Weird monitor prob

My 5 yr old ProView 19 crt has assorted minor issues, including a PS failure I had repaired 3 years ago. Recently, the image periodically slowly dims over a few seconds, like turning the contrast full down and reducing the brightness. Gets medium dark, but does not disappear completely. Then, slowly returns to normal in a similar time frame. First time, I thought the room lights were dimming, then realized it was the monitor. The image does not distort or shrink, and the OSD menu settings haven't changed. The performance otherwise is excellent. It's not worth having it fixed again; the PS issue cost $100- and it was a squeaker then. Opinions? JR