A. to repair the LCD should learn to determine which part is faulty, this is the first step. The following will talk about the main faults and parts of the LCD TV judgment.
1: no image no sound, the power light flashes into a constant light, the screen flashes a white light at the moment of power on. This failure is mostly backlight driver board damage. But also met in the maintenance of the screen is the lamp damage.
2: After a time of power on the screen (mosaic), the sound is normal. This phenomenon is the first is a bad digital board (over the hole does not work or IC contact is not good). The second is a bad contact within the machine connection.
3: boot three no, the power light does not light. The first is a bad power board, the second is the CPU part of the work is not normal.
4: light flashing can not be turned on: CPU bus work is not normal or boot program IC (BIOS) bad, “BIOS” IC and poor contact between the CPU.
5: high temperature: we see the machine in the customer’s home is no more than wall-mounted and pedestal type two placement, but my personal observation, the same model and purchase time the same machine, wall-mounted machine than the chance of failure of the pedestal type, and the same failure also early 1-2 years, so it seems, is related to the temperature, in this case, I repaired the machine will be installed two computer fans to ensure that the warranty period will not be due to High temperature and return to repair.
6: corrosion resistance: in addition to the above-mentioned concert hall, near the kitchen machine than other machines failure rate, and their problems are derived from the corrosion of the metal surface between the connectors, and even lead to double-sided copper eye corrosion, the source of this phenomenon is, of course, the problem of air quality, for the repair of this situation, I use the method of sealing with heat-conductive silicone grease and does not affect the heat dissipation, of course, the connectors The metal should be applied with rubber to apply clean.
7: Almost all the screen will appear black band, bright line problem, repair this fault first to have repair conditions, after the completion of the repair try to use thermal grease coated with more points in the COF module IC because this problem is also caused by the temperature.
LCD TV common failures and repair methods (LCD TV ten common failures)
Second, the common machine and fault phenomenon and troubleshooting methods
1: As mentioned above, the screen problem (black band, bright line) is the most, this situation is generally in the absence of maintenance conditions can not do, only rely on the technology and maintenance conditions.
2: LG screen components of the buffer board is often bad parts of the phenomenon is full of screen miscellaneous points, but also some are full of regular vertical bars, this failure can replace a pair of buffer board (even if a bad side, but also to buy a pair of people will not sell a single to you) or measure out which piece of IC bad, replace it can be.
3: No matter which screen, Y board is in the PDP machine inside the chances of bad accounted for the second, it is generally damaged after the phenomenon is the screen, full of color dots, or due to short circuit and power protection, VS or VA voltage instantly, but not up to the screen voltage value of the table specific why easy to bad, I do not know a reason.
4: X board is also a PDP machine often bad components, its performance for the boot protection (Fujitsu screen mostly), and brightness dark.
5: The failure rate of the logic board is not low, in the PDPLCD are more common, its performance is mostly screen light, but there will be no characters, no image, or image irregularities chaotic color, lack of color, negative image, etc. Some can not be turned on.
6: LCD more common failures are screen problems, dark bands, lines, is the most common, these basic can be summarized as screen problems, some to have repair conditions to repair, some because of the high temperature, resulting in COF and screen connection point of the ACF out of this phenomenon can be repaired with a flat iron below the pad insulation media hot method
7: LCD machine, the screen component inverter circuit (high-voltage board) is a fault-prone parts, manifested as a light on, but a while no light, but there is sound, (except SHARP), but the light tube aging and damage will lead to high-voltage board protection, to determine whether the light tube or the high-voltage board itself is bad, the elimination of the high-voltage board on the average value of the comparative feedback circuit.
8: Many friends ask how to maintain the SHARP LCD, in fact, and ordinary LCD is similar to enter the maintenance menu, you can see the error items there are fault codes, some directly to the code zero, some have to repair the corresponding parts of the fault.
Third, the LCD TV backlight common fault judgment
1. the backlight in the AC power-on instant LCD screen light a little off, at this time, the accompanying sound, remote control, panel button control functions are normal This phenomenon is caused by backlight circuit protection, the reason for the backlight booster board power supply abnormal for CCFL backlight circuit, if a backlight tube open circuit (common for the backlight booster board lamp socket open solder or socket is not inserted tightly caused by circuit protection) or A broken lamp can cause the above failure.
2. the backlight switch no change, with the sound, remote control, panel button control are normal this fault need to detect the following working conditions.
(1). the backlight booster circuit power supply, common large screen for 24 volts, very few with 120 volts, small screen is generally 12 volts.
(2). the CPU control circuit output backlight booster board oscillator work switch control signal, common for high level start, more 3V-5V lamp lighting control signal if the above working conditions are available, then you can replace the backlight booster board, if the replacement backlight booster board failure as at the beginning, mostly for the LCD screen components in the backlight tube damage.
3. when the backlight is bright and not bright, it is common that the lamp socket of the backlight booster board has poor contact with the lamp, and the backlight power supply is high or low.
Post time: Aug-04-2022