What is this circuit board called and how to use it to repair a computer? Details, thank you!

1. Tools and materials required.

The soldering tool needs to have a 25W copper head small soldering iron, and if possible, a soldering station with adjustable temperature and ESD protection can be used, and the tip of the soldering iron should be thin, and the width of the top should not be greater than 1mm. A pair of pointed tweezers can be used to move and hold the chip and inspect the circuit. Also prepare fine welding wire and flux, isopropyl alcohol, etc.

The purpose of using flux is mainly to increase the fluidity of the solder, so that the solder can be pulled with a soldering iron and smoothly wrapped around the pins and pads by the action of surface tension. Remove the flux from the plate with alcohol after soldering.

Second, the welding method.

1. Before soldering, coat the pad with flux and treat it with a soldering iron to avoid poor tinning or oxidation of the pad, resulting in poor soldering, and the chip generally does not need to be treated.

2 Carefully place the PQFP chip on the PCB board with tweezers, taking care not to damage the pins. Align it with the pad and make sure that the chip is placed in the correct direction. Adjust the temperature of the soldering iron to more than 300 degrees Celsius, dip a small amount of solder on the tip of the soldering iron, press down the chip that has been aligned with the tool, add a small amount of flux to the pins at the two diagonal positions, still press down the chip, and solder the pins on the two diagonal positions to make the chip fixed and unable to move.

Re-check the position of the chip after soldering the diagonal. If necessary, it can be adjusted or removed and realigned on the PCB.

3 When you start soldering all the pins, you should add solder to the tip of the soldering iron and apply flux to all the pins to keep the pins wet. Touch the tip of the chip to the end of each pin of the chip until you see the solder flowing into the pins. When soldering, keep the tip of the soldering iron parallel to the pin to prevent lapping due to excessive soldering.

4 After soldering all the pins, wet all the pins with flux to clean the solder. Suction excess solder where needed to eliminate any shorts and laps. Finally, use tweezers to check for false soldering, and after the inspection is complete, remove the flux from the circuit board, and carefully wipe the stiff brush soaked in alcohol in the direction of the pin until the flux disappears.

5. The chip resistor-capacitance element is relatively easy to solder, you can first point tin on a solder joint, then put one end of the component, clamp the component with tweezers, solder one end, and then see if it is corrected; If it is already in place, solder the other end. It takes a lot of practice to really master the art of welding.

Take the problem of repairing the computer motherboard not lighting up as an example.

Diagnose the card first and detect whether there is a short circuit.

Then on the multimeter, check whether the capacitor and diode are short-circuited.

I know these things so far, the master doesn't want to teach me deeply, I'm very depressed, these are often learned by watching the master's operation.

Study hard.

1. Contrasting method. The wide call ratio method is a commonly used circuit board maintenance method, which can compare various parameters such as current, voltage, resistance, VI curve and so on from a single component, unit circuit, whole board and whole equipment to quickly and effectively determine circuit board faults.

2. Current method. The galvanic method is generally used to check the load current of the circuit board. In actual maintenance practice, if there is the same circuit board maintenance, by using the maintenance power supply to power the board, sometimes the current is very intuitively seen, so that the approximate fault situation of the circuit board can be quickly locked, and it can also be used as a basis for judging the circuit board maintenance results in the absence of test conditions.

3. Substitution method. Use the same specification of good performance of the component to replace the suspected faulty components, through the replacement before and after comparison, to determine the fault method, if after the replacement, the fault phenomenon is eliminated, it means that the replaced component has been damaged.

4. Voltage method. It is one of the most widely used methods to check for circuit board faults, which finds the fault point by measuring the voltage of the main endpoint in the circuit board and the voltage of the key components, and comparing it with normal values. It is simple and effective, especially in some cases where the test conditions are not available.

For example, DAC chips, under general conditions, there is no way to test its performance, at this time, the test of this chip, after excluding the short circuit, you can test whether the VCC power supply and reference voltage of the chip are normal, and roughly judge the quality of the chip.

5. Resistance method. The resistance method is to use various instruments to measure the resistance value of suspicious points, suspicious components and pins of the chip to the ground in the circuit board, and compare the measured resistance value with the normal value, so that the fault can be quickly found. Generally, you can use multimeters, digital bridges and other equipment to measure the resistance value, ** or offline resistance value.

Obviously, the measurement will be affected by the components connected in parallel, resulting in deviations in the measured values, and the components can be desoldered from the board for offline measurement.

