Question waves (band lines): faint horizontally traveling slow waves but only on D-Sub cable (channel)

[Hard_Ware_69]

Recently, some faint horizontally travelling slow waves (band lines) appeared on the display. Built-in, on the motherboard, graphic card ATI Radeon HD 3300 (on ASUS M4A78T-E motherboard) worked find for 10 years until now.
Monitor is connected to computer by the usual (old type) D-Sub cable.

1. When another computer is connected (ten other computers tried) by same D-Sub cable, they all work fine, without waves. This means display (monitor) is good and cable is good.
2. The waves appear in any video mode, for any applications: on desktop, in Video Recording software and in captured on webcam videos. Changing frequencies, resolutions does not help.
3. But when I connect monitor (display) to another (second) video card's output, DVI, by DVI cable, the problem (waves) disappear on D-Sub cable (output, channel) even if I do NOT use the DVI channel for viewing. I still use D-Sub output (channel) to view the screen, but as long as DVI cable connects the monitor to computer, the waves disappear! In other words, if I continue to view screen on D-Sub channel (cable), but with DVI cable plugged in same card and monitor, there is no waves!
4. Also, there is no waves if I view the screen on DVI channel (cable).
5. I assume the problem could be: a) some old 10-year old capacitor which is blown up, not filtering circuit properly. I presume I should look close to the GPU chip, look for bulging (blown up) capacitor. Or, b) the DVI interface (connector) on the motherboard somehow receives interference when there is nothing attached to it (no cable) and its pins act as antenna. But this has never happened during 10 years. Attaching the DVI cable perhaps shields the DVI input (connector) from interference. I will test this and post result.
6. It appears that the problem disappears when there is a real LOAD on DVI connector of the video card, even though the monitor is not using DVI interface (only connected by cable to computer). Problem is "cured" temporarily when monitor is connected by DVI cable to this video interface, but, and problem only appears to be "cured": after DVI cable is disconnected, the bands (waves) re-appear .
7. I am also using Windows 8 video (graphics) card driver, on my Windows 10, because driver for Windows 10 is not available anymore. But I used this driver for Windows 8 since Windows 10 release (many years now) without any problems.

 

[popatim]

I've seen electronic interference do this.
Do yo have anything new or turned on that didn't used to be?

 

[Hard_Ware_69]

I've seen electronic interference do this.
Do yo have anything new or turned on that didn't used to be?

I added some more troubleshooting steps I performed, in paragraph number 6 of original post.