Use the frequency file to repair the LCD TV does not boot 1 case - android - Phones Developers

Filter 18.432M

I recently worked on a 22-inch ENVISION brand LCD TV manufactured by Fujian Jielian Electronics Co., Ltd. The main issue was that the red indicator light would turn on after power-on. When the standby button was pressed twice, the red light turned off, and the green light started to flash before going out again. Then the red light came back on, and the TV returned to the standby mode. At first glance, it looked like the power supply couldn't handle the load. I used a multimeter to check the 5V and 12V output voltages from the IP board, and both were within normal range. But I suspected there might be an issue with voltage ripple, so I decided to check further. Using the frequency function of the multimeter, I found no frequency on the 5V output, but when I checked the π-filter front end, there was a noticeable frequency signal. This indicated a problem with the filter capacitor. I replaced the faulty 16V/330UF π-type filter capacitor and tested the TV again. It worked perfectly after the replacement. However, when I tested the original faulty capacitor with a pointer meter, it showed a normal swing. A digital multimeter capacitance test showed it had 321.6 UF, which is close to its rated value, but still not enough for proper filtering. These types of issues can often be tricky because the capacitor may look fine at first glance but still cause instability in the power supply. This case shows how important it is to test components not just for their nominal values, but also for their performance under real operating conditions. Below are some images related to the repair process:

TV model

Frequency value measured at fault

Replace faulty component

Normally measured frequency value

The picture after the TV is working normally.