Common element, device fault characteristics and detection methods - Database & Sql Blog Articles

Table 1 common elements, device fault characteristics and detection methods

Name damage condition Fault feature check method Resistance blown (open circuit), short circuit, surface coking, blackening, reference multimeter measuring resistance are ∞, 0 resistance value change bad contact line loose, film layer off fuse resistance with multimeter measuring resistance respectively For ∞ or greater than nominal melting, variable surface coking, color change value multiple times thermal sensitivity, varistor open circuit, short circuit, contact multimeter measuring resistance are ∞, 0, resistance is not bad, metamorphic surface coking, deformation stable, Resistance change law is not normal Potentiometer open circuit, short circuit, bad contact of the moving piece, partial damage, surface oil adhesion, deformation, measuring resistance with a multimeter are respectively ∞, 0, the resistance value does not rotate, the noise is stable, the resistance value Abrupt or abnormality of abnormal carbon film loss capacitor leakage, breakdown, internal view in the circuit for large capacitance (>0.01μF) with a multimeter detection, open circuit, short circuit, contact power, image, sound, etc. The amplitude of the wobble increases with the capacity; the smaller the capacitance (<5 000pF=detected with the appendator or the good capacitor, the difference in the capacity changes, the check Capacitor breakdown, serious leakage, electrolytic capacitor leakage, failure, measuring resistance with a multimeter is ∞ or 0, charge and discharge disconnection, capacity significantly reduces sealing expansion or dryness is not obvious or no charge and discharge phenomenon, stable resistance is small inductance Burning, disconnection, contact surface coking, lead activity using a multimeter to measure resistance is ∞ or when broken, bad internal crystal break or vibration transformer can not work normally. , silent and clutter and test with a multimeter to test the input resistance is very small, the output voltage is very low or voltage fluctuation, with hundreds of picofarad capacitors across the open circuit, internal contact bad "shasha" sound ceramic filter input and output short circuit, resulting in The signal is bypassed or tested by the multimeter. The input/output terminal has a small resistance value or is open circuit (internal disconnection or plating resistance, silver layer is detached). The delay fuse is blown to the naked eye. The filament has been cut off with a multimeter to measure the resistance. It causes intermittent receiving failure. When measuring with a multimeter, the time is broken, the leakage resistance is small, and when the contact is poor, the switch can be turned on multiple times to see if there is any fault. Oxidation with cleaning contacts is a common cause of repairing plugs, sockets, poor contact contact corrosion or loose, by the use of drying method for maintenance. CRT tube seat is prone to leakage, lake or scale makes focusing, acceleration voltage is not high integration The circuit has many functional circuits, and the on-line measurement of each pin voltage, ground resistance and single block partial damage with low withstand voltage and poor overload capability, the resistance value between the IC feet, compared with the nominal value can be found as long as the fault Part of the damage will be scrapped printed circuit board solder joint copper foil off, reference magnifying glass can be observed with a multimeter for the on-off inspection line silver bar break fasteners screw loss, buckle damage affects the machine, wire positioning inspection has a regular release Well, timely reset the broken transformer core disconnection, partial short circuit, overload burnt burnt smell, can be found through the cut-off inspection, disconnection, primary and secondary short-circuit faults, using the touch temperature method can be found partial short circuit, can also be used to replace the initial test Class breakdown, easy to break the tide, break the wire, and visually check the coil and the casing. It can be found that the magnetic core is checked by the multimeter for fault short circuit, core chip loosening and chipping switch. Open circuit (broken wire), leakage, and visual damage may cause an open circuit fault to be detected by an open multimeter. It is judged whether the short circuit is off, the power supply is stopped, the fuse is burned, etc. The replacement of the coil core can be broken, and the visual inspection of the deformation can be found. Trouble with a multimeter to verify the magnetic core break, short circuit with the shell, visual inspection can be found with a multimeter test pole resistance value is O, respectively. . Core chipping, sliding buckle Maintenance case 1: The characteristics of poor contact or virtual welding and the elimination of the cause of electrical failure In addition to the element and device quality factors, the main problem is the process. According to relevant statistics, 44% of the faults are caused by the virtual welding and the loose connection. Caused by poor contact between the plug and the plug, such as broken parts of the larger device, open circuit, desoldering, and silver strip breakage of the printed circuit board. The fault phenomenon is good or bad, and there are intermittent occurrences. It can be found by touch method during maintenance, or it can be eliminated by re-welding. Maintenance case 2: - Elimination of electronic watch failure. The electronic watch sometimes shows that the faults that are sometimes stopped are related to the movement of the movement due to moisture or dust. For this, we can open the back cover, unscrew the fixing screws of the watch core, take out the circuit board, conductive rubber and LCD screen together. In a small container with alcohol, dip it with a soft brush for two minutes, then dry it under the bulb, install it, and the fault can be eliminated. Maintenance Case 3: - Elimination of Induction Cooker Failure. The failure phenomenon of an induction cooker is to burn the fuse tube when starting up. The similar fault is often the breakdown of the rectifier bridge or the high-power switch tube. After the inspection, the high-power tube is broken down. After replacing the parts, the fuse of the same specification is replaced, and the power-on observation is normal. Overhaul Case 4: Elimination of a water dispenser failure. When a water dispenser is energized, the "heating indicator is on", but not heated, the resistance detection method finds that the heater is open, thereby judging that the heater has burned out. Replace the heater of the same specification with normal power supply and troubleshoot.