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分析检修:开机满屏红光栅、查红枪视放管V505基极、发射极电压正常,但集电极电压为90V,明显偏低。本机视放板还有两个字符激励管,断开红色字符激励后为正常黑白光栅,沿线查至V302(2SC1815)b极电压为0.5V,而N601(M50436—560SP)的(47)脚为正常的0.01V。V302的bc结并有一个瓷片电容C344,拆开该电容检查,发现漏电(正反向电阻均为12kΩ)。这样,此电容便成了V302的偏置电阻,使V302饱和导通,使红枪阴极电压下降,导致满屏红光栅,换下C344(39PF)后,故障排除。
Analysis and maintenance: boot screen full of red grating, check the red gun as the tube V505 base, the emitter voltage is normal, but the collector voltage is 90V, significantly lower. There are two character excitation tubes in the local video board. After the red character is turned off, the normal black and white grating is activated. The voltage of the B pole is 0.5V along the line and the voltage of the N601 (M50436-560SP) pin (47) 0.01V for normal. V302’s bc junction and a ceramic capacitor C344, open the capacitor check and found leakage (positive and negative resistance are 12kΩ). In this way, this capacitor has become a V302 bias resistor, V302 saturated turn-on, the red gun cathode voltage drop, resulting in full screen red grating, replace the C344 (39PF), troubleshooting.