Common faults and maintenance methods of embedded motherboard

1. Observation method:

Observe the main chip, PCB board, power IC, electronic form.

① Observe whether the main chip has obvious burning, burnt appetite, and burns.

②See if there is a short circuit in each.

2. Touch method: (Power-on alarm):

Touch each chip, IC, etc. of the motherboard to see if it is overheated or overcooled.

Overheating: ①Internal short circuit, ②High power supply voltage.

Too cold: ①open circuit, ②no power supply, ③working conditions are not met.

3. Search method:

ISA: The first 8 D lines have the same R to ground. The first 20 lines A are the same as ground R (some boards are stuttering). The last 7 lines A are the same to the ground R. The last eight D lines are the same as the ground R. Generally, it should not exceed 15Ω between them, and the extrusion of IRQ, DRQ and DACK should not exceed 25Ω.

PCI: Thirty-two AD lines have the same R to ground. It is normal for some motherboards to have one that is tens of Ω smaller than the other 31 to ground. autumn method: Important test points: RESET, SCLK, OSC, BE0-BE7 (signals for data address work) A3 (signs showing bridge work), CS permission, OE. V. Locking wave method: 

Asimple way to judge whether the motherboard chip is good or bad:

1. Measure the resistance value.

2. Test with clock input and no clock input (the chip is broken).

3. The damage of the north bridge chip will bulge a little more.

4. 3.3V short-circuits to ground are mostly BGA faults, I/O chips, clock generators, and power ICs.

5. DBSY (Data Busy Signal): Disassemble the BIOS, plug in the CPU (three conditions are met), there is no wave in the test, and the north bridge is broken.

6. New board failures are mostly: power IC, I/O part, BIOS. Old board failures are mostly: South Bridge (FX, VX), BIOS,

7. I/O.

Examples of detection of digital cards:

07-09 crashes; 08-09 memory has problems; 01, 04 motherboards other than the memory stick are not turned on;

01-11 are all related to the memory; there is a problem with the graphics card; U1—U6 do not read the memory C1 and C6;

05-07 There is a problem with KEYBOARD; 4b is displayed; b9 In addition to bus, there may be a problem with the north bridge and memory.

05-01 There is a problem with the memory (the north bridge part); 53-54  booted, but did not read the memory, and did not boot before;

05-02 Display part short circuit; 

08-25 Check P part of North Bridge;

07 RTC

Sound card repair

  1. Cannot detect: check power supply, main chip, crystal oscillator.

  2. CD has sound, VCD is silent → mostly because the main chip on the sound card is broken.

  3. The CD is silent, but it can be detected 

Graphics card repair

No display (no response at all, on the screen): Check the main IC power supply, if it is wrong, the IC itself is bad, or the BIOS is wrong or bad.

1. Graphics card not graphics card: check power supply, BIOS, crystal oscillator.

2. Huaping: the video memory ② is bad or the BIOS is wrong, the accelerating end video memory is bad, the main chip is bad, and the crystal oscillator is bad.

3. White light: The video memory is bad. 3. Discoloration: The main chip or ①② The video memory or active video memory is broken → you can first unplug the active video memory to check.

4. Color cast: the three colors are wrong → the main chip is broken.

5. Lack of color: The resistance or fuse (inductance) of the output terminal of the main chip is broken. 

Note: The insurance on the motherboard, sound card and graphics card are replaced by inductors L and resistors R. From the North Bridge to the CPU block.

15. Most of the failures of the new board are ① power IC ② I/O chip ③ BIOS. Most of the failures of the old board are ①South Bridge (FX, VX)②BIOS③I/O chip.

16. Cannot display ① power supply ② clock generator ③ I/O chip.

Wisdom industrial machine troubleshooting process

1.The first step: After seeing the host or mainboard, first check the date, then check whether the wiring on the mainboard is connected correctly, and secondly check whether the capacitors on the mainboard are bulging, and the materials are damaged, fallen off, or burned. 

2. The second step: Unplug all other external devices on the motherboard, leaving only the basic power supply line of the motherboard, then unplug the memory and power on, check whether the motherboard has a long beeping alarm, the CPU fan speed, and whether each power indicator is normal and there is a memory alarm If the sound is sound, the CPU is normal. If there is no memory warning sound, the CPU is not working. If there are other sounds other than the memory alarm sound, it is considered to be a CPU or motherboard failure. 

