Measure the positive and negative resistance values ​​between each pin of the IC chip to ground. This is a good IC chip.
Compare to find the point of failure.
2. Online detection
1) Detection method of DC resistance
Same as off-line detection. But pay attention:
(a) Disconnect the power supply on the circuit board under test;
(b) The internal voltage of the universal meter must not exceed 6V;
(c) When measuring, pay attention to the influence of the periphery, such as the potentiometer connected to the IC chip.
2) Measurement of DC operating voltage
Measured DC voltage of each foot of the IC chip can be compared with the normal value. But also pay attention to:
(a) The universal meter must have a sufficiently large internal resistance. The digital chart is preferred;
(b) The potentiometer is rotated to the middle position;
(c) Anti-skid measures shall be taken for the pens or probes, and the bicycle valve core can be used on the pen head.
And should grow pen tip about 5mm;
(d) When the measured value does not match the normal value, the IC chip should be
The constant value has no effect and the corresponding change of other pin voltage is analyzed;
(e) IC chip pin voltage will be affected by peripheral components. When the peripheral leakage, short circuit,
Open or spoilage;
(f) If the IC chip has an abnormal pin, start with a large deviation. First check the external components.
If there is no failure, the IC chip is damaged;
(g) For circuit boards with dynamic signals during operation, no signal IC chip pin voltage is not
However, if the change is not normal, the IC chip may be bad.
(h) The voltage of the IC pin is different for different working modes of equipment.
of.
3) AC working voltage test method
Use a universal meter with a dB range to measure the approximate AC voltage of the IC. If there is no dB
In the file, a 0.1-0.5μF isolated DC Capacitor can be inserted in the positive case. This method is applicable.
For ICs with lower operating frequencies, but note that these signals will be affected by the natural frequency, waveforms are not
The same is different. Therefore, the measured data is approximate and is for reference only.
4) Total current measurement
By measuring the total current of the IC power supply, we can judge whether the IC is good or bad.
Flow coupling, IC damage (such as PN junction breakdown or open circuit) will cause the post-saturation and cut-off, so that
The total current changes. So the total current can be used to determine the quality of the IC.
Resist the voltage, you can calculate the current value.
The above detection methods have their own advantages and disadvantages. In practical applications, it is best to use these methods in combination.
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