Monitor is garbled

Hello, I have a Sylvania flat screen monitor. During certain times the screen becomes very garbled. It only a minor "wavyness", but it makes viewing the screen very annoying. Also, when I turn off the computer, the monitor shows a white screen and does not turn completely off. Does anyone have any ideas? Thanks for all you help! analysisneeded

Well, used to, you could plug the monitor into the back of the tower's power supply. Which, when the power is turned off to computer, the monitor would also go off as the power to it would be cut as well. It sounds to me as if the monitor may be on its last leg… how old is it? Also you might check for anything close by that may be causing interference…like florescent lighting directly above monitor…or wireless phone/cellphone maybe..etc.