Konka color TV P21TK828 three trouble-free maintenance - Home Appliances

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Fault model: Konka color TV P21TK828
Fault phenomenon: Three trouble-free maintenance steps were taken. First, visually checked the fuse and found it intact. Then measured the main filter capacitor and B+ voltage, which showed no short circuit. The main power input was 300V, and B+ voltage was 48V, but the power indicator still didn’t light up. Further testing of the optocoupler showed that pins 1 and 2 had only 1V, suggesting it was functioning, but the B+ voltage was low, so the power supply might not be the issue. Since the indicator wasn't working, it was suspected that the CPU power supply was abnormal.

The first step was to measure the 8th pin of the memory chip, which showed 0.5V. After power-off, there was no short to ground on the 8th pin. A back-test of the switching power supply revealed a 6V output from the CPU power supply group. While examining the N952 chip under a magnifying glass, a fault was identified at the 8th pin. After repairing the issue, the optocoupler was restored, and the TV returned to normal operation.

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