1. The damage resistance characteristics
Resistance is the electrical equipment in the largest number of elements, but not the highest failure rate components. Damage resistance to open the most common resistance becomes large rare, very rare resistance becomes smaller. Common carbon film resistors, metal film resistors, wirewound resistors and insurance resistance several. The first two resistance most widely used, its damage is characterized by one higher low resistance (100Ω or less) and high resistance (100kΩ or more) of the failure rate, intermediate resistance (such as a few hundred to tens of thousands of European Euro) of little damage; the second is a low-value resistor damage is often charred black, it is easy to find, but there are few signs of damage when high value resistors. Wirewound resistors typically used as high-current limiting, little resistance. When cylindrical wire wound resistors and some will be black or burned skin surface burst, crack, some no trace. Cement resistor is a wire wound resistors, when burned may break, otherwise there is no visible trace. Some surfaces will blow up when the insurance resistance burned piece of paper, there is no trace of some, but never scorched black. According to the above characteristics, when checking resistance can be focused, quickly identify damage resistance.
2. The characteristics of electrolytic capacitors damaged
The amount of the electrolytic capacitors in the electrical equipment in the large, high failure rate. Electrolytic capacitor damage are the following performance: First, completely lost the capacity or smaller capacity; the second is mild or severe leakage; the third is the loss of capacity or a smaller capacity both leakage. Find electrolytic capacitors damaged methods are:
(1) See: will leak when some capacitor damage the circuit board below the surface of the capacitor capacitance even the appearance will have a layer of grease, which absolutely can not be reused capacitance; capacitance can muster after some damage, this capacitance can not continue to use;
(2) touch: Some serious leakage of electrolytic capacitors may have a fever after boot, when touched with a finger or even hot, this capacitance must be replaced;
(3) inside the electrolytic capacitor electrolyte, the electrolyte will dry baking time, resulting in reduced capacity, so we should focus on checking the heat sink and high-power components near the capacitor, the closer it, the possibility of damage the greater.
3. Second, transistors and other semiconductor devices damaged features
Second, the transistor's damage is usually PN junction breakdown or open circuit, short-circuit breakdown of which the majority. In addition there are two damaged performance: First, the thermal stability deteriorate the performance of the boot to normal after working for some time, the occurrence of soft breakdown; another is characteristic of PN junction deteriorates, measured with a multimeter R × 1k, Each PN junctions were normal, but does not work if the machine, if the R × 10 or R × 1 low range for testing, will find its PN junction forward resistance larger than normal. Measurement, transistor pointer multimeter can measure the road, more accurate method is: Set the multimeter R × 10 or R × 1 file (usually with R × 10 stalls, is not apparent then R × 1 file) in road test Second, the transistor PN junction positive and negative resistance, if the forward resistance is not too large (relative to normal), the reverse resistance is large enough (relative positive value), indicating that the normal PN junction, on the contrary it is doubtful, to be welded By then measured. This is because, transistor circuits mostly peripheral resistance is generally in hundreds of thousands more in Europe, with a multimeter to measure low resistance profile in the road, you can basically ignore the impact of external resistor PN junction resistance.
4. The integrated circuit damage characteristics
IC complex internal structure, a lot of functions, any part of the damage can not work properly. Damage integrated circuits, there are two: completely damaged, poor thermal stability. When completely damaged, it can be removed with normal measured for comparison with the model of integrated circuits each pin to ground positive and negative resistance, which can always find one or a few pin resistance anomalies. Poor thermal stability, the device can work with anhydrous alcohol cooling is suspected of integrated circuits, time delay or failure if the fault no longer occurs, it can determine. Usually only be replaced with new IC to exclude.
Decade of electronic components engineers share the common characteristic of product failure!
1. The damage resistance characteristics