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Maintenance of common failures of liquid crystal display

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1 monitor the whole machine without electricity
(1) power supply fault: This is a should be said to be very simple failure, the general liquid crystal display
And the external power supply of two kinds, the machine outside the common. Regardless of the power supply, its structure is much simpler than the power supply of the CRT monitor, vulnerable to the general is a number of small components, such as the insurance tube, rectifier bridge.300V
Filter capacitor, power supply switch tube, power supply management IC, rectifier output diode,
Filter capacitor.

(2) the driver board failure: driver board burn insurance or voltage regulator chip failure, there are some of the machine is the switch power supply, the output of two groups of power, one of the
5V, for signal processing, the other group is provided by 12V
12V, or drive high-pressure plate for backlight, if switching power supply circuit fault may lead to two groups of power are not output. Check the 12V voltage is normal or not, follow check 5V voltage is normal or not, as the A / D board MCU chip voltage is 5V, so the search can not open the machine fault, first million by meter to measure the voltage of 5V, if not 5V voltage 5V voltage becomes very low, then a is power supply circuit input stage the problem is converted to 5V power supply part of the problem, this failure is common, check the 5 terminal voltage block (common types of 8050SD lm2596 AIC15-01.

Another possibility is that the 5V load increased, the 5V voltage is very low, which is another way of saying that, after the signal processing circuit is a problem, there are parts of the circuit damage caused by load increase, the 5V voltage is very low, one by one investigation level after the problem element replacement off the faulty components, 5V can recover, failure to solve general, are often faced with the voltage of 5V returned to normal after the boot is not normal, this situation also have a variety of reasons, one is the MCU program has been obliterated may lead to not boot, there is MCU itself is damaged, such as MCU and I/O the MCU scan can not damage, buttons, the trouble caused by MCU, to find the hardware problem is of no use, even if you change the MCU can not solve the problem, because MCU is the need for programming and writing code, there is no way to find To the original AD driver board to replace the case, with the universal A/D driver board we have substitution such as 151D or 161B.

2 the screen is not bright, but the power indicator light green light. This problem is generally caused by abnormal high voltage, is to protect the circuit action, in this case, the general LCD screen is displayed, see
Method is "strabismus"". Overhaul of the method can be used for single lamp high pressure plate connected to a tube test, because, now the liquid crystal
The design of the high pressure plate of the display is generally symmetrical design, and the two sides are not likely to have a bad. In general, the problem of the old machine is the power of a certain way, the booster tube, the voltage transformer and lamp short circuit or no-load, and the power supply management IC load balance protection,
Many beginners
That replacement is very complex, it is actually very simple, only need to four signal received high-pressure plate can be: 1. Power. 2. To. 3, the switch control ON/OFF. 4, to adjust the brightness of ADI. First determine the power line of the cathode and the anode and fuse in general is the cathode, anode is connected to the negative terminal of the capacitor. Then determine the voltage, voltage to determine the best way is capacitance marker, if 6V around it is 3.3V, if capacitor superscript 12V around, then the input voltage must be
5V
, if it is about 24V or above, then is 12V, 310-311 analogy, the capacitance on the subject of voltage divided by two, the closest a few volts is a few volts the. Some people said in this connection the
And still does not shine, or just flashed destroy, is have a lot of high-pressure plate is more than this, how to do it? Find control foot, see the foot is received on a small transistor is generally directly receiving triodes, up in the middle of a small capacitor
, it should be very easy to identify, the control of the foot is generally
3.3V and
5V, there are also individual grounding, so we do not know the case, the first pick to try, no longer then 3.3V
5V, if the input voltage and control voltage is more than 3.3V
The situation is
, can be directly combined with the extra foot how to do it?????
, you don't have to deal with it.

3 display screen, no backlight. The power light green light.
Strabismus LCD screen display image, belongs to the power supply circuit of high-pressure plate. Key check the 12V power supply (fuse f) and 3V or 5V voltage switch is normal. If because of the MCU caused no output voltage control switch, can be extracted directly instead of three terminal voltage stabilizing block AIC1084 3.3V. Repair of high pressure plate (power fuse ideas - control switch - power management IC---- push-pull bassoon - power switch tube ----DA conversion circuit (inductive storage, rectifier tube) ---LC booster circuit, a step-up transformer, the boost capacitor) -- coupling capacitors - lamp tube.
4 screen bright line, bright or dark with this kind of problem, is generally the fault of LCD screen. Bright line fault is generally connecting cable LCD screen body out of the problem or a row and column driver IC damage. The dark line is the body of the screen there is leakage, or tab flexible plate connection open. Of the above two kinds of problem basically is to machine sentenced to death the, no maintenance value, because the price of a screen is too high.   
5. Take a screen or white screen of this problem is generally screen driving voltage is out of the question, to change the drive plate and screen line displacement test, if no way to check the screen back plate power supply circuit, maintenance ideas: drive in 5V turn 3.3V voltage stabilizing block AIC1084 whether power supply output. --- screen driver board insurance wire (f) - 3.3V -----DC-DC conversion circuit, negative pressure is formed the IC (-7V) ----, column driver IC.
6 color fault can enter the factory adjustment mode adjustment. If there is no this mode and ideas of the maintenance: the replacement of screen line and an adapter board ----- rewrite driver program -- driving in bad (less common) -- screen backboard control IC bad (less common) -------- unplug the screen line observation backlight color (flat backlight color lamp aging) ---- for the lamp.
7 character virtual or trailing
Maintenance ideas: check VGA signal line, look at the focus r.g.b. three lines of wire are connected normal -- replace screen wire or adapter plate -- rewrite driver program -- change the driver in ----LCD screen backboard signal interface IC bad -----LCD screen backplane contrast potentiometer adjustment ------LCD screen guide plate and displacement, polarizer dislocation.

8.LCD screen inside stain
Ideas of the maintenance: cleaning or replacement for protective film -- open screen cleaning outer polaroid and organic glass (with a cotton ball, pure water treatment) - dryer hairdryer
9.LCD screen leaked or uneven light
Maintenance ideas: re install the lamp, the light guide plate adjustment
10.LCD screen highlights
One or two big bright spot, you can try to gently with a fingertip pressure highlights, disappeared, indicating that for the pixel switch tube and electrode virtual connection. Small black spots and dots have internal guide plate or polarizer has caused the dust may be. Can be cleaned.
The above method to take the first customer agrees that during the trial, before the operation, otherwise the consequences themselves, all the responsibility and the author.
11.LCD screen brightness low
Check the pressure plate to adjust the brightness of ADJ circuit for the lamp - - change the pressure plate, adjust or replace the light guide plate
12: error "out of range"
Check the signal line: Rewrite MCU driver EPROM program - - to replace the EPROM------ rewrite driver board for
13: electricity does not press the switch button and white screen backlight, button image can be displayed properly
Reactions high-pressure plate interface switching signal and the adj pin signal created the earth, part of the MCU board the switch signal output driver is not normal, can rewrite the program of the MCU repair. For MCU