Common faults and troubleshooting of Philips LCD TV maintenance
1, the whole monitor is dead.
(1) Power failure: It should be said that this is a very simple failure. Generally, there are two power supply modes, internal power supply and external power supply, some of which are more common. No matter what kind of power supply, its structure is much simpler than crt display.
Vulnerable components are generally small components, such as fuses and rectifier bridges. 300V filter capacitor, power switch tube,
Power management IC, rectifier output diode, filter capacitor, etc. Ics commonly used in power boards are: 684 1 203D06. These commonly used pmw chips can be bought in professional LCD accessories stores like me.
(2) Drive board failure: the drive board is burnt out or the voltage stabilizing chip fails. Some machines have built-in switching power supply, which outputs two sets of power supplies, one set of 5V for signal processing and one set of 12V for high-voltage panel point backlight.
If some circuits of the switching power supply fail, both groups of power supplies may not output. Check whether the voltage of 12V is normal first, and then check whether the voltage of 5V is normal. Because the working voltage of MCU chip of A/D driver board is 5V, when the machine can't be turned on, check it first.
Measure 5V voltage with multimeter. If there is no 5V voltage or the 5V voltage becomes very low, then one possibility is that there is something wrong with the input stage of the power supply circuit, that is, there is something wrong with the power supply part where 12V is converted into 5V. This kind of fault is very common. Check the 5-terminal voltage regulator (common model 8050SD-LM2596-AIC15-01,etc.). ).
Another possibility is that the load of 5V is aggravated, and the voltage of 5V is pulled very low. In other words, there was something wrong with the signal processing circuit in the later stage, and some circuits were damaged, which led to the increase of load and the low voltage of 5V. Check the parts with problems in the later stage one by one.
After replacing the faulty component, 5V can be restored to normal, and the fault is generally solved. It is also common that it cannot be turned on normally after the 5V voltage returns to normal. There are many reasons for this. On the one hand, the program of MCU may be washed away, resulting in failure to boot.
In addition, the MCU itself is damaged, for example, the I/O port of the MCU is damaged, which makes the MCU unable to scan the keys.
It's useless to find the hardware problem when encountering the fault caused by this MCU. Even if you change the MCU, it won't solve the problem, because the MCU needs to program and write code. When we can't find a replacement for the original AD driver board, we can only replace it with a general A/D driver board, such as 15 1D or161b.
2. When the display screen is on, it will not light up, but the green light of the power indicator is always on.
This problem is generally that the voltage is abnormally high and the protection circuit is operating. In this case,
Generally, there is a display on the LCD screen, and the way to see it is "squinting". , Philips LCD TV maintenance;
3. The display screen is black and there is no backlight. The green light of the power light is always on.
LCD display image tilt, mostly belongs to the problem of high voltage board power supply circuit. Focus on checking whether the 12V power supply (fuse f) and the switching voltage of 3V or 5V are normal. If the switching control voltage is not output due to MCU problems, it can be directly extracted from the 3-terminal regulator module (AIC 1084)3.3V instead. The idea of repairing high voltage board (power fuse-switch control tube-power management IC- push-pull amplifier tube-power switch tube -DA conversion circuit (energy storage inductor, rectifier tube)-LC
4. The screen is bright, bright or dark.
This kind of problem is usually the failure of the LCD screen. The fault of bright line is generally that there is a problem with the cable connecting the LCD body or the driving IC of a row or a column is damaged. The hidden wire is generally the leakage of the screen.
Or the TAB flexible board opens. The above two problems are basically the death penalty of the machine, which has no maintenance value because the price of a screen is too high. There is a special chip replacement service in Guangzhou, and the cost is very high, so is repair rate.