DELL 3421 Does Not Power On

 

Laptop Model: DELL 3421

 

Board Number: 12204-1

 

Fault: The Notebook Does Not Trigger, Does Not Power On, And Is In Standby Mode At 0.01

　

Maintenance process:

 

There is no short circuit in the whole board. Only the resistance of the CPU and the graphics card to ground is relatively low (the resistance of the third-generation onboard CPU to ground is generally 3-5 ohms), the voltage is 3V5V, the EC power supply is reset normally, and AC_IN# is 0V ( EC 73 feet are normal).

    LID3.3 is normal, but the voltages of RSMRST# and PWRBTN are constantly jumping, and the power supply indicator light in the lower left corner is also flashing.

Find RSMRST# and PWRBTN next to the EC and cut them off directly.

    The voltage on the EC side kept jumping from 0V to 3V when measured. Replace the EC directly. After replacement, the fault remained the same. I reviewed the EC working conditions again and found that except for the two voltages RSMRST# and PWRBTN that kept jumping, everything else was normal.

　　

    I had to go to the oscilloscope to check whether each voltage output was stable. The common terminal, 3V5V, and the 3V5V linear voltage. The oscilloscope directly adjusted the automatic gear and caught 19V. The linear 3V5V was normal, but when it caught 3V5V, it was repeated and the voltage would drop instantly. Go up again.

    Then grab PWR_3D3V_EN2 and PWR_5V_EN1, the voltage will be pulled down and up again repeatedly.

    It is traced that the source of PWR_3D3V_EN2 and PWR_5V_EN1 is EC and connected to the PURE_HW_SHUTDOWN# signal. PURE_HW_SHUTDOWN# controls ECECRST#.

　　

    When grabbing PURE_HW_SHUTDOWN# and ECECRST#, the voltage will be pulled down and up again repeatedly. It is normal to directly remove Q2701 and grab ECRST#.

　

　But PURE_HW_SHUTDOWN# will still be pulled down repeatedly, because PURE_HW_SHUTDOWN# went to several places, and after looking for it for a long time, I only found D3601.

    I couldn't find anything else, so I took off the D3601 directly. After taking off the D3601, the board triggered the display normally. I installed it directly and tested it repeatedly for half a day, but it was normal. I was too lazy to trace the source of the PURE_HW_SHUTDOWN# signal.

Summarize:

　　The fault point is that PURE_HW_SHUTDOWN# is unstable, causing ECRST to reset continuously, causing the computer to not boot.

Happy Repairing !! 

Acer Aspire VS-471 Occasionally The Laptop Can Be Turned On Repair

 

Machine model: Aspire VS-471 Series

 

Version number: 11309-2

 

Fault phenomenon: Occasionally The Laptop Can Be Turned On

 

Maintenance process:

 

The machine I received is a second-hand mobile phone. The bridge has been replaced, but the BIOS and EC have not been touched. I am also a little confused as to why I don’t just turn on the machine and directly touch the bridge. I don’t know what the fault was in the first place.

The bare-board plug-in standby mode is a bit large, and the screen can be displayed even when you turn it on by pressing the switch, but it won't turn on when you turn it off and on again. After a while, the bare board can be plugged in and it can be turned on again. The bridge is a little hot when you touch it, and the temperature feels abnormal.

　　There is no 3V and 5V voltage when it is not turned on. After pressing the switch, it can be measured that 3V and 5V come out and then fall off again. The oscilloscope does not find any problems when playing the waveform. RSMRST# also comes out and falls off. The standby chip is also jumping when it is turned on.

　　

Because it can be turned on occasionally, I turned the standby chip low to allow 3V and 5V to be generated directly. But it still didn't work when I turned it on again. I tested that pin 117 of U2701 is always 0V.

       

         This is definitely not normal. After flashing the BIOS, it is still the same. The power supply and reset are normal. I directly replaced the EC, but the result is still the same problem. After looking around the forum, some experts said that the temperature control U2801 may cause this problem. Even if I just dismantle it, the problem is still the same.

　　Check to see if there is a problem with the bridge that pulls down pin 117 of the EC, resulting in no jump. Check the RTC condition, check the DSW voltage, and the BATLOW is normal. If you directly replace the bridge, the result is still the same.

　　I still have confidence in the BGA, but I have no direction. I started to doubt the standby chip, and it still didn't work after changing it. But this time after changing it, I can no longer turn it on occasionally. Now the problem seems to have become bigger. I started testing the EC conditions from scratch, and it felt wrong when I tested ACIN.

        It was normal when I first picked up the machine for inspection, but now it is not normal. I directly tested the isolation tube and found that PU4001 was not fully connected. 

