Quickly judge the damage caused by the damage of the liquid crystal tube after the black screen - android - Phones Developers

Manufacturers supply LED lamp bead SMD LED 0805 yellow light super bright indicator light dedicated

Crystal oscillator

A Samsung LCD monitor, black screen after booting up.
Disassemble the machine and look at the four-lamp interface of the high-voltage board.


The oscilloscope measures the feedback terminals of the two lamp sockets at the lower end, and compares the waveforms. The two feedback signal waveforms are the same.




After changing the upper jack, only one feedback signal is normal, and the other feedback signal is far away. It is determined that there is a problem with this tube.



The customer is eager to use, I have to choose to go to a lamp repair method, connect a capacitor labeled 3KV27J on this high voltage port, plug in the other three lights to turn on the screen, the screen is still flashing black, the oscilloscope measures the feedback signal, two waveforms Still unbalanced,




In parallel, an identical capacitor is connected in parallel, and the screen is no longer black. (Unfortunately, the waveform is not measured after the machine is turned on).

When installing the machine, the circuit board needs to be flipped and installed, so the two capacitors are connected to the lower end.








This test method is equally applicable to LED displays.
I think, as long as the peak amplitude of the feedback detection signal waveform is the same, even if a wooden stick is connected, it will still work normally.