LCD color TV repair an example: - appliance repair - Huaqiang electronic network

Probe current voltage pin 420*4450 head diameter 5.0 over current current and voltage pin

MOS power IC full range

Photocoupler

An example of LCD color TV repair:
Machine model: LG-32LH20RC
Fault phenomenon: There is no sound and no image fault repair: When this TV is sent, it is known that the fault phenomenon is: the machine suddenly disappears when the machine is in normal use, only the sound, please correct the sound, even the sound is not there. After disassembling the machine, the color of each function board is relatively new, and the components on the board are not obviously damaged. The voltage of each board input to the main board is measured by a multimeter. The 24V voltage input to the high voltage board is also normal, and the starting voltage of the input high voltage board is also connected. It is also within the normal range between 3.3-5V. Since there is no problem, only the screen line plugged in the main board can be cleaned and removed. The power-on test is as old as the fault. At this time, it is suspected that the high-voltage board transformer short-circuit between the turns caused the lamp point to not light, so the same type of high-voltage board with a multimeter to measure the resistance of the transformer secondary to compare, feel the problem is not like on the high-voltage board. When I was at a loss, I accidentally pressed the remote control TV button and found that the color TV bought the screen with a dark blue raster, and it was stable. Thus firm my good judgment on the backlight system. It is estimated that the problem is still on the screen line, and then the two-terminal interface of the screen line is removed at the same time, the measurement screen line is good, and then the screen line is plugged in and turned on, and the problem is solved. The TV no-signal snowflake point grating appears on the screen, and the color TV is repaired. Everything is normal after trial.
Maintenance experience: If it is difficult to start from the first easy, after the appearance and voltage checks at all levels, immediately check the screen line to take less detours.