The normal crt monitor have a demo display when you unplug the vga cable to PC like this image below..
If the crt monitor green LED light steady and heater beam have light, the horinzontal and High Voltage supplied to tube is completely good. If you encountered this problem just focus on video section of crt monitor. But before you start... find the flyback transformer behind this they have two controls screen & focus. After you found it plugin the monitor use plastic precision or small screw philip driver for safety to high voltage at horizontal area choose screen control rotate it to clockwise direction follow this....
If the display responses or from dim to lighter 100% you have a problem to ABL find this at the bottom of horinzontal section near at flyback transformer pins trace the line of ABL for dried solder, open resistor if nothing happen find the Video IC at chroma section and replace it. follow this...
For LG & Redfox you found LM1269NA Visit this site for seaching semiconductor matches www.alldatasheet.com Good luck.
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