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Several principles of circuit board maintenance

Shenzhen Inno Circuit Co.,Ltd | Updated: Jun 08, 2018

Several principles of circuit board maintenance


Electronics technicians have deep knowledge of the maintenance personnel and are full of confidence in circuit board maintenance. So what can be done to better improve maintenance efficiency?

This is a few principles to be discussed below for the reference of the peers. Order the maintenance work orderly and in order.

       Principle one: look after the amount

The circuit board to be repaired must first be subject to visual inspection. If necessary, it must be observed with the aid of a magnifying glass.

      Mainly to see:

      1. Is there a broken wire or short circuit; in particular, whether the printed circuit board connection on the circuit board has broken adhesion or the like;

      2. Is there any disconnection in related components such as resistors, capacitors, and inductors?

      3. Has anybody repaired any components that have been operated? Is there a problem such as the presence of a false-weld solder joint, incorrect insertion, or reversed insertion?

      After eliminating the above conditions, first use a multimeter to measure the resistance between the power supply of the circuit board and the ground. Usually, the resistance of the circuit board should not be less than 70Ω. If the resistance is too small, it is a few or a few dozen ohms. If the device is broken down or partially broken down, measures must be taken to find out the breakdown of the component. The specific method is to power the repaired plate (note! This time, it is necessary to find out the voltage and voltage of the working voltage of the plate. The negative polarity can not be connected wrongly and added above the working voltage value. Otherwise, the circuit board will be damaged! The old fault has not been eliminated and new faults have been added!!) The temperature of each device on the circuit board is measured by the temperature meter, and the temperature rises. The faster the higher is regarded as the focus of skepticism.

      If the resistance is normal, then use a multimeter to measure the resistance of the container, such as the two- and three-electrode FET and strip switch. The purpose is to first ensure that the components being measured are normal. The general test tool can be used. Do not complicate the problem (such as a multimeter, etc.) solved.

      Principle two: first outside and then inside

      If the situation allows, it is better to have a good circuit board as the reference board to be repaired. Then use the tester's dual 梆VI curve scanning function to perform good and bad comparison test on the two boards. The starting comparison test point can be from the circuit. The port of the board starts; then the comparison test between the capacitor and the capacitor is performed on the meter and the meter. This can make up for the inability of the multimeter to detect whether the capacitor is leaking.

      Principle 3: It is difficult after the first

      In order to improve the test effect, the board should be subjected to some technical processing before online functional testing to minimize the influence of various interferences on the test process. The specific measures are as follows:

      1. Preparation before testing

      The crystal short circuit (Note to the four-pin crystal oscillator to figure out that the two feet for the signal output pin can short-circuit the two feet. Remember that under normal circumstances the other two feet for the power pin must not be shorted!!) For large-capacity electrolysis Capacitors also have to be soldered to make them open, as the charging and discharging of large-capacity capacitors will also cause interference.

      2. Use the exclusion method to test the device

      During the on-line test or comparative test of the device, any device that passed the test (or more normal) should directly confirm the test result to the record. If the test fails (or exceeds the tolerance), it can be tested again. If it still fails, The test results can be confirmed first. This will be tested until the device on the board is tested (or compared). Then those devices that failed the test (or more out of tolerance) are processed.

      For some devices that fail to pass the online test, some test instruments also provide a less formal but more practical processing method: since the test instrument supplies power to the circuit board, it can also be applied to the corresponding power supply and ground of the device through the test clamps. If the device's power pin is cut off at the foot of the device, this device will break away from the circuit board power supply system.

      At this time, the device is tested for on-line function; other devices on the circuit board will not get power to eliminate interference. The actual test results at this time will be equivalent to "quasi-offline test". The accuracy rate will be very high. improve.