Changhong plasma TV PT42638NHDX does not boot failure repair example - appliance repair - Database & Sql Blog Articles

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I recently had an issue with my Changhong plasma TV model PT42638NHDX. The indicator light was on, but the TV wouldn’t turn on. After opening the back cover, I checked the voltages: 12V, 5V, 3.3V, and 210V all looked normal, and the power button worked as expected. Using the elimination method, I removed the Z-board and noticed a sound during boot-up, which led me to suspect it was the problem. I ordered a new Z-board online and installed it carefully, but after booting, the issue remained the same. Upon rechecking, I found that the new Z-board was also faulty. I did some research and discovered that many users have reported the same problem. It turns out that different versions of the same model might not be interchangeable. Since I had already picked up the board in person, I didn’t want to waste time ordering again. I decided to try repairing it instead. After examining the faulty board, I found only a few FETs were damaged. Replacing them allowed the TV to power on again, and I thought the issue was resolved. However, when I connected the signal, there were occasional red dots on the screen—something common with Samsung panels. I adjusted the VRS801 from 205V to 209V and changed the VR5001 adjustable resistor on the lower left corner of the Y-board from 1k to 10k, turning it counterclockwise. This fixed the image issue completely. The user has been using the TV for over a month now, and no further problems have occurred. It was a challenging repair, but ultimately successful.