In the morning, I received a 21-inch LG color TV. The owner mentioned that he smelled something burning last night and then saw smoke coming out. Upon inspection, I found two resistors in series on the ABL circuit had burned black. This is an over-voltage detection issue, and the burned resistors likely indicate a local short circuit. Further checking revealed that Q301 was damaged. These two resistors are Samsung's 22k and 51k types. After a thorough check, no other obvious faulty components were found. The screen was bright, but the AV signal image appeared slightly gray. Even when adjusting brightness and contrast to maximum, there was no layering, and the colors weren’t very vivid. The accelerating voltage didn’t seem strong either.
I wondered if there was a fault in the ABL circuit. Could it be that the 8880 block is damaged? The brightness wasn’t too low, but there were visible retrace lines. Could the CRT be aging? I reluctantly measured the tailgate voltage and found the filament voltage was only around 2.8V AC. Looking at the current limiting resistor, its surface was yellowed. When I removed it and measured, it had increased from 1 ohm (1 watt) to nearly 10 ohms. Replacing it with the original 1-ohm resistor restored the brightness of the grating. Adjusting the acceleration voltage to a moderate level resulted in a clear and vivid image. The repair was complete — just one current limiting resistor. It took me almost two hours of head-scratching and frustration, but everything worked out in the end.
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