

Repair Process:

 

I got the laptop for a test run and found that the brightness could not be increased regardless of using keyboard shortcuts or the control panel, and the problem persisted when changing the screen.

 After disassembling the machine and flashing the BIOS, the problem is still the same. It seems to be a circuit problem. I found a drawing from the forum and first measured the screen interface voltage.

When I measured the signal of pins 39 and 40 + INV_PWR_SRC, I found that it was only 5V. Normally it should be 19V, which is low.

Continuing to trace this signal, we found that it came from the LCD backlight control circuit.

The EN_INVPWR signal is turned on QX1 to form a voltage dividing circuit, and the measured EN_INVPWR voltage is normal. 

From the figure, we know that the common point B+ 19v is sent to the QX2 S level, and at the same time, it is divided by two resistors and sent to the QX2 G level. If all voltages are normal, SD turns on and outputs 19V +INV_PWR_SRC. 

The measured G-level voltage is abnormal. The voltage dividing resistor RX2 is normal at 100K, but the infinity of RX3 is abnormal. After the replacement, the measurement turned out to be infinite again.

The measuring capacitor CX4 was short-circuited, and it remained the same even after the replacement. Replaced the small six-pin QX2, measured the resistance of the resistor and found it was normal.

After installing it, the system test was normal and the machine was repaired.

Happy Repairing !!

HP Pavilion G4 (DA0R33MB6E0) Does Not Turn On Minor Repair

Laptop Model: HP Pavilion G4

Board Number : DA0R33MB6E0　

Fault: Does Not Turn On

 

Repair Process:

 

After disassembling the machine sent by a colleague and measuring the major inductors and common points, no short circuit was found. It dropped to 0.001 after being plugged in and on standby.

The measurement did not show 3.3V or 5V in standby, and it was found that the standby chip had been replaced.

Open the drawing and measure the data related to the standby chip: VIN: 19V (normal); VREG3: 3.3V (normal); VREG5: 4.9V (normal); so I concluded that the standby chip is not broken.

The capacitors next to the switch are prone to problems. After observing, I found that these capacitors were corroded by water.

I thought it would be better to remove them, so I removed them. After dismantling it, it was found that the fault persisted and it still did not trigger. Continue to measure the switch interface voltage.

+3VPCU: 3.3V is normal, NBSWON1#: 0V is abnormal.

The connection between NBSWON1# and EC and +3VPCU is abnormal. After measuring R442, we found that both ends of R442 are 3.3V (normal), so we connected R442 to the 4th pin of the switch (NBSWON1#).

After connecting, the current is triggered and runs all the way, and the Laptop is successfully turned on.

After entering the system, everything is normal and the Repair is completed. 

Happy Repairing !!

DELL 14-7447 (DA0AM7MB8D0)Laptop Not Charging & Adaptor Error Repair

Laptop Model: DELL14-7447

Board Number: DA0AM7MB8D0

Fault : Not charging

 

Repair Process:

 

The system showed that the battery power was 75%, but the adapter was connected. Everyone knows about choosing an adapter when charging DELL laptops, so the customer bought several original adapters, but none of them worked. It seems that the adapter has been excluded.

　　The battery can also be recognized. It is also possible to start the computer with the battery alone, and it still has 75% power, so the battery is excluded.

When restarting the computer, it says that the adapter is not the original one, and the wattage of the adapter cannot be recognized in the BIOS interface.

Since it is not charging, you must first measure the common point voltage, battery voltage, charging chip conditions, and open the drawing.

As shown in the picture, the common voltage is normal, the battery voltage is 11V, and the charging chip is BQ24737. All conditions are normal. The EC can also identify the battery information through the bus, so it stands to reason that it can be charged.

The charging inductor is not plugged in and the battery is 2.4V. The battery is 11V. Many people think that 11V is not already charged?

But don’t forget that the battery is good and has electricity inside it. Is the electricity in the charging inductor coming from the battery itself or output from the charging circuit? You can actually measure it with an oscilloscope.

As you can see, the voltage at the front end of the inductor is a straight line, not a PWM waveform. Therefore, the 11V of the inductor is the battery's own and not output by the charging circuit. Therefore, the charging circuit is still faulty.

At this time, I am thinking about it. I plugged in the original adapter but it still says non-original adapter. Is there something wrong with the adapter detection circuit? Let’s measure it now.

You can see from the picture that PR14 has been corroded, and the corrosion is quite serious. I used a soldering iron to remove the resistor, and the pad below was corroded and almost fell off.

After repairing the points, I removed a 10K resistor from another motherboard and installed it, which solved the problem perfectly. Then I measured the charge. The front end of the inductor has a perfect waveform.

The power of the adapter was also recognized in the BIOS, and it was prompted to charge after entering the system.

Happy Reparing !!