How to repair the computer motherboard

How to repair the computer motherboard

First, the method of debugging:

1. Will suspect the chip, according to the manual instructions, first check the input, output is the signal (wave type), if there is no out, and then check the IC control signal (clock) and so on, if there is the possibility of this IC bad, no control signal, traced to its former pole until the damage to find the IC.

2. Find the temporary do not remove from the pole can choose the same model. or program content of the same IC back on the top, turn to see if the improvement to confirm the IC is damaged.

3. Use tangent, borrow jumper method to find short route: found some lines and ground, +5v or other IC should not be connected to the foot of the short circuit, can cut off the line to measure, to determine whether the IC problem or the board line of the problem, or from other IC to borrow signal welding to wave-type wrong IC to see if the picture is better, judge the IC's good or bad.

4. Control method: Find a piece of the same content of a good computer board to measure the corresponding IC PIN wave type and its number to confirm that the IC is damaged.

5. Using Microcomputer Universal Programmer (ALL-03/07) (expro-80/100, etc.) in the Ictest Software test IC.

Second, check the Board method:

1. Observation method: There is no burning paste, burning, foaming, plate surface disconnection, corrosion of the socket.

2. Table measuring method: +5v, GND resistance is too small (under 50 ohms).

3. Power check: On the clear already bad board, can slightly adjust high voltage 0.5-1v, after the boot with the hand washboard on the IC, so that the problem of the chip fever, thus perceiving out.

4. The Logic pen checks: to the key suspicion IC input, the output, the control pole each end checks the signal to have no, strong or weak.

5. Distinguish the major work areas: most of the board has a clear division of labor, such as: Control Area (CPU), clock area (crystal oscillator) (frequency), background screen area, action area (people, aircraft), sound generation of synthetic areas. This is very important to the in-depth maintenance of the computer board.

Third, the computer chip disassembly method:

1. Shear footwork: No damage to the plate, can not be reused.

2. Mop Tin Method: In the IC feet on both sides of the welding tin, the use of high-temperature iron to drag back and forth, while the IC (easy to damage the plate, but can be preserved test IC).

3. Barbecue method: In the alcohol lamp, gas stove, electric stove on the barbecue, and so on board tin dissolved after the IC (difficult to grasp).

4. Tin Pot method: In the electric stove for the special tin Pot, after the tin dissolved, will unload on the board of the IC immersed in the tin pot, you can play an IC without damage to the board, but the equipment is not easy to make.

5. Electric wind Gun: with special electric wind gun unloading, blowing to unload the IC pin part, you can turn the IC after the tin (pay attention to the blow plate to shake the wind gun will also blow the computer board bubble, but the wind gun cost is high, generally about 2000 yuan)

As a professional hardware maintenance, board maintenance is one of the most important items. Take over a faulty motherboard, how to determine the specific components of the problem?

Main cause of motherboard failure

1. Human failure: Live plug I/O card, as well as in the Board card and plug when the improper force caused to the interface, chip 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: Due to the poor quality of chips and other devices caused by damage.

Four, cleaning

The first caveat is that dust is one of the biggest enemies of the motherboard. It is best to pay attention to dust, the brush can brush 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 pins and contact poor. Use eraser to surface oxidation layer, reseat. Of course we can use trichloroethylene-volatile performance, is to clean the motherboard of one of the liquids. There is a sudden power off, to turn off the computer immediately, so as to avoid sudden calls to the motherboard and power to burn. Process.

Five, BIOS

Due to improper BIOS setup, if overclocking ... Can jumper clear place, pick reset. If the BIOS is damaged, such as a virus intrusion ..., you can override the BIOS. Because the BIOS can not be measured by instrumentation, it is in the form of software, in order to eliminate all possible causes of the motherboard problems, it is best to brush the motherboard BIOS.

Six, plug Exchange

Host systems have many causes of failure, such as the motherboard itself or I/O bus of various card failures 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.

Seven, watch

Get a defective motherboard first with the eyes sweep, see no burn traces, the appearance of damage, look at the plugs, sockets are skewed, resistors, capacitance pins are collided, whether the surface is burnt, whether the chip surface cracking, 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 universal table to measure. Touch some of the chip's surface, if abnormal hair hot, can change a chip to try.

(1). If the line is broken, we can use the knife cut off the paint scraping clean, in the exposed wire place wax, and then with a needle down the lines to the candle, then the above is dripping silver nitrate solution. Then you will use a universal table to confirm whether the breakpoint is connected properly. Just like this one, the breakpoint is ready. Note that one of the company, do not be impatient, like the motherboard on some places on the line between the distance is very small, can not get a short circuit.

(2). If the electrolytic capacitor, you can find a matching change.

Eight, the universal table, oscilloscope tools

Use the universal table, wave device to measure the power supply of the motherboard components. One is to check whether the motherboard for this part of the power supply, and then there is the voltage is normal power supply.

Resistance and voltage measurement:

The power failure includes the +12v, +5v and +3.3v power good signal faults on the motherboard, the bus fault including the bus itself fault and the bus control power fault, and the fault of the resistor, capacitance, IC chip and other components.

To prevent accidents, measure the resistance between the power +5v and the ground (GND) on the motherboard before powering up. 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:

(1) The chip on the system board 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.

(2) The board has a damaged resistor capacitor.

(3) The board contains conductive debris.

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.

Ix. procedures, Diagnostic card diagnostics

Through the random diagnosis procedure, the special maintenance diagnosis card and according to each kind of technical parameter (for instance the interface address), the custom special diagnosis program to assist the hardware maintenance may achieve the 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.