Capacitor aging probably. They're passive components used for filtering and function based on a time constant. It's taking time for the noise to show up and grows worse. The time constants have changed from heat and component aging so the filter performs worse. The LVDS signal to the TFT panel is not going in clean if a pattern of pixels are not correct. If it were a loose or broken cable it would be instant and consistent. So it could be you need to replace the electrolytic caps near the power supply portion of the monitor. That's my guess.

On the practicality side, nice LED (backlit) monitors consume about half of the power and only cost about $80 now for a new decent model. Some out there still do have VGA inputs as well. Depends what your time is worth, I mean, this is not an HP DreamColor or anything.

Auzner wrote:

Capacitor aging probably. They're passive components used for filtering and function based on a time constant. It's taking time for the noise to show up and grows worse. The time constants have changed from heat and component aging so the filter performs worse. The LVDS signal to the TFT panel is not going in clean if a pattern of pixels are not correct. If it were a loose or broken cable it would be instant and consistent. So it could be you need to replace the electrolytic caps near the power supply portion of the monitor. That's my guess.

On the practicality side, nice LED (backlit) monitors consume about half of the power and only cost about $80 now for a new decent model. Some out there still do have VGA inputs as well. Depends what your time is worth, I mean, this is not an HP DreamColor or anything.

I have a handful of decent LED monitors with VGA inputs, but they're all 16:9 ratio, whereas my Hyundai is 4:3 -- something I want to keep for my 90s through mid-2000s rigs. It's not a necessity mind you, but I don't have any LED monitors as tall as the Hyundai, or with the adjustable stand it has.

That said, I'd definitely be willing to work on a capacitor. I had heard elsewhere that a failure like this on an LCD monitor was unlikely to be due to a capacitor (just browsing around online), but I still wondered since it seemed to be a heat-based issue. I'll take it apart sometime soon and see if I can find any bulging caps.

Actually, it's a 5:4 monitor, taller than 4:3. 17 and 19" monitors were all that. A 23" 16:9 is about the same height as a 17" 5:4. A 24" 16:9 will be about the height of a 19".
Adjustable stands are still made, but on higher tiered models. There's always after market so long the monitor has a VESA mount.

Took the monitor apart and dug down to the power inverter board: found no bulging caps. Checked each one, they read appropriately, but decided to replace them all anyway. No issues there.

Just finished a two-hour stress-test of the monitor at its native res playing a DVD off a WinXP machine over VGA, and unfortunately the artifacts still returned. This is the longest I've run the monitor in years, and there appears to be a new issue once warm: every few minutes, XP will make the new device notification sound. If you keep the display settings open when the sound goes off, it will switch from a PnP monitor driver to Default Monitor, and the available resolutions will change from those native to the monitor to universal selections. It's as if it's losing sync with the monitor, but the display doesn't go on or off. Wiggling the VGA cord and the monitor's frame don't seem to have any impact.

At this point, I'm thinking a chip inside is overheating and causing these issues. Would I be right in thinking as much? Is there anything else I could do or check?

Bump to see if anyone has any ideas. Will probably scrap the monitor if nothing turns up. It served a good life during my teens anyway. 😀