LCD display Inverter lamp has a direct relationship Inverter typical failure of performance: The LED light is able to control, the host indicator does not light or a light is off. Therefore, it may be Inverter failure, may also be damage to the lamp. According to overhaul the easier issues first principles, should first check the lamp.

 (1) The lamp examination

To use their own separate voltage driver board, each lamp test again, two lines of a light, two lights and four-wire, four-lamp eight lines just take one of the two can be tested. For the six-lane of the four-lamp lamp, take two thick lines of the same color connect can be tested. The particular lamp does not light, the lamp can be determined.

(2) Inverter check

LCD monitor Inverter has two forms: one is a single board structure; another one with the power structure. When the Inverter fails, take a different approach to maintenance.

For veneer Inverter, can be directly replace the entire board, is relatively simple.

One of the one with the power board, you should first check the Inverter power supply fuse, and then check the oscillation transistor, diode, one by one detection method will find the faulty components, replace it. For integrated Inverter maintenance is very difficult, only
Using a separate Inverter substitution. The tube has been damaged. Inverter common troubleshooting.

Inverter common faults and repair methods are as follows:

1) screen instant light immediately after black

Screen instantly lights up immediately after the black failure is mainly caused by poor Inverter feedback circuit. If the voltage is too high lead to protection, the feedback circuit fails, the occur without feedback voltage, feedback current is too large, lamp PIN loose, IC output is too high and other symptoms.

The repair methods There are two:

(1) short connection

General liquid crystal display, pulse width modulation IC pin control or force the output, the pin is shorted to ground its unaffected by the feedback circuit, forced output pulse, both general light boost board, and circuit testing, to find out the point of failure. Note, however, the shorted time can not be too long, otherwise they will be high voltage line is bad, forced output, which led to the ignition or burn Inverter.

(2) comparison test method

LCD monitor left and right lamp with dual output, that is the two lamp corresponding to the same two control circuit that can be used multimeter two circuit testing, and the test results of the two circuits compared, it can be determined whether there is malfunction. But there are also display all the way to control two lamps, you can not use this method.

2) After the power lights but no display

After power lights but no display generally boost board circuit does not generate high pressure caused. Fault There are several reasons:

① 12V to join or the 12V voltage is not normal;

(2) control voltage not joined;

The ③ ground is not normal;

The ④ IC poor, without oscillation, no output;

(5) self-oscillating circuit is faulty.

Should detect whether the step-up board short-circuit fault; detection 12V-to-ground, self-excited tube is breakdown, Ic breakdown. Models for the power section with step-up board lines connected together, no display problems also occur when no power output or abnormal. Maintenance, can be cut to boost part of the power supply circuit, determine the fault lies in the power supply section or in the part of the step-up board to narrow the fault.

3) dim brightness

The dim brightness Failure are the following:

① boost the brightness control circuit board is faulty;

2 12V voltage output is low;

(3) IC output is low;

④ high voltage circuit is not normal.

4) Power light is flashing

Power light blinks and no light, almost no reasons for the failure, the tube is due to the breakdown. In accordance with dull, silent, Figure fault detection and maintenance.

5) graphic display, the screen is dim, red, purple, but the brightness can be adjusted. Do not blink.

Such cases are usually backlight lamp aging, this situation is usually not sudden, usually due to the accumulation of solution only replace the lamp.

6) graphic display screen flicker, no redness, purple screen issue "creak" sound

Such tubes are generally good, because a high-voltage components after working a long Inverter poor contact (usually chip inductors) caused.

7) The screen does not light, but can vaguely see the graphic display

When such a failure occurs bootable listen, if you can hear a "creak" sound, you can determine the lamp power supply circuit or damage to the lamp, you can check the power socket of the lamp; if not open circuit, only to be replaced lamp; if you do not hear a "creak" sound, it may be open or damaged parts on the Inverter is usually a problem with the power supply cable or signal lines, only by means of a multimeter measurement method using a stepwise strategy judgment. the location of the fault.

