I encountered an issue with a Samsung LCD monitor that wouldn’t display anything after booting up—it had a black screen. After disassembling the unit, I examined the four-lamp interface on the high-voltage board.
Using an oscilloscope, I measured the feedback terminals of the two lamp sockets at the bottom and compared the waveforms. Both signals looked identical, which was confusing.
After replacing the upper connector, only one of the feedback signals became normal, while the other remained unstable. This indicated that there was an issue with that particular lamp.
The customer needed the monitor to work as soon as possible, so I decided to try a quick fix. I connected a capacitor labeled 3KV27J to the high-voltage port and plugged in the remaining three lamps. The screen turned on, but it kept flashing black. I checked the feedback signal again with the oscilloscope, and the two waveforms were still unbalanced.
To stabilize the system, I added another identical capacitor in parallel. This time, the screen stayed on without any black flashes. (Unfortunately, I didn’t get a chance to measure the waveform after the machine was fully operational.)
When reinstalling the unit, I had to flip the circuit board, so both capacitors were connected to the lower side.
This testing method can also be applied to LED displays. In my opinion, if the peak amplitude of the feedback signal is consistent, even using a simple conductor like a wooden stick could make it work properly.
ELCB is an acronym for Earth leakage circuit breaker, which is a device placed inside a water heater, commonly referred to as ELCB electric leakage breaker. This circuit breaker has the function of disconnecting the device from the circuit whenever an electrical leak occurs through the human body when touching the electrical parts of the device.
ELCB is to limit the incident of electric shock inside the machine, disconnecting the power when there is a problem, ensuring safety for human life as well as fire and explosion prevention.
How many types of ELCB?
ELCB is often used in both civil and industrial applications.
For the domestic electricity system, the installation problem is not difficult, but in industry, the anti-shock for workers and the prevention of electrical leakage for electrical equipment with large capacity requires a bridge. Automatic anti-shock, high-power leakage protection, and often has a much higher price.
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