I'm very interested in this topic, since my PowerBook 100 suffers the exact same issue. I've talked about that PowerBook in this thread about my website (still under construction) pomme-s.ch which is (actually was) served up my the 100.

That PowerBook had been up and running 24/7 from february to november, without an issue, online and serving up the website. I had to reboot it twice after a crash. Then about two weeks ago I shut it down to move it and take some pics for the site. And boom, no way to turn it back on. Well, it boots just fine (chime, spinning hard disk and system booting), with no display. Just as you describes it, the backlighting is on but all pixels stay black.

I haven't recapped anything yet, but I did switch displays with a dead 100 I had around for the parts, and the exact same result. So I guess the issue is on the logic board rather than on the LCD?

I was thinking the issue may be related somehow to power, since my PowerBook wouldn't have enough juice to boot on its original power adapter. It would light the screen, but couldn't get a chime nor anything. It was just fine with the beefier 1xx adapter.

Now the website is runned by a 145, as the 100 is waiting for a fix...