TV motherboard troubleshooting and repair with a multimeter.
Firstly, you need to be able to use a multimeter, and secondly, you need to be able to read a circuit diagram.
In the measurement of the circuit, there are several key points, one is the supply voltage, the second is the current, and the third is the original.
Measure the circuit voltage and current need to have the schematic circuit, according to the schematic diagram of the marked value of the comparison test, if the deviation is large (more than 5%), then we should condense the circuit is not normal, focusing on checking the relevant to go to the circuit of the original.
Measurement of a variety of original words need to understand the characteristics of the original, in order to make a correct judgement.
Notes on the use of multimeter:
(1) in the use of multimeter, should be carried out before the "mechanical zero", that is, in the absence of measured power, so that the multimeter pointer in the position of zero voltage or zero current.
(2) In the process of using the multimeter, you should not touch the metal part of the pen with your hand, so as to ensure the accuracy of the measurement on the one hand, and ensure personal safety on the other hand.
(3) When measuring a certain amount of electricity, you should not change the gear at the same time of measurement, especially when measuring high voltage or high current, you should pay more attention to it. Otherwise, the multimeter will be destroyed. If you need to shift gears, you should first disconnect the pen, shift gears and then go back to the measurement.
(4) When using the multimeter, it must be placed horizontally to avoid errors. At the same time, it should also be noted to avoid the influence of external magnetic field on the multimeter.
(5) When the multimeter is finished using, the changeover switch should be placed in the maximum block of AC voltage. If it is not used for a long time, the battery inside the multimeter should be taken out to avoid the battery corroding other devices inside the meter.
The use of ohm block:
First, choose the appropriate multiplier. In the ohmmeter resistance measurement, should choose the appropriate multiplier, so that the pointer indicates in the middle value of the neighbourhood. It is best not to use the left third of the scale, this part of the scale is very poor intensive.
Second, to zero before use.
Third, can not be charged measurement.
Fourth, the measured resistance can not have parallel branches.
Fifth, the measurement of transistors, electrolytic capacitors and other polar components of the equivalent resistance, must pay attention to the polarity of the two pens.
Sixth, with a multimeter with different multiplication of the ohm block to measure the equivalent resistance of non-linear components, the measured resistance value
is not the same. This is due to the median resistance and fullness current of each block is different caused by the mechanical meter, generally the smaller the multiplier, the smaller the measured resistance value.
