Today, I received a 42-inch "SAMSUNG" plasma TV, model: HP One 4254. When I turned it on, the only sound I heard was the power board relay making a continuous "click-click-click" noise, repeating over and over. This kind of behavior is quite concerning because it indicates a wide range of potential issues—every part of the machine could be involved, so there wasn't an immediate clear diagnosis.
To be safe, I decided to perform a conservative inspection. I checked voltages like 5VsB, 5.3V, and 12V while listening to the relay's sound, but neither Vs nor Va were outputting any voltage. From this, I concluded that the power board was definitely faulty. To double-check, I disconnected the power board and tested it separately. The result was the same—still no power.
At this point, I had no choice but to go deeper. I started testing components one by one on the power board. During my checks, I made a surprising discovery: one of the field-effect transistors, QX801, which is a 11N50CF model, was completely shorted out—reading 0 ohms. That was the key clue!
I replaced the defective transistor with a similar one and inspected the rest of the components for any other issues. After confirming everything else was in order, I reconnected the power board and powered on the TV again. It worked! The relay no longer made that annoying clicking sound, and the system was stable.
The repair cost was around $268. I sent the photos to the team for confirmation. Thank you all for your support!
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