25NM-90004T36机芯,声音正常,光栅和图象的亮度隐约可见.开机检查:电源正常,行扫描电路正常,视放电路也正常,仔细检查发现显象管的灯丝不亮,测灯丝电压极低,测电阻R335(2W2.7欧)已增大5欧,换同值(2W2.7欧)后,故障排除.