"Component-level maintenance first season - LCD TV repair case highlights" - Home Appliances

This is a 19-inch TCL, and the customer reflects it!

There are many reasons for no image, high voltage board, logic board, motherboard, screen are possible, the boot sound is normal, indicating that the CPU boot is no problem! The disassemble detection is correct, and the high-voltage board is not working when the power is turned on. By the way, I will briefly explain the method that I often use to measure the high-voltage board! 1Measure whether the power supply of the high voltage board is normal; 2Measure the open level of the high voltage board Stb (compared with the common high level, low level, and some opposite, as if I am repairing the 19 inch TCL); 3 or more points All are normal, the multimeter is hit to the 10V AC file, one hand holds one of the multimeter's pen heads, and the other is placed on the high voltage transformer.

If the hands will swing, it means that the transformer has been working. If it does not swing, it may be protected for some reasons. The aging of the lamp, cracking, electric leakage, protection circuit failure, etc. will cause the high voltage board not to work!

Find the high voltage board Stb port, the power measurement has been turned off

How do I know that the high level is turning off the backlight? Because the red light will turn green when the power button is pressed, the power supply is normal after the power is turned on. The flashlight can be seen on the screen according to the screen. More importantly, the STB port of the high voltage board is still in the boot or standby mode. High level, can't switch, the backlight board doesn't work! Further narrowing the scope of the fault, you can be sure that the problem is on the motherboard!

Searching along the StB port, there is a 472 resistor connected in series to 12V, which is why this port has a high level close to 9V, then this voltage must have a tube control to pull it low, yes... it is ......

This is also a normal NPN triode, the general patch can be replaced, the power is not big, through the CPU control base to achieve high-voltage board low level, power measurement BE voltage 0V, press the power button to become 0.8V However, the collector-to-ground voltage remains unchanged. The only possibility is that the patch transistor has lost its amplification capability. The 10K gear is used to measure the CE without leakage. The resistance between the BC and the BE is close to balance and there is no leakage. God The analysis of this tube from the data is completely okay. Once the fox tail is added, it will not be magnified. The first time I encountered it, I was shocked by this class!



Summary: Although this failure is the first time I encountered it, but I believe that I understand the principle, be good at adapting, and make more analysis and comparison. There will always be a solution!
Final charge red black brown


Chuangjia LCD32HD30, power red light can not be turned on! I also saw this brand for the first time, and I also used Sino-foreign joint ventures, but I can really say that I can work!



Before the demolition, everyone thought that the power supply capacitor was pregnant, and I really think so! ! Disassemble and directly scan the power supply... The result... very embarrassing, did not find the premature peach ! No way, only step by step! When the red light is on, press the power button to change the color, and there is no power-on signal sent to the power board. The remote control sound that comes out together is strange. It is awkward... There is a problem with the motherboard. ? Measuring 5V, 3.3V normal, hand touch crystal power red light does not light, power off and then open for a few minutes CPU is also hot, indicating that the CPU has been working! The remote control receiving voltage swing is also normal, and the memory supply is normal! Quietly carefully analyze... The indicator light will not switch, it proves that there is no power-on signal sent to the CPU or the CPU itself is faulty... Is it... sure, the voltage of the power-on button is close to 1.4V, normally there are more than 3V, there is no high or low level. Switch, how do you call it, no wonder you can't open the machine! Look at the circuit again, the power button and other key control circuits do not occupy the edge, but close to the remote control reception, no wonder the remote control does not respond! Replace the power button to solve the problem!

Final charge yellow black brown






An electrician in a factory carried two Changhong LT26518 and repaired it!


According to the electrician: one boot white screen, one boot full screen noise, the brightness is very low and the background process gray state, the high-voltage power supply integrated board, the motherboard and the cable received from the screen have been replaced, the fault can not be solved! Now the electrician will change the board to the super level, and some have only one certificate. ! It seems that these two things are not the cartilage head, the rest is the screen, the logic board, this is also good, save a lot of things, at least reduce the scope of the fault!

This kind of machine screen is integrated with the logic board, and the logic board cannot be replaced separately.


If you can change, these two treasures will not fall on my hand... Ha ha... This machine logic board will not work, it will be white screen, pay attention!


Maybe there is a problem with some parts of the logic board. If you feel this simple point, just take it and start it! Take the screen apart, this machine is really tearing down people, ghosts are so troublesome, the motherboard is also loaded outside the shell, and has to be removed separately to test the machine! It’s hard to open it, be careful, don’t tremble when you remove the logic board, and you’re excited to turn the screen off! Seeing no, this part is small enough, although I am a little nearsighted, I am close to junior high school, I have never worn glasses, so my eyesight has not been greatly attenuated, but close combat is my strength. !