3. The third step: Clear CMOS and then power on to see if the motherboard can alarm 

4. The fourth step: Remove the CPU fan and touch it with your hand to see if the CPU has a temperature. If there is a temperature, it can indicate that the CPU is working. If there is no temperature, it can prove that the CPU is not working properly. In addition, you can remove the north bridge heat sink. Check the parts for hot spots. 

5. The fifth step: If the motherboard is not hot, then try to replace the CPU, memory module or re-plug the motherboard, power supply plug, small motherboard, half-length card and many other CPUs are embedded on it. The general problem lies in the memory. For example, the gold finger oxidation causes a virtual connection, which causes the motherboard to fail to start. Therefore, we need to wipe the golden fingers with an eraser, etc. or re-plug the memory stick several times to see if the motherboard can start normally. Full-length cards are also suitable for this kind of.


1 short: memory refresh failed. Solution, replace the memory stick

2 short: memory ECC validation error. Solution: Enter CMOS settings and turn off ECC validation

3 short: system basic memory (first 64KB) check failed

4 short: system clock error

5 short: CPU error

6 short: keyboard controller error

7 short: system real mode error, can not switch to protection mode

 8 short: video memory error

9 short: ROM BIOS checksum error

1 long and 3 short: memory error

1 long and 8 short: display test errors Second

the main board is not bright analysis and solutions

First:The machine has no response, the power light is off, and the power is not turned on

1. Check whether the power supply line is normal

2. Check whether each thread on the motherboard is well connected, such as 6pin cable, 20pin power supply, etc.

3. Check whether the motherboard has burnt parts

4. If there is a power indicator on the motherboard, check if the indicator is on

5. Trigger the switch to see if the motherboard can start

6. If the indicator on the main board is not on, short the green wire and black wire of the power supply to see if the power supply is Normal, finally replace the power supply to test whether the motherboard is normal

second:The motherboard can be powered on but there is no memory self-checking sound

1. Check whether the CPU power supply line is well plugged in

2. Remove the heat sink of the north and south bridges, and feel whether it is hot, including the power chip, I/O chip, clock chip, etc.

3. Unplug all peripherals of the motherboard, including board card, VGA cable, KB cable, hard disk cable, and leave only The power supply line necessary for the motherboard, then unplug the memory and power on to see if the motherboard has an alarm sound, like 3680, just plug in a buzzer to test

4. If there is no alarm when the memory is unplugged, clear the bios and see if the motherboard has an alarm sound

5. Remove the CPU heat sink or fan, and touch the CPU to see if there is any temperature 6. Re-plug the motherboard

7. Re-plug the CPU

8. Replace the CPU

9. Lightly press the North Bridge, CPU, and South Bridge with your hands

Third:The monitor does not respond after the motherboard is turned on, but there is a memory self-checking sound

1. Check whether the power cord and signal line of the monitor are properly plugged in

2. Check whether there is any material falling off next to the motherboard display chip 3. Boot into the bios and press the Num Lock light on the keyboard to see if it is normally on and off

4. Clear bios

5. Touch the north bridge with your hands, whether it feels unusually hot

6. If there is no display in the system when there is a screen entering the system during the power-on self-test, check whether the host computer cuts the screen, Press Ctrl+Alt+F1/F2/F3/F4 with your hand, or press F8 to enter the safe mode or VGA mode to enter the system to check whether the motherboard displays normally

Fourth:the host cannot enter the system

1. Boot into the bios to see if the hard disk can be found under the bios 2. Check whether the hard disk cable is well connected

3. Listen to whether the hard disk is rotating normally

4. Scan the hard drive with MHDD to see if there are bad sectors

 5. Rewrite the master boot record with diskgen

6. Determine whether the system has a virus

7. Re-do the system

8. Re-do the system after replacing the hard disk 

Fifth: the host screen is turned on

1. Power on and press F8 to enter the safe mode, and determine if it is caused by incorrect driver installation

2. Use the eraser to store the golden finger

3. Use fine sandpaper to clean the memory slot, if there is no sandpaper, plug and unplug the memory several times to test

4. Replace the memory

5. If you replace the memory motherboard and the screen is still corrupted, you can judge that it may be a motherboard problem, replace the motherboard to test