Use frequency meter to repair Sanyo LCD-42CT8 screen interference - android - Phones Developers

Filter 18.432M

Yesterday, a customer sent a 42-inch Sanyo LCD TV. The fault was caused by the whole screen horizontal bar interference. The machine was unpacked and found to have been repaired. Some nails were not installed. The logic board cover was opened and the logic board was found. G-15 has been changed, there is no change in the shaking screen line. In the principle of easy and difficult, the voltage of each group of power supply is normal, and the voltage of the logic board is also normal. In order to separate the fault, the original screen line is pulled from the logic board. Drop, connect the universal board, adjust the screen voltage to 12V, boot, the picture is very good, (so it is very important to repair the LCD with a dot screen or a universal board) Now it is possible to determine the motherboard problem, open the motherboard cover, look carefully, Did not find the circuit board moldy or capacitor drum, the output voltage of each linear regulator IC is also in the normal range, but from the picture point of view should be caused by a certain filter capacitor, but so many patch solid-state filter capacitors, in the end Which one is it? It’s not always taken down and measured. If it’s not broken, it’s possible to tear it down. The repair is in trouble. It’s getting ready to move out of the oscilloscope. I suddenly think that my multimeter can measure. Rate, you can try it. If the power supply has ripples, the frequency meter can be measured. The measurement method is to connect the two test leads to the two ends of the filter capacitor. If you have not measured a few, you can measure the output of the 1.8V regulator IC. There is a frequency of 0.6889MHZ, the other filter capacitors are all 000, so the filter capacitor is removed, the standard is 16V/22UF, the actual measurement is 15.7UF, and a 22UF solid capacitor is turned on, the screen is normal, and then the two ends of the capacitor are measured. Frequency, 000, indicating that the fault has been found, this machine is repaired, see the picture