康佳电视维修实例KonkaTVrepaircase.doc

康佳电视维修实例(Konka TV repair case)
Konka LC-TM2018 LCD TV showed a black screen and silent categories: electronic synthesisevel output, the foot is low, so that the N802 internal S, D switch, to ensure that the ten 12V power supply. In the standby state, the N803 pin output low level, the N804 pin is high, so that the S and D internal N802 disconnect, cut off the power supply of +12V digital circuit, the machine is in a standby state. When normal power on, N812 (MP1410ES) leads N802 to output +12V, after the N812 internal step-down voltage stabilizing processing, outputs the skillful V stable voltage. Digital signal board power supply N407 microprocessor and other components of the image are respectively 3. 3V and 1. 8V, so +5V need to go through N810, N811 respectively, two groups of 3. 3V regulated output power supply voltage, the N812, N813 two 1. 8V power supply voltage regulator output. For the maintenance of digital circuit boards, first of all, check the output voltage of each group is normal. After the above analysis, the +12V supply voltage is measured, the output voltage of the power supply is normal, and the digital signal circuit board has no 3. 3V and 1. 8V voltage. This shows that the N802 or N803 and the peripheral circuit have problems. The measurement of the N802 foot is always high, and then measured N803 (7 feet is always low, check its peripheral components were found no problem, carefully use a magnifying glass to observe N802, N803 each foot solder joints, find a circle around the crack, N803 and foot fault estimation resulting, due to N803 and feet around the crack cause in the open state, and between the foot and the circuit board caused by N803 and the foot has been at a low level, which is in a standby state caused by the fault. Good N803 and re welding feet, try machine troubleshooting.
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