The Inverter the substitution method

LCD display Inverter is the most common single lamp, dual-lamp, four lights and six lights and wide mouth (mouth) with narrow mouth (mouth) of the points. Inverter operates at high voltage, high current state, the part is easy to aging (in particular the high voltage coil).

1) substitution principle

Inverter substitution Universal Inverter LCD lamp number and size of the interface options, such as four-lamp small mouth LCD screen on the selection of the four light small mouth Inverter. Inverter working conditions, just to find the fault plane 12V, ground and switch control signal 3
Line, and then received a new Inverter can be. 12V power and ground are easy to find, hard to find the switch signal line. Switching signal from the driver board, can be repeatedly press the key to open the panel, measured with a multimeter which wires OV 5V changes, which line is the switching signal line.

Brightness control generally can not receive, the lamp light failure will be excluded.

2) Power the substitution of high-pressure combo plate

The high-pressure part of the power supply high-pressure combo plate damage for the entire board, although convenient, but not economic, and the volume for the one board is not readily available. The following methods can be used: circuit analysis, the original high-pressure part of the device removed and leave space in the original board paste an Inverter be found on the original circuit Inverter required three working conditions, corresponding access to the new Inverter and good insulation protection, the lamp will be lit.

Maintenance notes:

3) Inverter substitution Notes

Inverter substitution should pay attention to the following points.

The ① working voltage to be consistent. The type of liquid crystal display Inverter power supply voltage is not the same. For example, the same dual-lamp Inverter, there are 12V, 14V power supply method, substitution, you should select the input voltage of the Inverter.

(2) backlight number of interfaces and interface style to be consistent. For example, for four-lamp Inverter, try to choose the four-lamp Inverter for substitution, except in special cases, generally do not use the dual-lamp Inverter by changing the output method substitution.

The ③ drive power to match. The power to be the same or higher than the original machine, if the new Inverter power will lead to increased output tube heat, shortened life, or simply can not light the lamp.

(4) installation to the right size. In particular, the volume is not too large, otherwise difficult to assemble.

(5) in installing the Inverter, to ensure that the isolation of the high-pressure part of the display of metallic materials to maintain a distance of at least 4mm, or use of a sufficient level (3kV) insulating material, to avoid high-pressure discharge. In order to avoid interference, must take Inverter edge matching holes screwed to monitor metal shell, inconvenience fixed, but also with thick wire connection.

The performance of the black screen phenomenon of computer LCD monitor LCD screen inside the high-pressure lamp or inverter damage, no display, but the system can not start properly, that the hard disk read data, the operating system can issue start successful music. Connected to the LCD signal cable breakage or poor contact, computer LCD monitor is blank, but vaguely still dim display, the system can also start properly, that hard read data, the operating system can issue start successful music.

Graphics card failure, if it is for this reason, the maintenance cost is very high.

Get the machine to do the initial detection. Connected to a laptop computer CRT monitors external display interface, and then displays the state to switch to the CRT mode, the display is all normal, basically ruled out the possibility of damage of the motherboard and graphics card. But when again to switch back to LCD mode, but it can normally moment, brightness, same as usual, but only for about a few seconds, they become odd dark incomparable. Checked, my initial impression is the motherboard, video card is not bad, vague showed little something LCD and cable is not damaged, it seems likely not lit backlight.

In fact, the LCD itself does not light, adjust the appearing and brightness of the image depends on the adjustment of the backlight brightness. The work of the LCD screen, the light emitted by the backlight through the LCD screen, LCD display thing that catches the eye of love, then we can see the text and images on the LCD display, if you used the microscope, then , saying the principle is similar. If the backlight is damaged, there is no light issue, when we could not see anything. However, if we carefully observe the LCD screen, you will see a faint image display on the LCD screen, then it means that the backlight circuit is broken. This is something like a thin fluorescent tubes like around the back of the LCD, powered and lit by the screen inverter to it, it emits light through the LCD panels, LCD will have a dazzling display.