        This discovery made me feel baffled. How could a machine that can be turned on occasionally not be fully protected and isolated? Continuity, I really don’t know if this is an original fault, let’s deal with it first! There was something wrong with the 20-pin resistor and capacitor of PU4003, so I replaced them directly.

After powering on the machine, it also became smaller in standby mode. After troubleshooting and repairing, I still didn't understand what the original fault was in this machine and what the bad things were. 

Only by looking at the expert can we determine the cause of the problem. I think the protective isolation is not completely conductive and should not cause this phenomenon.

Happy Repairing !!

Acer E1-451 Notebook Does Not Recognize The Battery

 

Laptop model: Acer E1-451

 

Board number: 12276-1

 

Fault: The Notebook Does Not Recognize The Battery

 

Maintenance process:

 

After replacing the battery, there is still a red cross. The BAT_SDA BAT_SCL resistance is normal after disassembly and the battery is inserted. BAT_IN# is 2.1V when the battery is inserted. BAT_IN# is active at low level and should not be high when the battery is inserted.

The trace source is pulled up through R2775 and goes directly to EC. EC comes with a program, and without 809H, there is no way to refresh the EC program, so you can only be a dead horse. I remember seeing a post about another model before that just replaced the resistor of the battery interface.

 

I couldn't find the 330 resistor on the laptop's scrap board, but the Asus platform is more powerful. I removed it from the platform and replaced it, but the problem was still the same. BAT_IN# was also connected to a Zener diode PD3902, so I replaced it directly, but it didn't work. This problem has not been fixed before.

Suddenly I thought about whether it was a problem with the pull-up resistor. I measured that R2775 had 100K, which was normal. I found a 100K resistor and replaced it, but it still didn't work. But when I measured BAI_IN# again and plugged in the battery, it showed 3.3V instead of 2.1V. Try changing the resistor to a larger one.

 

　　Find a 200K resistor and replace it. Plug in the battery and measure BAT_IN#. It is low. You can turn it on by pressing the switch. Then you replace the customer's previous battery but it still can't be turned on. Then you replace it with a new battery and it still can't be turned on. 

    Measure BAT_IN# again. It's back to high level again. I have to listen to the captain's lecture in the evening and try changing a 200K resistor. It works fine with new batteries.

    This time I didn’t dare to use the old battery to turn on the phone. The old battery was probably broken. I tested the new battery for a day and found no problem. Charging and discharging were normal.

Happy Repairing !!

Lenovo 15ISK NM-A711 Notebook Does Not Turn On Repair

 

Laptop Model : Lenovo 15ISK NM-A711

 

Fault: The notebook does not power on, and there is no response when pressing the power button.

 

Maintenance process:

 

When disassembling the machine, it was detected that there was a 3.3V short circuit of 2 ohms. When the power was turned on, the temperature could not be detected, and the 3.3V voltage burned 2A. When looking with a thermal imager, only redness near the PL600 was seen.

 

I thought the south bridge was short-circuited, but I measured that the capacitors below the south bridge were not short-circuited, and the capacitors above the bridge were not short-circuited. 

    I thought the south bridge was burned. If the other bridges were burned, they would be obviously hot.

　　The vinyl bridge is hard to replace and the bridge is very expensive. I was ready to give up, but it still felt weird. I used thermal imaging again to put my finger on the South Bridge crystal and clearly saw that the finger part was not red. 

    Could it be that the bridge was broken? Even if the 3.3V inductor is removed, the burn is still not obvious, and the 3.3V power supply chip is also the same. The thermal imaging is just this one, and you can't tell which one it is

    Fumigated it with rosin and then burned it. Sure enough, there was a melted part. After a closer look, it turned out that the 3.3V output filter capacitor was short-circuited. The key is that this kind of capacitor is generally used for 20V filter capacitors and rarely breaks, so I didn’t use it. 

    After thinking about it above, I removed it and tested it, and it turned out that it was short-circuited. The 3.3V short-circuit was eliminated, and it could be turned on after powering on again.

 

Happy Repairing !

Acer ES1-411 Laptop Not Powered On Repair

 

Laptop Model: Acer ES1-411

Fault: The notebook does not power on

 

Maintenance Process:

 

Connect the adjustable power supply and the standby current is 0.001. After pressing the switch, the current is 0.059. It seems that there is no power, so the motherboard is removed.

    There are 3.3V and 1.8V measured in standby (for CPU standby), but there is no 5V. Turn off the power supply and set the 5V resistance to 0. After looking at the circuit diagram, 5V goes to several power chips. I tried the burn-in method but couldn't burn it out, so I removed the filter capacitor at the 5V inductor end.

    After removing the capacitor, the resistance returned to normal. When pressing the 5V switch, only 1.4V came out. The chip is probably broken. I put it on the next day after buying it, and the 5V came out perfectly.

