TCL TV black screen failure:
First of all, we analyze the definition of the black screen failure: TV line scan circuit work, high voltage generation, no grating. When we encounter this kind of faulty machine in inspection and repair, we will listen to whether there is high pressure sound at the moment of booting. Generally, we will hear a buzzing noise when starting the machine. If the TV has no anti-static coating, try the kinescope by hand. Positive, there will be electrostatic induction, hair has the feeling of being attracted. If there is high voltage, it means that the circuit has been working, and the fault is a black screen fault.
TCL TV black screen troubleshooting ideas:
Black screen failure first look at the tube after the boot tube neck position, the internal filament is light, normal can see the slight red light, if the filament is not bright, then check the output transformer output filament voltage is normal.
Our filament voltage is generally AC 6 volts, and the actual measurement is generally about 4 volts. Common faults include line output power supply pin open welding, filament supply resistance open welding or resistance increase or open circuit, and filament supply power supply line Plug in the end of the plug is not good, resulting in the filament voltage is not added to the display panel, as well as the filament lamp power supply inductance welding, but also check the CRT filament is open If the filament is light without grating, first increase the acceleration pole, to The grating appears, and if the accelerometer does not have a grating, it is necessary to measure whether the accelerating voltage is normal.
If there is no voltage, replace the accelerating electrode filter capacitor first. If there is no voltage after the replacement, connect the accelerating electrode wire to measure if there is voltage. If there is voltage, most of the image tube is damaged.
No grating caused by abnormal beam detection: The phenomenon is that there is no grating in the lamp. At this time, if the remote controller is pressed, the instructions received by the TV can be executed. If the standby button is pressed, the TV enters the standby state, indicating the CPU of the TV. Normal operation, this failure generally occurs in the final stage of the video playback circuit, such as the end of the video transistor triode open or damaged, then easier to determine which gun is damaged.
The method is to turn off the power of the grating after turning on the power for a minute or so. At this time, it is generally color cast. If it is a yellow grating, then the blue end-level video playback circuit is damaged. Generally, our television sets use a blue background. Early disc players also used a blue background, so the damage rate of the blue-end video transistor was high. If cyan appears, it is a problem with the red end-level playback circuitry. If there is a purple color, it is the fault of the green final-level video playback circuit.
Here are a few simple examples:
Model: 2515DZ
Fault phenomenon: The light does not turn on after the flash, after adjusting the acceleration pole there is a white raster retrace line, no character, no image, press the remote control and the machine keys do not work, or the light flashes.
Failure Analysis: Because pressing the remote control and the keys do not work, so first suspect that the CPU circuit will work abnormally after booting.
Maintenance: The voltage of the clock line SCL and the data line SDA is first detected, and the voltage is 5.1V both when the command is executed and when the command is not executed, which is equal to the supply voltage of the memory. Therefore, judging that the bus is working abnormally, and using an oscilloscope to measure the clock line SCL and the data line SDA without waveforms, the oscilloscope is used to measure the line and field pulse input terminals of the CPU, and it is found that the amplitude of the line pulse waveform is extremely small, and the step-by-step detection results in Copper foil broken.
Treatment method: After the copper foil is disconnected with a wire, everything is normal.
Model: HID29166P
Symptom: TV has high voltage, no grating.
Fault analysis: The picture tube is under normal high voltage, the filament is bright, and there is no grating. It should be the end of the visual amplifier or the acceleration pole circuit failure.
Maintenance: The acceleration voltage was measured first and no abnormalities were found. Detecting the voltage of pin 1 of the final-stage visual amplifier IC TDA6111Q, it was found to be much higher than the normal voltage of 2.9 volts, and the measured value was 11.6 volts. When the TDA6111Q pin 1 was higher than 5 volts, it was in a protected state. The Q532 has been saturated and turned on, so it is suspected that the R534 is bad, and the welding measurement has become infinite.
Treatment method: After replacing the R534 220K1/2W resistor, everything is normal.
Model: AT2965U
Symptom: TV has high voltage, no grating.
Fault analysis: The picture tube is under normal high voltage, the filament is bright, and there is no grating. It should belong to the end of the visual amplifier or the accelerator circuit fault.
Maintenance: The acceleration voltage was measured first and no abnormalities were found. After the replacement of the tailgate, the fault persists. After the suspected beam flow detection failure, no abnormal components are detected after the test.
Treatment method: Try to change R232 10KOM resistor to 4.7KOM resistor and everything is normal.
Because TVs work live and there are many lines inside, so friends who are not familiar with professional knowledge should not chaos maintenance, you can find a professional maintenance company home inspection and maintenance.
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