6. There are many maintenance methods for circuit boards, and the formation of each method depends on the accumulation and summary in ordinary practice. Mr. Guan found that some students often have some whimsical ideas in the actual circuit board maintenance to solve the fault of the circuit board sent by the customer for repair, which is simple and effective. These impromptu repair methods are a valuable experience when solving certain boards and certain types of failures.

Practice more maintenance, and over time, you will accumulate a lot of your own methods.

**The measurement method is generally used in the mass production of circuit board manufacturers, manufacturers in order to facilitate maintenance, generally build a more general debugging and maintenance platform, which can easily provide the power supply required by the circuit board and some necessary initial signals. **The measurement method mainly solves two problems. The first is to break down the problems found in the previous two steps and finally lock down to the component that has the problem.

Step 1: Power on the circuit board, In this step, it should be noted that some circuit board power supply is not single, it may need 5V, plus or minus 12V, 24V, etc., don't leak the power supply that should be added. After the circuit board is powered on, touch the components on the circuit board by hand to see if there are hot and hot components, focus on checking the 74 series chips, if the components are hot, it means that the components may have been damaged.

After replacing the components, check that the board ballow fault has been resolved.

Step 2: Use an oscilloscope to measure the gate circuit on the boardto see if it conforms to the logical relationship. If the output does not conform to the logic, it needs to be treated separately in two situations, one is that the output should be low-level, and the actual measurement is high-level, which can directly judge the chip damage; The other is that the output should be high, and the actual measurement is low, and it cannot be judged that the chip has been damaged, and the chip needs to be disconnected from the back circuit, measured again, and observed whether the logic is reasonable, and judged the quality of the chip.

Step 3: Use an oscilloscope to measure the crystal oscillator in the digital circuitto see if it has an output. If there is no output, it is necessary to remove as much of the chip connected to the crystal oscillator as possible before measurement.

If there is no output, it is preliminarily judged that the crystal oscillator has been damaged; If there is an output, you need to put the removed chips back one by one, and measure one by one to find out where the fault is.

Step 4: Digital circuit with bus structureGenerally, it includes three channels: number, address, and control bus. Use an oscilloscope to measure the three buses, compare the schematic diagram, observe whether the signal is normal, and find out the problem.

The Yubei Kai line measurement method is mainly used for the comparison of two good and bad circuit boards, through the comparison, to find problems and solve problems. So as to complete the repair of the circuit board.

Summary. Hello, dear, common faults on the circuit board The common faults on the circuit board are: 1: The electronic components on the circuit board (resistors, capacitors, inductors, diodes, transistors, field effect transistors, integrated chips, crystal oscillators, etc.) are obviously damaged.

Circuit board issues.

Hello, I am a high-quality teacher, I am honored to answer your questions, it will take a little time to sort out the answers, please be patient.

Hello, dear, common faults on the circuit board The common faults on the circuit board are: 1: The electronic components on the circuit board (resistors, capacitors, inductors, diodes, transistors, field effect transistors, integrated chips, crystal oscillators, etc.) are obviously damaged.

I wonder what this board is called, and the four wires circled are connected to the camera.

Hello, 1. There are two connectors in the tail line of the general surveillance camera, which are the power plug and the output plug; 2. The round plug is a DC12V power supply plug, which is directly connected to the power adapter to supply power to the camera; 3. The Q9 head is the output plug of the camera, and the male connector is connected to the first wire.

Due to the complexity of the electronic circuit, check whether the input and output of the circuit board meet the requirements, whether the power indicator is on, check whether there are traces of burning on the circuit board, and then use a multimeter to detect each electronic component until it is normal, and then use a false load to power on the test. You can visit www.iuiang.com for advice.

Find the fault site first, then find the faulty component, confirm it, solder it with an electric soldering iron, and then confirm it again with a multimeter. After confirmation, the good device can be soldered. At this point, the repair work is basically over. All that's left is assembly restoration.

1. First of all, we must understand the role of the circuit board;

2. Observe and analyze the distribution of components on the circuit board and the use of components in the circuit board;

3. Whether there are obvious burned out electronic components;

4. Find the information of the damaged components to determine the role of the components in the circuit;

5. Remove the damaged components for testing to determine their quality;

6. Check the components around the damaged components and judge their quality;

7. Replace all damaged components, and use the power supply that can limit the current to adjust the current from small to large to power the repaired circuit board for power-up test.

8. If the power can be turned on normally, and there is no heating phenomenon, the board can be installed on the machine for testing.