Skyworth LCD TV 32L05HR heat machine flower screen maintenance example - Home Appliances

Probe current voltage pin 420*4450 head diameter 5.0 over current current and voltage pin

TP-IP4220CZ6 5V 0.35PF breakdown voltage 6V SOT

Shunuo varistor / ESD varistor / product complete / Sunlord first-class agent

Photocoupler

This Skyworth 32L05HR LCD TV is a street seller from the county. It is said that it is just starting up, everything is normal, but after a period of time, it is less than ten minutes, more than an hour, and instantly becomes a flower screen. There was a big squeak in the speaker, so he let the TV go down and sent away. The boot experiment is indeed the same. After the flower screen, there is a harsh sound in the speaker. Listen carefully to the noise point when the old TV has no signal. The sound, shut down and then open again and normal, and then appeared again, the time is getting shorter and shorter. The fault is as follows

[attach]460944[/attach]
At first it was suspected that it was a plastic screen, but it was not a plastic screen through the vents. Since the sound image is not normal, the screen and the logic board should be fine. The fault should be on the power board and the digital board, but the status of the screen is like a number. Board DDR is bad, plus the sound also makes a strange sound, it should be a problem with the digital board, the power board may be fine, disassemble the machine and find that the screws are not finished, understand, this TV has been overhauled, not repaired No wonder it will drive me twenty kilometers to drive me here, but this matter is no longer important. It is the key to repairing. The whole machine and digital board are as follows.


First observe the power board and digital board, did not find the original damaged parts, check the voltage, the power board 5 volts 12 volts 24 volts normal, the digital board 5 volts 3.3 volts 1.8 volts 1.2 volts are also normal, is the DDR chip bad? But with DDR heating, the fault does not appear, heating the main chip is not good, and the maintenance is in trouble. Later, the information is found to be known as a technical change. It is also a common problem. It is to replace the 1.8-volt regulator block. The diode of the block input is further connected to a diode. The reason is that the input voltage of the voltage regulator block is too high. The time is long, the voltage regulator block is bad, and the output reaches 2.2 volts. However, the measured input voltage is 4.8 volts and the output is 1.8. Volt, the voltage before and after the fault is unchanged, but not assured, it will be changed according to the technical changes. After the change, the measured input voltage is 3.6 volts, and the output is 1.8 volts. However, less than an hour, the fault appears again.

Temporary maintenance is in trouble. After thinking carefully, I feel that I should change my mind. I can't blindly repair it. Since the heat engine is faulty, why not try it one by one? When heating to U18 with a soldering iron, the fault will appear immediately. This model is MP8708EN. There is a problem with the voltage regulator chip. After careful observation, it is found that the U18 is a 12 volt to 5 volt regulator chip. The output of 5 volts is all the way to the three-terminal regulator that I have changed. After the supply of DDR, the picture is as follows

Immediately after replacing the U18, the test machine was continuously tested for five hours. The whole machine was normal. The test was still on the test machine. The fault did not appear. The instructions have been fixed. The normal picture is as follows
[attach]460961[/attach]

PS: It should be that this voltage regulator block is bad, so the output voltage of 5 volts is increased, causing the flower screen and sound to be abnormal. This machine reminds me of a 39 Skyworth network TV repaired last year. The fault is more strange, blue screen. Normal, the remote control is normal, but regardless of any signal source, as long as it is connected to the screen, some are the whole machine line, some are half of the black screen and half of the snowflake. After being repaired for two months, it has not been repaired. Later, after pulling it here, I found it to be a 3.3 volt steady. The output of the clamp is only 2.8 volts. The output of this regulator only supplies power to the 1.8 volt regulator block of the main chip, but 1.8 volts is always normal, indicating that the block is also outputting the ripple voltage. There are a lot of ripples that interfere with the normal operation of the main chip, causing strange faults.