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一台长虹CK53A型彩电(M11机芯)出现“三无”故障,初步检查发现电源开关管Q801(2SD850)、电源保险丝F901(T2—5A)和行输出管Q551(D951)、行供电限流电阻R816(5.6Ω/3W)均已损坏。换上新开关管和保险丝,用“假负载法”证实开关电源电路基本正常(注:检修M11机芯开关电源电路时也可以不接假负载)。用数字表检查行逆程电容正常。换上新行管,在R816位置串入1A直流电流表,开机发现行输出电流为350mA,再看荧屏已出现正常光栅。试机一个多小时,行电流一直稳定在350mA(无信号输入时),摸行管散热片微热。这似乎说明该机的故障已经排除,烧开关管和行管属偶然因素引起。
A Changhong CK53A color TV (M11 movement) appeared “three no” fault, the initial examination found that the power switch Q801 (2SD850), power fuse F901 (T2-5A) and the output line Q551 (D951), line supply current limit Resistor R816 (5.6Ω / 3W) are damaged. Replace the new switch and fuse, with the “fake load method” to confirm the basic switching power supply circuit (Note: maintenance M11 movement switching power supply circuit can not leave the load). Check with the digital table reverse circuit capacitance normal. Put in a new row of control, string in the R816 position 1A DC ammeter, found that the line output current 350mA, look at the screen has appeared normal raster. Test machine more than an hour, the line current has been stable at 350mA (no signal input), touch the tube heat sink slightly. This seems to indicate that the failure of the machine has been ruled out, switch and line control is caused by accidental factors.