A few days ago, a 70-year-old user brought a Sony 46-inch LCD TV KDL-46CX520, green flower screen failure (there are photos below); just do not take a closer look at the boot, the performance of the longer time is more obvious. I feel that it is not easy to handle, leaving the phone to let the user down and disagree! Don't let the dismantling at that time rush to watch TV! Unpacking the processing cable does not solve the problem, and the motherboard voltage is not found abnormal! Just the wife let the old talents agree to let go of the repair.
After eating dinner, calm down and analyze the fault should be on the logic board motherboard or screen, the logic board is the most suspect! I remembered that the local maintenance group (more than 40 local maintenance technicians WeChat group) had said that I was repairing an identical TV. I called the TV still and asked him to go to the maintenance department to open his logic board. Street less than 1 km away)! Take back the same machine failure phenomenon! Look at the table at 9 o'clock in the evening and then trouble others is not suitable, sleep! Say the next day!
The old man has not eaten breakfast the next day! This is too anxious! Give him the afternoon to give the results (already arranged in the morning)! At noon, the brother called and said that his motherboard has been returned to the TV for repair, and it will be handed over to the user. His TV is backlit and the screen is dark blue, no image and no characters, and the motherboard supplies the logic board with 12V. Normally, after lunch, take the motherboard and cable to the test machine. After the test, it is determined to be the motherboard problem! Just came back, the old man is already waiting for me, asking me to find the problem! See him so eager to quote directly! After some bargaining, I decided to change the board and took a motherboard to put the TV on the side!
It stands to reason that this TV is waiting for the change board to collect the money! Very simple! But it is counterproductive! After waiting for a few days, the board finally came back. The motherboard was loaded with the test machine. The video sound was normal and the picture was achromatic! The menu color is normal, so that the system does not let the user take the remote control (the button can not adjust the system setting menu), after entering the menu, the system settings are normal, and the factory settings are not restored! Finally, after contacting the seller, I took another motherboard!
Waited for another 5 days! The image will not come out after the board is installed! The menu shows normal sound without images, junk seller! After contacting the seller, let me call the repairman the next day, and let my board do not repair his bad board! At night, when looking at the motherboard, the fault should be between the BGA main chip itself and the peripheral edge of the chip to the motherboard output cable interface! BGA can't move at random, take out the digital watch and try your luck outside! In less than two minutes, it is found that the resistance of a row becomes larger! The 8-foot 1.5 ohm resistance meter is slightly larger than the sesame seed. The 3 groups are 2 ohms normal, and the other two feet are more than 200 ohms! Looking for the board in the hand does not have the same resistance, I wanted to solder a small chip resistor on the original resistor, but the original resistor is too small to work; I have to try the pull line first, and then connect a 1.5 ohm resistor to the normal image! The fault under the welding is established, and it is determined that it is caused by the resistance! The next day, ask the master for help. Go to him and remove a row of solder mask on the bad board. Come back and test the machine for a long time and hand it to the user!
The motherboard has a high failure rate, and the cable interface on the motherboard is very garbage-free! The same motherboard interface is not exactly the same! If the cable is pulled up several times, the positioning point on the cable will be rotten. If the cable is not positioned, it is easy to be misplaced and cause protection! If you do not connect the cable logic board or the cable is not plugged in well, it will cause the TV red light to be on and not on! So that after the plug on the motherboard is plugged in, I dare not pull down! Pull out the cable interface on one side of the logic board to avoid damage to the cable!
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