Changhong color TV PF2139 one machine diseased fault repair - Home Appliances

Single chip microcomputer STM32L151CCU6
Brand AVX TPSE226M035R0125 Low impedance tantalum capacitor AVX 22
Electronic scale crystal oscillator 3.2*2.5mm 3225 16M (16.000MHZ) 12PF 10PPM 20PPM 30PPM

This morning, a customer brought in a Changhong 21-inch color TV model PF2139 that had been previously repaired at another shop nearby. The original issue was that the TV wouldn't power on. The technician there mentioned that the high-voltage board was faulty. After replacing it, the TV turned on, but there was no image. The technician spent two days working on it and finally said it couldn’t be fixed, suggesting a motherboard replacement. The user refused and brought the TV to me instead. After plugging it in, I confirmed that the TV could indeed start. The main issues were: the horizontal line was shifted to the right by about 10 cm, there were several horizontal lines at the top of the screen, and sometimes the image would flicker. I quoted 80 yuan for the repair, and the user agreed. Upon disassembling the TV, I found that the new high-voltage board had already been replaced, and many components in the field block had also been changed. There were signs of rework and possible cold solder joints. However, the boot failure remained unresolved. Instead of immediately replacing parts, I started by measuring the voltage at the field block. The field IC was TDA8356, and I checked pin 6, which should normally be around 45V. But I only measured 16V. I traced the problem back and found that the high-voltage rectification output was normal at 45V. Then I noticed a 10-ohm resistor, R404, connected to pin 6. It had failed and was open. Replacing it fixed the retrace line issue. Next, I focused on the center line deviation. I suspected a horizontal pulse issue. After careful inspection, I discovered that the copper trace on pin 6 of the high-voltage board was broken, specifically near the rivet. This was a very subtle defect that was hard to spot. After re-soldering the area, the center line returned to normal. However, the image appeared slightly too large, which made me think the high-voltage output might be insufficient. I adjusted the reverse capacitance slightly, and the image was fully restored to its correct size and stability. [attach]453516[/attach] [attach]453517[/attach] [attach]453520[/attach] [attach]453521[/attach]

Wire To Board Connector

Wire To Board Connector,0.6Mm Wire To Board Connector,1.25Mm Wire To Board Connector,1.5Mm Wire To Board Connector

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