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TV troubleshooting

Teach you some simple TV troubleshooting:

1. TV no sound without image is usually caused by the fault of the power is disconnected, one should check the fuse, switch and a power plug has no problem.


2 there is no sound image, but the screen has a grating and arbitrary figure, which is to see the screen after the amplification of the line is good.


3 there is a horizontal line and a straight line, indicating that the vertical scanning system or horizontal deflection coil circuit is out of order, to be sent to repair.


4 images, such as the emergence of rolling up and down, mostly due to poor reception of the link, the antenna can be used to catch up with the antenna placement and change the way to solve the problem.


5 the picture appears heavy shadow, is generally due to the high-rise buildings on the cause of the electric wave reflection, should adjust the direction of the antenna, height and fine tuning knob.


6 in case of snow, clutter and accompanying noise, the position and direction of the antenna should be changed.


7 voice out of control, suddenly and suddenly small, may be out of the potentiometer.


8 brightness to the maximum, the screen is still bleak, it is likely that the life of the tube has been.


LCD TV common fault case data


The following is a summary of some of the maintenance ideas based on our daily maintenance:

The method can be used to repair a single lamp high pressure plate to a lamp test, because now the LCD panel design is generally symmetrical design, while the two sides are likely to be bad. The general machine problem is the power of a road pipe, booster pipes, step-up transformer and lamp circuit or load, and power management IC caused by load balancing protection. There are so many see the pressure plate interface line, many beginners think the change is very complex, it is actually very simple, only need 4 signals to high pressure plate: 1, 2. 3. Power supply, switch control, ON/OFF.4, adjust the brightness of ADI. First determine the positive and negative power line, a fuse is generally positive, negative pole is connected to the capacitor anode. Then determine the best way to determine the voltage, voltage of the capacitor is marked to see if. About 6V 3.3V is that, if the capacitor superscript around 12V, so the input voltage is 5V, if it is 24V or above, there is a 12V, and so on, the standard capacitor volt number by two, close to a few volts is a few volts. Some people Then according to this, it still doesn't work, or just flashed out, is a lot of pressure plate is more than this, how does that do? Find out the control at the foot, foot is receiving a small transistor on the general is directly connected to a transistor, most middle there is a small capacitor should be easy to recognize, control foot is generally 3.3V and 5V, there are also individual is grounded, so we do not know the circumstances, try not to the ground, then followed by 3.3V 5V, if the input voltage and the control voltage is 3.3V, can direct with extra feet. How to do?? let him empty well, don't ignore it.


1 monitor the whole machine without electricity


(1) power failure: This is a should be said to be very simple failure, the general LCD power supply and external power supply in the extension of the two, the machine is a common. No matter what kind of power, its power structure than the CRT display much more simple, vulnerability is usually some small components, like insurance tube,.300V bridge rectifier filter capacitor, power switch, power management IC, diode rectifier output filter capacitor, etc.. Power board commonly used ic:6841 203d06, these commonly used PMW chip in my professional LCD accessories shop can buy.


(2) driver board failure: driver board fuse or regulator chip failure, a part of the machine is the built-in switching power supply, power output of two groups, one group is 5V, for signal processing, the other group is 12V provide backlight for high pressure plate, if the switching power supply circuit malfunction will may lead to the two sets of power supply are not output. Check the 12V voltage is normal or not, follow the check 5V voltage is normal or not, because the working voltage of MCU chip A/D driver board is 5V, so the machine can not find fault when the first multimeter is used to measure the voltage of 5V, if there is no voltage or voltage becomes 5V 5V very low, then a power supply circuit input level may be a problem, that is to say 12V to switch to the 5V power supply is a problem, this failure is common, check 5 terminal voltage block (common type 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, in no way to find the original AD driver replacement plate, We can only use the generic A/D driver board replacement such as: 151D or 161B


2 the light is not bright, but the light is always bright.

