How to repair a dead motherboard step by step?


        How to repair a dead motherboard?
laptop motherboard repair, laptop motherboard fault finder
There are two types of problems that a motherboard generally has. The motherboard either goes dead or there is no display on the screen even after the power supply is present. Whatever may be the problem is, but there can be different reasons behind it.  Some of the commonly occurred problems which we frequently face are:

1. Dry solder 
2. Shorting problem 
3. BIOS problem
4. Loose connection
5. Memory and processor problem
6. HDD problem
7. SMPS problem and many others

According to my experience, 60% of the problems occur due to dry solders, loose connection, carbon and moisture formed in the motherboard. 35% of the problems occur because of shorting and the rest 5% due to internal damage. But, I can’t guarantee the steps that I am going to list out here apply to every type of motherboard problem. This actually depends on the condition of the motherboard. As there can be many reasons for a single problem, like loose cable connection, burnt condition, shorting trouble, carbon and moisture formation, memory problem or IC/Chipset getting dry. A motherboard can also become dead, because of the shorting, leakage or an opening in any of the components. This can also lead to a blank or no display problem. 
If you are unable to troubleshoot these kinds of problems through hardware or card level, then it becomes really important for you to adopt IC/Chip-level approach of resolving those problems. Working on-chip level requires thorough expertise of step by step booting sequence and supply sequence. At the same time, it also requires knowledge of a schematic diagram. Without having an in-depth understanding of the schematic diagram, you can’t become a chip level engineer. The schematic diagram consists of every single detail of the IC, its connectivity, interconnectivity, and structure. The major advantage of having the knowledge of sequence or schematic diagram is not only that you can troubleshoot the laptop and desktop problems, but also you can easily troubleshoot the problems of any electronic device.

schematic, schematic diagram

Some useful steps for repairing the dead motherboard: 
Step 1- Mechanical off: The supply which is generated at the beginning on the board is called mechanical off. In this condition, only the CMOS cell (Coin Cell) is connected, while battery and SMPS are not connected. The supply of the CMOS cell goes to ICH/PCH and I/O controller. RTC (Real Time Clock) crystal also gets the supply from a CMOS cell. In this condition, try changing the CMOS cell and observe. If the CMOS cell is ok, then the problem might exist in the component on its path like a resistor.  

Step 2- Standby mode (ALW/PCU): SMPS is the one which is called S5 or Standby mode. Once you plug in the SMPS plug, two types of supply are generated. One with the intensity of 5 volt and second with the intensity of 3.3 volts. The board of a laptop has separate regulator circuits for both the supplies; on the other hand, the desktop board does not have this kind of circuit. The standby voltage of 5 volts is generated on pin number 9 of the SMPS and this 5 volt gets converted into 3.3 volts through the regulator. And this 3.3 volt supply directly goes to ICH/PCH and through I/O controller it reaches the positive pin of a power switch. If the positive pin of the power switch is not getting supply, then check thoroughly the components from pin number 9 of SMPS to I/O controller and from I/O controller to the positive leg of a power switch. If you find that all the components are ok, then change the I/O controller. Many times, it also happens that the machine is turned on from SMPS, but the display still is blank. In such scenarios, try to change the SMPS.

Step 3- Power ON mode: In this situation, pressing the power button turns on the motherboard, but even after pressing a button the system is not getting switched on. The supply is also getting generated on the positive leg of the power switch, then in this situation go ahead and try changing the SMPs. If the SMPS is ok, then there might be a problem that exists in the RTC crystal. Try either shorting or changing the RTC crystal, because shorting in RTC crystal is also one of the reasons behind the dead motherboard. If you are unable to fix the date and time, then also try to change the RTC crystal. As RTC crystal is actually responsible for fixing the system and date/time settings. If you are unable to switch on the system even after performing the above steps, then change the RAM. Check whether the processing is getting heated or not, if you find it ok, then check RST (3.3V) and clock (1.6/1.7V). If these supplies are up and running, then it means Hard-to-start complete.
Step 4- Hard-to-start: In this situation, the sufficient intensity of voltage is generated at the specified location of the motherboard; it simply means that supply, RST, and CLK are getting generated properly. If the RAM, CPU and ICH/PCH are ok, it directs you to hard start ok. Soft start (Logic) starts functioning only after the hard start process is completed. 

Step 5- Soft-start:  Soft-start is getting loaded in the system BIOS (logic) and POST.
If all the components of the motherboard are receiving power but still it is not working, it means the components have not received the logic in a sequential manner. Unless the components receive the logic which is required for the components to operate smoothly, the motherboard will not function properly. The components of a motherboard actually gain the required power from BIOS and the once the components receive the power the PLT reset signal is transmitted by PCH/ICH. Post PLT reset activity; the processor receives the instructions from BIOS and then ultimately all the data for initialization are issued by the BIOS. This process is what is called a soft start.
After reset, BIOS will read the device and the first instruction runs POST
Post BIOS test completion, it switches to MBR of the hard disk

If your operating system is:
                                           GUI= Windows will open
                                           CUI= CMD will open






Comments

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    Replies
    1. Above information is very helpful, thanks for sharing it.

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  2. Good Information, keep it up

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