Start with a new cable and a different computer, just to rule out that the problem is not something else.
I repair monitors all the time. Normally if it goes dark and but you can see the picture with a flash light that is a bad cap on the power inverter. Very easy to fix. If the monitor goes "out of sync" or tells you there is no signal when you know there is that is normally the controller chip, easy to replace the controller board if you can get it cheap. If the monitor produces dead spots or colored lines as the result of trauma or just because that, is normally the glass panel. I have not found a way to fix that.