This problem is generally caused by high voltage anomalies, is to protect the circuit action, in this case, the general LCD screen is displayed, look at the method is "strabismus".



3 black screen, no backlight

Strabismus LCD display image, belongs to the power supply circuit of high voltage board. Focus on examination of 12V power supply (fuse F) and switch voltage of 3V or 5V. If MCU is normal because no problem caused by the output of the switch control voltage can be directly extracted from the 3 terminal voltage block (AIC1084) instead of 3.3V. The pressure plate method (repair the power switch control tube fuse - - power management IC---- send large - power switch tube push-pull ----DA converter circuit (inductor, rectifier) ---LC converter (step-up transformer, a capacitor, capacitor - lamp tube).


4 screen bright line, bright or dark belt


This problem is generally a liquid crystal screen failure.

Bright line fault is generally connected to the LCD screen of the main body of a problem or a row and column driver IC damage


The dark line is generally screen body leakage, or TAB connection open flexible plate. Two problems above basically is to give the machine a death sentence, no maintenance value, because a piece of screen price is too high. Guangzhou has a special replacement chip, a very high rate, repair rate is high.


5 flower screen or white screen


This problem is generally the screen driving voltage is a problem, first change the drive plate and drive line screen test, if you check the screen back power supply circuit, driving voltage board maintenance ideas: 5V 3.3V (AIC1084) is a power supply output. The screen driver board fuse (F) - 3.3V -----DC-DC conversion circuit, negative pressure the formation of IC (-7V) - row, column driver IC.


AAT1101A M150XN05 screen power management chip, the performance of the white screen after the start of the image is dim


AAT1164 M170EG01 new screen common fault, mainly used in BenQ FP71G+ LCD above. With a period of time will be white screen, shutdown in a period of time to open a white screen. The chip for the LCD screen and the production of high voltage chip management, BenQ LCD monitor often bad, fault: white screen.


AAT1343 LG, PHILIPS boot screen, white screen, bars etc.


AD8567's screen with a white screen.


The AU30707's screen, white screen, light image


The AU30803's screen, white screen, light image


AUO-003 M170EG01 screen, the main power supply circuit, the boot screen or boot screen, white color distortion, color bars etc.




FPD87326 LG PHILIPS screen IC






LPD91821 Samsung LCD screen dedicated


LRE031212A LTM170EU-L21 main chip on the screen












MST8116B CMV BENQ and so on, the LCD display main chip, this IC damage rate is high, failure: flower screen, white screen, connection signal line without display


MST8131A MST8131A MST8111B MST8111A Lenovo BENQ, GM, Acer LCD IC main chip, the high failure rate, failure: Huaping, white screen, no display signal line connection






SE7889-LF Samsung LCD driver chip IC board, the high failure rate, failure: Huaping


SN0209033PZP LG.Philips LCD screen dedicated LM170E01








More than WT61P4 of these chips can be ordered here, some of the chips may order a long period of time, if necessary, please send a text message screen model IC model to: 13938098718


6 color fault


Generally can be adjusted into the factory adjustment mode. Without this mode, maintenance ideas: replace the screen line and the adapter plate, rewrite the driver, driver board bad (not common) - screen control IC backplane bad (not common) - off screen line observation of backlight color (color flat backlight lamp aging) - for the lamp.


7 character virtual or trailing


Maintenance ideas: check the VGA signal line, the ground point of view three R.G.B line is connected properly, replacing the screen line or transfer board, driver, driver board for rewriting the ----LCD screen back signal interface IC bad -----LCD screen back contrast potentiometer ------LCD screen light guide plate dislocation -- polarizer dislocation


There is a stain on the 8.LCD screen


Maintenance ideas: wipe or replace the protective film - open the screen to clean the outer polarizer and organic glass (with cotton balls, pure water treatment) - drying


9.LCD screen leaked or uneven light


Train of thought: re install lamp tube - adjust light guide plate


10: LCD screen highlights


One or two big bright spot, can try gently with fingertips pressure highlights, can disappear, so that the pixel electrode of virtual switch and even small black and grey. There may be a point inside the light guide plate or polarizer is caused by dust. The cleaning process.


