I recently worked on a Skyworth LCD TV model 26L08HR that had some display issues. The screen would light up, but the image was flickering with color trails. After checking, it turned out to be related to the logic board. Since the logic board and the screen COF are integrated, replacing just the logic board wasn’t an option. I tested several key voltages: VIN was 12.15V, VGH was 28.8V, VGL was -5.35V, VDC was 3.28V, and VDA was 13.3V — all of them were within normal ranges. However, when measuring the VSCM voltage, it only showed 3.5V. That’s where the problem was. VSCM is also known as VCOM, which is the internal drain voltage of the TFT in the screen.
I carefully checked the RC components in the VSCM circuit but couldn’t find any obvious faults. Then I realized that the VSCM voltage was being adjusted through a REF resistor. After tracing the circuit and cleaning the resistor with some cleaning solution, I adjusted it and saw a noticeable improvement in the image quality. It turned out the resistor wasn’t faulty, but there was poor contact due to oxidation. Once I adjusted the VSCM voltage to the correct value of 6.3V, the image became stable and colorful, and the issue was resolved.
This case shows that even complex-looking problems often have simple solutions. Sometimes, what seems like a logic board failure might actually be a voltage issue or a small component malfunction. The key is to systematically check the voltages at critical points and not jump to conclusions. I’ve learned that patience and careful analysis are essential in repair work. I hope this experience helps others who might face similar issues. Feel free to share your own experiences too — we all learn from each other!
MINI FAKRA Automotive Cable Assembly
Dongguan Zhuoyuexin Automotive Electronics Co.,Ltd , https://www.zyx-fakra.com