Video Whine

Old G/L 824 whines

Hi all, I’m what you’d call a lurker. been reading this forum for years. Great advice to be had here and I need some now.
My problem is that I’m getting a high pitched whine on all channels of the old GL 824 ( Iknow I should suck it up and by something newer but…) The noise goes away when I turn off the monitors. The noise floor is about -64db when it used to be -85db or so. This just started a few days ago when I installed a new video card and memory. I have reverted to the old card ( a Matrox 450) and the whine is still there. I even put the old memory back in. Same thing. I’m thinking shielding but which the video or the Gl. Oh and there is a Sb live in the comp too and it does not whine. this noise is evident in the ntracks meters even with the mixer and audio off.
Any advice will be of great help.