In the absence of any schematic conditions to a relatively unfamiliar circuit board maintenance, the previous so-called "experience" will be difficult to do, although the deep hardware of confidence in maintenance, but if the method is not appropriate, work will be twice as effective. So what can be done to improve maintenance efficiency? The following steps should be followed in an orderly manner.
Method 1: look before you measure
Tools: multimeter,
When holding a circuit board to be repaired, good practice is to first make eye measurements of it, and if necessary, what to look at with the help of a magnifying glass
Basically see:
1. Whether there is a break;
2. When force components such as resistance, electrolytic capacitance, inductance, diode and triode are disconnected;
3. Is there any break or adhesion of the PCB connector?
4. Has anyone ever done it? Which components have been moved? Whether there are operating errors such as virtual welding, leakage welding, plug reversal, etc.;
After determining that the circuit board is repaired without the above conditions, the resistance value between the circuit board power supply and ground is measured with a multimeter first. Above, if the resistance value is too small, just a few or a dozen ohms, indicating that the circuit board has components on the breakdown or partial breakdown, must take measures to find out the breakdown components. The specific method is to supply power to the repaired board and touch the temperature of each device on the circuit board by hand. If the resistance value is normal, use a multimeter to measure the resistance, diode, audion, field effect tube, dial switch and other force components on the board. The purpose is to first ensure that the measured components are normal
Method 2: outside first
Usage tool: circuit online maintainer
If circumstances permit, the best is to find a piece with the good maintenance board plate as a reference, and then use the twin rod VI curve scanning function of good and bad two boards for contrast test, the starting point of contrast can start on the port, and then, its excellent contrast test, especially for capacitance can make up the drawback of the multimeter online if it is difficult to measure the leakage.
Method 3: easy first, difficult second
Tools: electric circuit maintenance instrument, electric iron, marking pen
In order to improve the test effect, some technical treatment should be done before the online functional test on the circuit board, so as to minimize the negative impact of various interference on the test process. The specific measures are:
1. Preparation before test
Short circuit the crystal oscillator and open the large electrolytic capacitance by welding a foot, as the discharge and charge of the capacitor can also be dry
2. The device was tested by elimination method
In the process of online testing or comparison of devices, please directly confirm the test results of devices that have passed (or are normal) in order to record. If the test fails (or is out of tolerance), it can be tested again. If it fails, the test results can be confirmed first, and then the test will continue until the test (or comparison) of the device on the board is completed, and then the device that fails (or comparison is out of tolerance) can be returned. Does not pass the functional online testing device, instrument also provides a less formal but more practical processing method, because the instrument of power supply circuit board can be applied to the corresponding power supply device with the test and the anchor, power on the device implementation of blade to cut feet, this device will be out of the circuit board power supply system, when the device is online again functional testing, due to the circuit boards of other devices will not cause interference, the actual test results is equal to "offline", the measuring accuracy will be greatly improved.
3. The asa-vi curve scanning test is used to compare the devices not covered by the test library
As the as-vi intelligent curve scanning technology can be applied to the comparison test of any device, as long as the test clip can clip the device, and there is a reference plate, through the comparison test, the device has a strong fault detection ability. This function makes up for the deficiency of the test library in the online function test of the device, and expands the detection range of the circuit board fault by the instrument. Reality often appear unable to find a good board for reference, and the circuit structure of unattended board itself without any symmetry, in this case, the ASA - VI curve scanning the comparison test function, and the function of online test due to the incomplete device testing library, unable to complete the circuit boards every device test again, circuit board will not be able to repair, here is the limited circuit online instrument maintenance, just like no cure-all medicine
