Function and Parameter Testing
1. The <Tester> can only detect the device in the cutoff, amplification, and saturation regions. However, it cannot measure specific values such as the working frequency and the speed of operation.
2. Dongguan PCB Repair Company Analysis: Similarly, for TTL digital chips, it is only possible to know the output changes of high and low levels, but the speed of the rising and falling edges cannot be determined.
Crystal Oscillator
1. Typically, only an oscilloscope (the crystal oscillator needs to be powered on) or a frequency counter can be used for testing; multimeters and the like cannot measure it; otherwise, the substitution method must be employed.
2. Common issues with oscillators include: a. Internal leakage, b. Internal open circuit, c. Frequency deviation due to deterioration, d. Leakage in the surrounding capacitors connected externally. In this case of leakage, the VI curve of the〈tester〉should be able to detect it.
3. Two judgment methods can be used during the whole board testing: a. The chips near and around the crystal oscillator fail during the test, b. No other fault points are found except the crystal oscillator.
4. Dongguan PCB Repair Company Analysis: Crystal oscillators commonly come in two types: a) two pins, b) four pins, with the second pin being for power supply. Note: Do not arbitrarily short-circuit.
V. Distribution of Fault Phenomena
Partial statistics of circuit board failure locations:
1) 30% of chips are damaged
2) 30% of discrete components were damaged.
3) 30% Copper Wires on PCB Boards Breakage
4) Software destruction or loss up 10% (with an upward trend)
2. As can be seen from the above, when a circuit board in need of repair has issues with wiring and programming, and there's no good board to reference, neither being familiar with its wiring nor able to find the original program, the likelihood of successfully repairing the board is rather low.
