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一台日立 CTP2005型彩电,图像上部有5～6条细横线。查场振荡、场消隐电路都正常。继续检查场输出电路:实测场输出块μPC1378的第⑥脚(供电端)为24V,其它各脚电压基本正常。查电容 C_(689)、C_(686)、C_(685)均良好。换升压电容 C_(682)(100μ/50V)和升压二极管 D_(681)后,故障依旧。怀疑是μPC1378自向身损坏,换上新品μPC1378后,仍不能排除故障。
A Hitachi CTP2005 color TV, the upper part of the image has 5 to 6 thin horizontal lines. Check the oscillation, field blanking circuits are normal. Continue to check the field output circuit: the measured field output block μPC1378 pin ⑥ (power supply side) is 24V, the other pin voltage is normal. Check the capacitance C_ (689), C_ (686), C_ (685) are good. Change the boost capacitor C_ (682) (100μ / 50V) and the boost diode D_ (681), the fault still. Suspected to be μPC1378 from the body damage, put on the new μPC1378, still can not rule out the malfunction.