TCL LCD TV logic board 37T03-C04 white screen troubleshooting - Home Appliances

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Electronic scale crystal oscillator 3.2*2.5mm 3225 16M (16.000MHZ) 12PF 10PPM 20PPM 30PPM

Brand AVX TPSE226M035R0125 Low impedance tantalum capacitor AVX 22

I recently worked on a TCL 37-inch LCD color TV that had a white screen issue, although the sound was working fine. Based on previous experience, I suspected the problem was related to the logic board. The gamma correction chip on the board is an AS15-HF model, which has 22 gamma voltage outputs and 14 operational amplifier circuits, all configured as emitter followers. The non-inverting inputs of these op-amps are connected to a low-to-high step reference voltage, which generates 14 different gamma voltage levels. After checking the key reference points on the logic board, I noticed that only the VCOM point had no voltage, while all other reference voltages were normal. This led me to suspect a faulty AS15-HF chip. I replaced it with an AS15-G chip, hoping this would fix the issue. However, after powering up the TV again, the same white screen problem persisted. That’s when I started to think deeper about the root cause. I decided to test the VCOM output pin (pin 47) of the chip. When I lifted the test lead from pin 47 to the VCOM reference point, I found the resistance to be infinite, indicating an open circuit somewhere in the trace. I checked the connections between the VCOM reference point and the two screen lines, and they tested okay. But the line from pin 47 to the VCOM reference point was indeed open. Instead of spending more time tracing the exact location of the break, I opted for a quick fix by adding a flying wire as shown in the photos. After this repair, the TV displayed a clear image without any issues. It was a bit of a hassle, but sometimes a simple workaround can save time and effort.