The above method to take the first customer agrees that during the trial, before the operation, otherwise the consequences themselves, all the responsibility has nothing to do with my old Kang.


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 warning "out of frequency range"


Check the signal line: Rewrite MCU driver to replace the EPROM------ EPROM program - - override change drive plate


13: does not press the switch button after the power that the white screen backlight, the image can be displayed after the button


High voltage switch board interface signal and the ADJ signal caused by the reverse connection, switch signal output part of the drive plate MCU is not normal, you can override the MCU program for MCU repair.


14: added, for the replacement lamp aging screen to find out the tube size, because although the screen size, but the tube length and thickness is slightly different, can not find the same size of the lamp, the lamp is short if it is good, if you can not use a slightly longer tube with careful removal of screen box the knife, and with good insulation heat shrinkable tube.


Common troubles and maintenance essentials of LCD

The following is the structure of a liquid crystal display and all accessories


1, PANEL (Ye Jingping) 2, A/D driver board; 3, LCD screen drive line 4, pressure plate (also known as rose plate, high pressure, 5 INVERTER), high pressure plate wire 6, power adapter (external, usually use 3A/12V DC switching power supply), also part of the built-in display in the machine part the direct input AC220V


Fault phenomenon: TV state images, sound are normal, but in the DVI state without image.


Maintenance ideas: TV state image sound are normal, and the input signal from the DVI interface without image, indicating that the I2C bus settings or internal conversion switch abnormal.


In the boot state, press the "program" button, then press "9", "7", "3", "5" and enter the I2C bus factory menu, call up the "DVICON" (digital video input interface control), whether it is in the "OFF" or "ON" in the state state. If the "OFF" state, it will be changed to "ON" state, and then from the "DVI" interface input signal, you can return to normal.


Cases of 2:


Fault phenomenon: images appear negative for a long time to work, but the sound is always normal.


Maintenance ideas: as the sound is always normal, the fault may be the image processing circuit or progressive digital frequency conversion circuit is faulty. The system adopts FLI2200, which is composed of line transformation processing, matrix transformation and fast motion compensation detection.


First check whether the image processing circuit is abnormal; if not, there is a fault in the line digital converter circuit. The FLI2200 replacement, the fault can be ruled out.


Cases of 3:


Failure phenomenon: image flicker, but the sound is normal.


Maintenance ideas: first determine the location of fault, if the TV/AV state appeared the fault, the fault line in the digital conversion circuit; if the VGA or DVI state and TV/AV state is normal, not normal, then the fault is caused by the abnormal operating mode. Then check the following methods.


In the boot state, press "program" button, then press the number "9", "7", "3", "5" key, and enter the I2C bus factory menu, select the DVI/VGA conversion, to see whether there is abnormal; without exception, the digital frequency conversion circuit (FLI2200) internal not good. After the replacement, the fault can be ruled out.


Cases of 4:

Fault phenomenon: white raster, no image, but the sound is normal.


Maintenance ideas: white screen can appear on the screen, and the sound is normal, indicating that the former signal is normal, may be the image signal input or drive circuit failure.


Check the power supply board 5 V DC voltage is normal; if not, then may be 5 V power supply connection broken or plug contact bad. First line detection along the line, if there is no exception, you can unplug the 5 V power plug, remove dirt and rust points, and repair the lead wire to make good contact, the fault can be ruled out.


Cases of 5:


Fault phenomenon: the sound is normal, but the image is dark, adjust brightness invalid.

Maintenance ideas: because the sound is normal, but the image brightness is dark, may be the backlight aging, drive circuit, digital frequency conversion, CPU control circuit of a bad. Replace the first backlight, such as fault is detected on the same circuit, if the fault can not be found, it may be a digital frequency components exist in weld, welding using a hot-air gun blow again, failure can be ruled out.

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