In general, the backlight is not lit two reasons: the backlight lamp burned or damage to the high voltage circuit driving lamp. The high-voltage circuit board works is the motherboard provides low-voltage direct current through the switch circuit is converted into high frequency high voltage backlight tube lit. It can just press the power button to start the ear against the border of the screen, listen, Zizi sound of clicking, then silent, generally is the problem of high-voltage circuit board, if you have been silent, it may Lamp problem. The judgment in this amateur conditions, though not very professional, but it is quite practical.

Liquid crystal display machine no electricity is display failure of one kind of phenomenon, liquid crystal display machine no power is display power on no display, LCD display electricity did not show us how to repair? The pig will divide kind of case to describe a liquid crystal display live show no fault maintenance.

And displays a live show no power failure

This is a it should be said that the very simple fault, general LCD display extension in power and outside power supply two kinds, conversion of some common. No matter that kind of power supply, its structure than CRT display of power supply much more simple, delicate general is a small element, such as insurance tube, rectifier bridge, 300 v filtering capacity, power supply switch tube, power management IC, rectifier output filter capacitor diode, etc.

Second, the display live show no driver board failure

Drive plate burning insurance or is regulated chip fault occurs, a part of the machine is the switching power supply, the output power built-in two groups, one group is 5 v, for signal processing, a set of 12 v provide Pavilion DV6700 Inverter point backlight use.

1, if part of switch power supply circuit appeared fault will likely lead to two groups of power supply are not output, first check the 12 v voltage normal no, follow check 5 v voltage normal no, because a/d drive plate of MCU chip working voltage is 5 v.

2, if find can not open the machine fault, first using a multimeter to measure 5 v voltage, if there is no 5 v voltage or 5 v voltage become very low, so a may be power supply circuit input stage had a problem, that is to say the 12 v conversion to 5 v power supply part out of the question, the fault is very common, check 5 end voltage regulator block.

3, another possibility is 5 v load increased, the 5 v voltage pull very low, that is, the signal processing circuit level after a problem, a part of the circuit damage, cause load increase. The 5 v voltage pull very low, after each level regularly problems element, replace failure element, 5 v can resume normal, failure in general to solve.

4, meet 5 v voltage returns to normal is not normal boot, this kind of situation to also have a variety of reasons, on the one hand, the MCU program is flush out may cause didn't turn on, and there is a MCU itself damage, such as MCU I/o port damage, make the MCU scanning the key, meet this kind of the MCU, to find fault caused by the hardware problem is useless, even if you change the MCU also can not solve the problem, because the MCU is the need for programming and write code, in couldn't find the original factory AD drive plate replacement, we can only use general a/d drive plate replacement such as: 151 d or 161 b, etc.

LCD backlight generally work in a high-voltage, high-current state, after a few years of use, prone to dark screen or boot screen some time dark or black screen phenomenon, generally caused due to the inverter, which is also a small lamp caused mainly in the liquid crystal display of the LCD backlight. inverter failures are generally due to ignition coil leakage, breakdown caused by the switch, but the general ignition coil replacement more difficult to match, it is generally a direct replacement of the inverter, the inverter to a single lamp, dual-lamp-like, four-lamp inverter, according to the inverter lamp the number of tubes selected to replace the inverter.


Select inverter identify the following voltage pin, the foot of the main power supply, typically 12V, interconnected with insurance, based on the typical characteristics of two ground pins, generally negative, connected with a large area of ​​copper foil, three lighting switch control pin, used to control the high voltage output of the LCD inverter, generally beside ON / OFF, four, dimming pin, used to control the brightness of the inverter lighting, generally marked with the ADJ substitution inverter method Precautions.

Roles: the role of the LCD backlight to provide a uniform brightness can be adjusted.
Composition: light guide, fluorescent tubes, inverter, inverter power supply circuit.
 

1, the light guide plate: it is emitted from the light of the lamp through the physical diffuse reflection liquid crystal panel to provide a uniform backlighting.

