LCD Monitor Appears to Flicker

I have an HP LCD Monitor that aapears to be flickering. That is the image dims sparatically, as if you were using the dimmer adjustments on a laptop, but then it comes back up to full brightness. I’ve also had to turn the contrast down on this monitor to about 15 to be able to read the text, otherwise normal text shows as a very light grey. I wouldn’t think that the a back lights are going out but I’m not sure. It was a replacement sent by HP for another monitor that broke, and I believe it is a refurb… It reports 5419 hours…