Power-on measurement logic board 12V is normal, 14.5V is stable, 5V is not a problem, when measuring 3.3V, the problem comes, only 1.7 V, the problem is definitely here. Whether there is a problem with the load or the power supply itself is still pending verification! Measuring 3.3V regulator IC output to ground forward resistance of 5.8 ohms, measuring to scare a sweat at this time, not so black, the screen has problems ? Or is the driver IC hanging? Obvious resistance is small! Step by step, finally determine the problem is that a patch capacitor to the screen power supply leakage, installed a 103 to solve the problem!


The other screen is dark gray, and the phenomenon of noise is like the VGH power supply abnormality on the logic board. The VGL of the teardown detection is -8V normal, VGH is 2.2V, and the VGH voltage is low. Normally it should be Around 23V!

The power failure measurement VGH circuit forward resistance is 235K, which proves that the internal resistance is not low, but the power supply itself is faulty. It comes along the VGH circuit, all three panels, and there are circuits in the middle. I don’t have a haystack in the haystack, I know that you are waiting for me. !

This resistor is a 82 ohm fuse


The measurement has been increased to more than 150 K, and a 101 on the old board is installed with a power-on fault, and the VGH voltage is 23V!

Orange black brown per charge

Konka LED32HSOS! !


A common problem without power, insurance, switch tube intact, secondary no voltage output! Mostly the power IC is damaged, model 6575, can be replaced directly!


Also pay attention to the secondary power supply RB914 current limiting resistor, rectifier and 50V 47u capacitor! Charge orange green brown









Skyworth 32L16HR

The customer reflects that the boot has to look at its mood I’m happy for a few hours, I’m annoyed, I’m not responding for a long time, now I’m not booting! I heard this... I was happy to tear down the machine and scan it. This can be a good thing for me. I saw a few pregnant women. I’m on the speed, I’m going to go last night. ... Remove the measurement, although some did not rise, but the measured capacity has dropped by half!


What is it? ? You want to be Luo, you will have a dead chicken. ! Install it for a few seconds to protect standby! It’s strange... in theory, this is the right thing...



This can be adjusted, don't worry, don't worry! This is an urgent matter! Let me calculate for you...

The guys are crazy and mad, 5V, 3.3V are normal, the Stb is always on standby, the main power supply is not working, the high voltage board, the logic board are not powered, let alone the protection, now really myrrh Can be fried! Hand touch CPU is also hot, indicating that there is electricity to work, the air duct heating also bite it! Full of brains are question marks, slowly calm down, the brain repeatedly analyzes all the data collected, difficult to boot should be the ghost of the capacitor, now the boot light flashes a few times to protect, the indicator will flash to indicate that the CPU has boot The trend, what are the boot conditions missing? ? ? The brain flashed, ignoring a very important point - the data! How can I be confused at this time, immediately test the voltage of each pin of the program memory (the program memory and the user memory are essentially different, don't make a mistake! Like the MX25L1605, these include the chip select terminal CS, data output SO, protection port WP, data input SI, clock input SCK, and each port is connected to the CPU is the program memory), mainly any one of the groups of abnormalities, will cause the CPU to not boot or boot immediately protect the phenomenon! 1 pin selection terminal 1.2V, 2 pin output terminal 3.2V, 3 pin WP protection terminal 3V, 4 pin grounding, 5 pin data input 3.2V, 6 pin clock terminal 3.2V, 7 pin NC empty pin, 8 pin power supply 3.3V ! I am surprised, the data pin has no voltage swing, it proves that the cooperation agreement between the memory and the CPU is not agreed, and the low voltage of the 1 pin is definitely not normal, and the high level of the 3 pin indicates that it is in the protection state, like this Memory, the data pin must have a pull-up resistor of about 4.7K to the VCC power supply pin, remove the memory to find the route, just thought that the via hole is bad, the result is that the road is open here, never imagined, No mold and no dampness, here is a broken road, after welding with copper wire, put it back into the memory, power on 1 foot to restore to 2.5~3.3V swing, backlight start, blue screen appears, access signal picture sounds normal!


Mosaic phenomenon occurs irregularly during the test machine, and the repair welding CPU is perfectly solved!






After installing the back cover, I stretched out and unconsciously looked at the time... It was three o'clock in the morning, and I should wash and sleep! Final charge yellow black brown



These very small faults seem to be very simple. Who knows how many days and nights will be paid? As someone said, one minute on the stage, ten years of work, I am not running out of the fairy belly. It’s even more impossible to be able to climb the TV on the TV. All the techniques I hold are made of sweat. I rely on the spirit of hard work and hard work. As long as you Willing to work hard, willing to fight hard, success will not be far away from you! It doesn't matter if you fail, you can come back, but you told me to give up, I can't do it. Every successful person from ancient times to today can't do without it! Although I have achieved nothing in my studies, I believe that I can go further on the road of home peacekeeping. The key is to have a sincere reply! Are you back?