Failures caused by the light guide plate:
               Caused by loose water ripple: because of the light guide plate.
                 Leukoplakia: the surface of the light guide plate is dirty substances, only with water can not be cleaned with alcohol.
                 Brightness fuzzy luminous rate of less than: bad environment is wet, the surface of the light guide plate mist formation.

  
2, Lamp: it is the light source of the LCD screen, the LCD screen are linear lamp, cold cathode diameter 3.6mm, 3mm, 2.6mm, 2mm, 1.8mm, 1.2mm, etc., the tube diameter 1.2mm when the highest luminous efficiency of the lamp power consumption of the notebook are generally about 2W to adapt to the AC voltage range 450 ~ ~ 1000V between.

  Lamp failure caused by:
                 Dark screen: text image information, brightness
                 Screen yellow / red: lamp caused by aging, easy to find just machines
                 Red and flashing screen or red screen go dark immediately: Lamp serious aging caused
                 Insufficient luminous efficiencies, brightness unadjustable.

         
3, Inverter: motherboard provides DC low-voltage electricity into 450 ~ ~ 1000V high voltage alternating current, so that the lamp is lit, 5V, 12V, 16V, 19V, 20V DC operating voltage of the Acer TravelMate Timeline 8371 Inverter.

Inverter working conditions:
               VCC, then fuse
               GND
               Graphics open signal (3V or 5V)
               Brightness adjustment signal (3V)

     The Inverter of substitution:
              The new inverter is to be able to put the position of the original inverter.
              The supply voltage of the new inverter and the original inverter supply voltage.

Square wave inverters are simple to implement, but the harmonic content is too high, far from being able to apply to most cases, can only be used in a handful of harmonic content less demanding situations, but since the sinusoidal pulse width modulation technique applied , inverter technology has entered a new era, especially this year with the extensive application of DSP chip, presents the trend of digital, intelligent inverter.

SPWM inverter has the following characteristics:

1) A circuit is simple, the structure of the main circuit and the square wave inverter output voltage, frequency, and phase adjustment can be achieved, but only a half-power level;

2) may be used not controllable rectifier bridge, make the system independent of the value of power factor on the grid and the inverter output voltage;

3) FM regulator tributary of the aspects of the original parameters of the dynamic response of the system has nothing to do with the speed of;

4) can be obtained very small harmonic content, in theory, harmonic distribution on both sides of the carrier.

SPWM is the abbreviation of the Sine Pulse Width Modulation, the sinusoidal pulse width modulation, it comes from the earliest communication modulation technology, the most basic principle is to use a reference wave, "modulation" wave and a frequency N times in its triangular wave comparison, it can be obtained a group of equal amplitude and pulse width in accordance with the changes in the phase, amplitude and frequency of the modulated wave and a rectangular wave, and then this waveform to control the opening of the switching tube in the OFF, the same waveforms can be obtained the high-voltage pulse. Reference wave is usually a sine wave, so this technique is usually known as the sinusoidal pulse width modulation technology, SPWM technology.

Q: What precautions required to use the LCD?

A: The following is use the LCD's Note:

1) Recommendation / wet environment at room temperature, high temperature / high humidity will affect the life of the LCD monitor.

2) the intense temperature fluctuations will affect the performance of LCD displays, especially the low temperature will affect the brightness and response time. Recommended to work in a stable, clean environment, dust can cause internal circuit Compaq Presario CQ61-411WM Inverter failure.

3) Do not spill liquids into the monitor, For cleaning, turn off the power, detergent spray on a soft cloth to gently wipe.

4) liquid crystal display glass, the move should be to avoid the collision, vibration.

5) liquid crystal display surface of the multilayer films, carved with a sharp object is strictly prohibited.

6) Do not disassemble the LCD display, be sure of professional maintenance in case of failure.

7) long fixed screen, will decline in brightness, image retention phenomenon to increase, it is recommended to use the screen saver.

8) for a long time, please do not turn off the monitor, unplug the power cord.