Common fault symptoms

I'd like to think I'm getting good at troubleshooting VCS consoles. There are a few things I've managed to identify just by looking at the screen. A couple of times when I got a black image with white dots on on channel 2 and a weird flowing pattern on channel 3, I had a bad RIOT. Odd colors with otherwise crisp graphics have indicated a bad TIA a couple of time. Lack of paddle response indicated a fault on the RIOT once, but it was due to cold soldering.

What are the common symptoms of things like a bad voltage regulator, bad TIA, etc? I'm especially curious to know what kind of symptoms a bad CPU will generate.