Laptop motherboard Troubleshooting How to repair

Laptop motherboard Troubleshooting How to repair

First, the motherboard breakdown classification

In general, we can divide the motherboard failure into four categories:

The first category is based on the impact on the computer can be divided into non-fatal and fatal failure of the fault. Non-fatal fault also occurs in the system during the electrical self-test, the general error message; The fatal fault occurs during the power self-test of the system, which usually causes the system to panic.

The second category can be divided into local fault and global fault according to the different influence range. Local fault refers to the system of one or several functions are not normal, such as the motherboard on the printing control chip damage, only caused online printing is not normal, does not affect other functions; Global failures often affect the normal operation of the entire system, causing it to lose all functions, such as the clock generator damage will cause the entire system

Third, according to the failure phenomenon is fixed can be divided into stability failure and instability. Stability failure is due to the failure of components, circuit breakers, short circuit, the failure of the phenomenon of stable recurrence, and instability fault is often due to poor contact, component performance, so that the logic function of the chip is sometimes normal, sometimes abnormal critical state and caused. If the display card is in poor contact with the slot due to an I/O slot distortion, the display is in a variable error state.

Four is according to the influence degree different may divide into the independence fault and the correlation fault. Independent fault refers to the failure of the chip to complete a single function; correlation fault refers to a fault associated with some other faults, its fault phenomenon for many functions are not normal, and its fault in essence for the control of the common part of the function of the failure caused (for example, soft, hard disk subsystem work is not normal, On the hard disk control card, its function control is more separate, the fault is often on the motherboard's peripheral data transmission control namely DMA control circuit.

Main cause of motherboard failure

1, man-made failure: Live plug I/O card, and in the board card and plug when the force improperly caused to the interface, chips and other damage.

2, the environment is bad: static electricity often causes the motherboard chip (especially CMOS chip) to be penetrated. In addition, the motherboard encountered power damage or power grid voltage instantaneous spike pulse, often damage the system board power plug near the chip. If the motherboard is covered with dust, it will also cause a short circuit signal and so on.

3. Device quality problem: The damage caused by poor quality of chips and other devices.

Common methods of motherboard fault checking and maintenance

Motherboard failure is often manifested as system startup failure, screen display and so difficult to visually judge the fault phenomenon. The following list of maintenance methods have advantages and limitations, often used in combination.

1, cleaning method: The brush can be brushed lightly to the dust on the motherboard, in addition, some cards on the motherboard, chip using the form of pins, often because of the oxidation of the pin and poor contact. Use eraser to surface oxidation layer, reseat.

2, observe the law: repeatedly look at the repair of the board, look at the plugs, sockets are skewed, resistors, capacitance pins are colliding, whether the surface is burnt, the chip surface is cracked, the motherboard on whether the copper foil burning. Also want to see if there is a foreign matter falling into the motherboard components. Where there is doubt, you can use the multimeter to measure. Touch some of the chip's surface, if abnormal hair hot, can change a chip to try.

3, Resistance, voltage measurement method: In order to prevent accidents, should be measured before the power supply +5v and ground (GND) between the resistance value. The simplest method is to measure the resistance between the chip's power pins and the ground. When the power plug is not plugged in, the resistance should generally be 300ω, and the minimum should not be lower than 100ω. Then the reverse resistance value, slightly different, but not too large. If the positive and negative resistance is very small or close to the conduction, it indicates that there is a short-circuit, should be examined for short reasons.

There are several causes of such phenomena:

One is the chip on the system board that has been penetrated. Generally speaking, such failures are more difficult to exclude. For example, the TTL chip (LS series) of the +5v connected together, can suck the +5v pin on the solder, so that its suspension, measurement, to find fault film. If the use of secant method, will inevitably affect the life of the motherboard. Second, the board has a damaged resistor capacitor. Third, there are conductive debris on the board.

When troubleshooting the short-circuit, plug in all the I/O cards to measure whether the +5v,+12v and the ground are short. In particular, whether the +12v and surrounding signals collide. When there is a good same type of motherboard on hand, you can also use the method of measuring resistance to measure the doubt on the board, by contrast, you can quickly find the chip fault.

When the above steps are not effective, you can plug the power supply measurement. The +5v and +12v of general power supply are measured. When a voltage value is found to deviate from the standard too far, it can be separated or cut some of the lead or unplug some of the chip to test the voltage. When you cut a lead or unplug a chip, if the voltage becomes normal, then this lead leads to the components or unplug the chip is the fault.

4, the Plug Exchange method: The host system has many reasons for failure, such as the motherboard itself or I/O bus of various card faults can cause the system to run abnormally. The use of the plug maintenance method is a simple way to determine the fault on the motherboard or I/O device. The method is to shut down the plug-in board block by piece, each pull out a plate on the boot to observe the operation of the machine, once the motherboard is pulled out after a normal operation, then the fault is due to the board failure or the corresponding I/O bus slot and load circuit failure.

If the system boot is still abnormal after unplugging all the boards, the failure is most likely on the motherboard. The use of the Exchange method is essentially the same type of plug-in board, bus mode, the same function of the plug-in board or the same model chip mutual exchange, according to the changes in the phenomenon of fault diagnosis. This method is used for easy to plug the maintenance environment, such as memory self-test error, can exchange the same memory chip or memory to determine the cause of the failure.

5, Software Diagnostics: Through the random diagnostics, special maintenance diagnostic card and according to a variety of technical parameters (such as interface address), the Special diagnostic program to assist hardware maintenance can achieve a multiplier effect. The principle of program testing method is to use software to send data, commands, to identify the fault site by reading the status of the circuit and a chip (such as registers). This method is often used to check various interface circuit faults and various circuits with address parameters.

But the premise of this method is that the CPU and the base bus run normally, can run the diagnostic software, and can run the diagnostic card installed on the I/O bus slot. The preparation of the diagnostic procedures to be rigorous, comprehensive targeted, can allow some key parts of the regular signal, can be repeated testing of occasional failures and can display record error situation.