plasma tv picture problem

i have a philips plasma 42 hdtv the picture is great, but the past few
months i developed these broad horizontal wave bands that move vertical
up/down slowly on my sceen, i more noticeable when i put a blank sceen
on, any suggestion--i have tried shanging setting contrast/brightness
but still visible-

I use to get similar waves on my desktop lcd which only had an analog VGA
connector (no DVI). What are you watching when you see the horizontal lines
and how is that device connected to the plasma tv?
"dr63" wrote in message
oups.com...
i have a philips plasma 42 hdtv the picture is great, but the past few
months i developed these broad horizontal wave bands that move vertical
up/down slowly on my sceen, i more noticeable when i put a blank sceen
on, any suggestion--i have tried shanging setting contrast/brightness
but still visible-

This sounds like hum bars. There is a ground somewhere that is not
making contact. This could be on a video or audio cable, or even on a
power cable. Break and remake all the connections among the components
and see if the problem goes away.