I've had my 1 GHz titanium PowerBook from new, about a decade ago and it's been very reliable. A couple years ago I got a cheap generic main battery from China. Never stellar, over the last few months battery life has really diminished and I'd get a total out of power shutdown (no sleep) at 85% charge. So I ordered a new battery, which hasn't arrived yet.
But yesterday I found the machine would not power on at all (Superdrive spins twice, hard drive spins, fans come on and stay on, screen stays totally black/unlit, no startup sounds at all).
There have been no hardware or software changes for years. I found that Control-Cmnd-Power combo (I think, I tried so many), worked once and then I backed everything up. I then did your PRAM disconnect/reconnect trick and it worked, but when I put the main battery back in, the machine would stop booting again. I then tried your trick while running with a constant wall connection, without the main battery and that worked, but each time I put the case back I'd again lose the ability to boot. I then tried without the PRAM battery at all, and that worked, until I put the case back on the machine would not restart again. Having done that a couple times, I couldn't get it to start at all, even with the case off.
I left it plugged into the mains with no PRAM or main battery for one last go and got a good startup chime, but no screen and all the other symptoms the same.
Each time I reset using the logic board button to the top right under the key board. Sadly I don't have an Apple power adapter to check the orange-green light. I have ordered a PRAM battery.
What else can I try/is likely to be the problem?
Should the machine be able to run properly without a PRAM battery? If it can't does that indicate something else is wrong? Is the main battery a distraction/irrelevance to troubleshooting?
I'm sorry if this rambles but I wanted to cover everything and really want this old machine to pull through... Thank you for a great site,