I. board checking method:

1. Observation method: there is no burning, burning, blister, plate surface broken line, socket corrosion.

2. Table measurement: whether the resistance of +5V and GND is too small (below 50 ohms).

3. Power on check: for the clear has broken board, can slightly increase the voltage 0. 5-1v, use the IC on the washboard after starting the machine, and let the chip in question get hot, so as to feel it.

4. Logic pen check: check whether or not the signal is strong or weak at the IC input, output and control pole of the key suspect.

5. Identify the major work areas: most of the board has a clear division of labor on the area, such as: control area (CPU), clock area (crystal vibration) (frequency division), background screen area, action area (people, aircraft), sound production synthesis area. This is very important for the deep maintenance of the computer board.

Ii. Troubleshooting methods:

1. Will suspect the chip, according to the instruction of the manual, first check the input, output end whether there is a signal (wave type), if there is no out, then check the control signal of IC (clock) whether there is, if there is this IC bad may * great, no control signal, trace to its previous pole, until find the damaged IC so far.

2. Do not remove from the pole for the time being. Choose the same model. Or the same procedure content IC back on top, boot to observe whether the improvement, to confirm whether the IC is damaged.

3. With tangent, borrow jump line method for short route: see that some letter, + 5 v line and ground or other more IC short circuit should not be connected to the foot, can cut off the line measurement again, judgment is IC or panel line problems, or borrow from the other IC signal welding to the wave type wrong IC on the phenomenon of the picture is good, judge of the IC.

4. Comparison method: find a good computer board with the same content and measure the pin wave pattern and its number of corresponding IC to confirm whether the IC is damaged.

5. Test IC with ICTEST software in microcomputer universal programmer (all-03/07) (expro-80/100, etc.).

Iii. Chip disassembly method:

1. Cut foot method: do not hurt the board, can not be recycled.

2. Towing tin method: solder on both sides of IC foot, use high temperature soldering iron drag back and forth, at the same time out of IC (easy to hurt plate, but can save test IC).

3. Barbecue method: in the alcohol lamp, gas stove, electric stove on the barbecue, such as plate after the melting of tin out of IC (not easy to master).

4. Tin pot method: make special tin pot on the electric stove, after the tin melts, dip the IC to be unloaded on the plate into the tin pot, the IC can be removed without hurting the plate, but the equipment is not easy to make.

5. Electric hot air gun: discharge the chip with special electric hot air gun, blow the IC pin part to be discharged, then the IC after tin can be taken out.

As a professional hardware maintenance, card maintenance is one of the very important projects. Take over a faulty motherboard, how to determine the specific components out of question?

The main causes of mainboard failure are:

1. Human fault: the damage to the interface and chip caused by the improper force when the I/O card is plugged or plugged on the power.

2. Poor environment: static electricity often causes chips (especially CMOS chips) on the main board to be broken down. In addition, when the motherboard encounters power supply damage or the spike pulse generated by the instantaneous power grid voltage, it will often damage the chip near the power supply plug of the system board. If the motherboard is covered with dust, it will also cause signal short circuit.

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

Cleaning first to remind attention is that dust is one of the biggest enemies of the motherboard. Had better pay attention to dustproof, can brush brush the dust on motherboard gently, additional, on motherboard a few insert card, chip USES form of pin, regular meeting because lead oxidation and contact are bad. Use an eraser to remove the oxide layer and re-insert. Of course we can use trichloroethane – volatile, is one of the cleaning liquid motherboard.

There is a sudden power failure, to shut down the computer immediately, so as not to suddenly call the motherboard and power burnt. Process. BIOS due to improper BIOS Settings, if overclocked… You can skip clear, pick and reset. If BIOS is damaged, such as virus intrusion… , you can override the BIOS. Because the BIOS can not be measured through the instrument, it is in the form of software, in order to eliminate all possible causes of motherboard problems, it is best to brush the motherboard BIOS.

There are many reasons for the failure of the unplug switch host system, such as the failure of the main board itself or various card failures on the I/O bus, which may lead to abnormal operation of the system. Using the plug and replace method is a simple way to determine the fault in the motherboard or I/O equipment. The method is to turn off the plug board and pull it out block by block. After pulling out a board, start the machine and observe the running state. Once pulling out a certain board, the main board will run normally.

If the system startup is still abnormal after pulling out all the plug-in boards, the failure is likely to be on the main board. Essentially, the use of switching method is to exchange the same type of plug-in board, the same bus mode and the same function of plug-in board or the same type of chip with each other, and judge the fault location according to the change of the fault phenomenon. This method is mostly used in easily removable maintenance environment, such as memory self-check error, can exchange the same memory chip or memory bar to determine the cause of failure. Watch to get a piece of faulty motherboard first scan with your eyes, see no signs of burnt out, no damage to the appearance, see whether the plug, socket, resistance, capacitance pin touch, whether the surface is burnt, chip surface is cracked, whether the copper foil on the motherboard is burned off. Also check to see if there are foreign objects falling into the motherboard components. When in doubt, use a multimeter. Touch the surface of some chips, if abnormal hot, can change a chip to try.

(1). If the wire is broken, we can use a knife to clean the broken wire paint, in the exposed wire coated with wax, and then use a needle along the line to cut the wax, the next is to drop on the silver nitrate solution. The next step is to use the multimeter to confirm that the breakpoint is connected. So one by one, you just put the breakpoint on. Pay attention to one by one even, do not be impatient, like some places on the motherboard walk the distance between the lines is very small, it will be a short circuit.

(2). If it is an electrolytic capacitor, you can find a matching replacement. Multimeter, oscilloscope tool with the multimeter, wave measuring the main board components power supply situation. One is to test whether the motherboard supplies power to this part. Another is whether the supply voltage is normal. Resistance and voltage measurement: Power supply faults include +12V, +5V and + 3.3v Power supply and Power Good signal faults on the main board; The bus fault includes the bus itself fault and the bus control right fault; Component failures include failures of resistors, capacitors, IC chips, and other components. In order to prevent accidents, the resistance value between the power supply +5V and the ground (GND) on the main board should be measured before charging. The simplest method is to measure the resistance between the power pin of the chip and the ground. Not insert the plug, the resistance should be 300 Ω commonly, also should not be below the lowest 100 Ω. Test the reverse resistance again, slightly different, but not too different. If the positive and negative resistance is very small or close to the conduction, it indicates that there is a short circuit, should check the cause of short.