    The current also jumped several times and then the machine turned on smoothly, and the repair was completed.

Dell 14-5420 Not Turn On After Connecting The Hard Disk Repair

Laptop Model: Dell 14-5420

Fault: The Laptop Does Not Turn On After Connecting The Hard Disk.

Maintenance process:

     

    The Laptop will not turn on even if the hard drive is inserted. The Laptop will turn on even if the hard drive is not inserted. Is the hard drive broken? Replaced the hard drive and still the same. Tested the power supply of the hard disk interface and found that the +5V_RUN voltage was abnormal and only 2.6VA

After checking the source, I found that the power supply of the hard disk is converted from the standby 5V, which is the secondary voltage. To pass the standby 5V, PQ16 must be turned on, and PQ16 is controlled by PQ19.

In the standby state, pin 2 RUN_ON of PQ19 is low level, and then the above 5V conduction pulls it low to cut off PQ16. When we press the power button, RUN_ON emits a 3.3V high level conduction, causing PQ19A to cut off. The above +15V_ALW high level turns on PQ16 to achieve secondary voltage conversion.

 

When I measured PQ16, I found that the G level was only 5V. This must be abnormal. First of all, I ruled out whether there was something wrong with the PR54 resistor. The measured resistance value was normal.

 

When I measured pin 5 of PQ19A again, it was 0V, which was normal. At this time, the PC44 was still the same after being directly removed. Is there something wrong with the voltage of +15V_ALW? But I don't think it 's possible because the voltage is abnormal.

 

It was impossible to turn on the Laptop with or without the hard drive installed, and the current would not flow, that is, there was no secondary voltage. I mainly suspected that PQ16 had lowered the voltage, so I removed it directly. I found that the G-level voltage returned to 15V. After replacing PQ16 with a hard drive, the power came on. I found that the fan was not spinning. I tested the 5V power supply of the fan and found that it was not powered. I directly shorted pins 2 and 3 of U52 and it was perfectly repaired.

Happy Repairing !!

Gigabyte GA-H61M-DS2 REV 3.0 The Motherboard Does Not Power On Repair

 

Motherboard Model: GA-H61M-DS2 REV 3.0

Fault: The motherboard does not power on.

Repair process:

　　A Gigabyte GA-H61M-DS2 motherboard, the initial failure of the motherboard does not power on.

    The motherboard's appearance showed no obvious signs of damage or burns. Plug in the power supply and test without triggering. Go straight to the switch pin and measure 1.2V. Observe that a 6-pin tube is found near the switch pin. Turn off the power and measure that this tube is connected to the switch pin. After removing it, measure 3.3V.

    Triggered at boot, the motherboard keeps restarting without running code.
　　

    After measuring each power supply, the memory power supply is normal, the bridge power supply is normal, the CPU VTT is normal, and the CPU power supply is not. Check the drawings to search for the DU1 CPU power supply chip, ISL95836.

Check pin 25 and 26 VDD VCCP, 5V is normal;
check pin 9 VR_ON - VTT-PWRGD is normal;
check pin 5, 6, 7 and 8 1.05V is normal (VTT pull-up);
check pin 10 NTC temperature detection is normal.
　　

Directly replace the power supply chip, and then turn on the CPU to power the CPU, but the code still does not run after restarting.

Search PLTRST in the drawing and find the platform reset renamed -PFMRST. Go to the IO68 pin and make IO 65 and 64 pins send out PRST1-, PRST2- and rename it -PFMRST1, -PFMRS2 through the resistor. All three measurements are normal.

    Find the CPU reset CPUURST, which is controlled by -PFMRST1 to turn on Q28 and pull down the second pin of Q29 to cut off Q29. VCC3 divides the voltage through R222 and R223 to get a voltage of about 1.1V and renames it -CPURST .The measurement is normal.

Since everything is normal, I refreshed the BIOS and the fault persisted.

　　Check the IO voltage. Pin 1 is normal, pins 126 and 127 are 2.0 normal, pin 128 is 2.8V. Pin 128 is divided by VCC3, but the two voltage dividing resistors on the motherboard are not there. Turn on pin 128 and measure it. It is found that 2.8V is divided by VCC3. IO is issued, which is normal for the time being.

Check the PLL voltage to be 1.8V, which is normal.

VRMPWRGD, normal.

I found the notes and opened the timing and learned that after the CPU is reset, it goes to the bridge through the DMI bus, and the bridge reads the BIOS through the SPI bus.

 

Welded the BGA, plugged it in and turned it on. The code started to run and the display came on, but it didn't trigger when I turned it off and on again. Oscilloscope measures crystal oscillator, no waveform. I replaced the crystal oscillator directly and everything turned on normally

Happy Repairing !