Inspiron 9300 Video Flickering

Recently my 4yo Inspiron 9300 has begun to suffer a flickering screen problem that appears to be getting worse. Months ago it started where occasionally the screen would flicker (go black/lose picture altogether) once and then come back for a long period of time. Lately the flickering has become so bad, I don't care let someone with epilepsy view it. In the past few days, the screen has begun going black, and staying black. Rebooting it always fixes it, at least temporarily. The longer it sits, off, the longer it will take for the flickering to start again.

I run my systems hard. This particular laptop is on almost constantly, and for a good period of time, so was the screen. I run Linux on it, and the power settings didn't work all that well until recently. I simply assumed that I wore out the screen.

Last night I accepted this fate and tried plugging an external screen into the RGB port on the laptop. The external screen would simply show the exact same thing that is on the main screen, it was not it's own independent desktop. However, I quickly noticed that the flickering was also now happening on the external screen, in unison with the laptop screen itself! The problem can't be the screen itself, then. I have connected the laptop up to a screen via DVI, but in that situation, there were two separate desktops: screen 1 on the laptop, screen 2 on the DVI-connected screen. Even though the laptop screen would flicker, the DVI-connected screen did not. I have not tried connecting a screen through DVI that simply mirrors the laptop desktop as I did with the RGB connection, above.

A little other history: about a year ago my battery light on the laptop began flashing orange. The pattern typically went: green ... orange orange orange ... green, repeat. Today it seems much more random than that: green... green ... orange ... nothing ... green ... orange, etc. The system simply fails to remain powered when the battery is removed from the laptop and is running straight from the power adapter.

This system has been known to get VERY hot in the past few years. While I'm usually very good with my system maintenance, this one somehow got looked over. Clogged air vents built up over most of it's lifespan meant it was not uncommon for the CPU core temp to operated, on average, between 60-70'C, and would sometimes exceed 90'C if running video or other CPU-intensive tasks for long periods of time. I blew out the dust several months ago and the CPU temp has been VERY noticeable; it usually hovers around 30'C and rarely exceeds 50'C on high-load.

Some of the reading I've done online about similar problems with the flickering screen are usually mentioned in the same breath as a beeping power adapter. I have had no such symptom. My power adapters have not beeped at all. What I have heard is a strange squealing noise coming from the laptop itself. Nothing that could silence a room, but definitely noticeable while in a silent room. It doesn't "squeal" all the time, but when it does, it lasts several seconds (5-15) before vanishing.

My primary issue is the flickering screen, but since it doesn't appear to be the screen itself, I'm wondering if some of these other symptoms might factor in. And if they do, are they fixable? If it's a case of replacing the battery or a power adapter, that's cool. If we're looking at replacing components or soldering, then maybe not so much.

Any thoughts??