Introduction to DC Working Voltage Measurement Methods
This is a kind of in the case of power on, with a multimeter DC voltage block on the DC supply voltage, peripheral components of the operating voltage measurement; detection IC pins to ground DC voltage value, and compared with the normal value, and then compression of the scope of the fault, to find out the damaged components. Measurement should pay attention to the following eight points:
(1) The multimeter should have a large enough internal resistance, at least 10 times greater than the resistance of the circuit under test, so as not to cause large measurement errors.
(2) Usually turn each potentiometer to the middle position, and if it is a TV set, the signal source should be a standard colour bar signal generator.
(3) The meter pen or probe should take anti-slip measures. Because of any instantaneous short circuit is easy to damage the IC. can take the following method to prevent the table pen sliding: take a section of bicycle valve core set on the tip of the table pen, and long out of the tip of the table pen about 0.5mm or so, which can make the tip of the table pen good contact with the test point, but also effective in preventing slippage, even if it touches the neighbouring points will not be short-circuited.
(4) When measured a pin voltage does not match the normal value, the pin voltage should be based on the normal operation of the IC has no significant impact on the other pin voltage and the corresponding change in the analysis, in order to determine the good and bad IC.
(5) IC pin voltage will be affected by peripheral components. When the peripheral components leakage, short circuit, open circuit or change in value, or the peripheral circuit is connected to a potentiometer with variable resistance, then the potentiometer sliding arm is in a different position, will make the pin voltage change.
(6) If the IC pin voltage is normal, it is generally believed that the IC is normal; if the IC part of the pin voltage is abnormal, it should start from the largest deviation from the normal value, to check the peripheral components have no fault, if there is no fault, then the IC is likely to be damaged.
(7) For dynamic receiving devices, such as television sets, in the presence or absence of signal, IC pin voltage is different. If you find that the pin voltage should not change instead of large changes, the size of the signal and adjustable components with different positions and changes instead of changes, you can determine the IC damage.
(8) For a variety of operating modes of the device, such as video recorders, in different operating modes, IC pin voltage is also different.
