Lg Monitor goes black

Monitor goes black on start up after two seconds - screen remains black until turning unit on and off -- then back to black -- have reduced resolution to min. but screen continues to go black. Self-test not completed yet.. Replacement of cords and cables not completed yet. Power to monitors power remains but no screen light. In the past reducing the screen resolution did the job.. the monitor has been unplugged for the past two months without power. The issue has been occurring for the past two years. Now the screen will not hold the light. Have been considering it may be the LG inverter or the caps but wondering if it better to buy another monitor.