[adautolouren]

I had a powerbook G4 667MHz. Several years ago, after a presentation (I don't remember which projector was used), my mac presented the following symptoms, after I tried to turn it on:
1. press the start up button
2. chimes came on
3. hard disk started to spin and suddenly stopped
4. only the CapsLock or NumLock keys leds were on
5. no video (screen was black)
6. no sign of "life" at all
7. I had to hold the power button for about 10 seconds for the CapsLock and NumLocks keys leds to turn off.
(Note: the battery charged normally, even not being able to turn the computer on.)

After trying all the possible "repair" suggestions (without success), for several weeks, I replaced the mother board.
Everything was back to normal...
Until about a year later! After another presentation (again, I don't remember which projector was used), my powerbook presented the same symptoms.
For few weeks, after both incidents, the computer sometimes turnned on after I reseted the PRAM and used Opt key + Command key combination...

I replaced the computer... I have been using a powerbook G4 1GHz since then.
About a month ago, the very same thing happen to it.
In the case of the G4 1GHz, the symptoms have been the same, except that I can still turn it on by by resetting the PRAM several times and holding and pressing several times the Opt key. Up to now it had come back alive, and when it is on, it works normally.

Do anybody have a clue of what could be the problem?
Both computers started having the same problem after being used with a projector...

I'll be replacing my Powerbook soon, but I would like to see if I can still get something out of it...
Or at least find out what is causing the problem...
It is more a matter of curiosity, to see if there is indeed a hardware design flaw...

Thanks

[shifuimam]

What happens when you plug the machine into a monitor/projector while the computer appears to be dead? It sounds like it's booting, but isn't properly displaying video on the internal display.

If you look closely (or shine a flashlight on the LCD), do you see an image? That would indicate that the backlight is failing...

[Waragainstsleep]

Those are not common symptoms for titanium PowerBooks. iBooks maybe, but not PowerBooks.

When you say PRAM reset, are we talking Command-Option-P-R? Or did you use the reset switch on the back?

My only initial guess is the video card was having a tough time but this seems a bit strange to me. They very rarely failed on these units. How old was the 667 before it started playing up? Could it be the clock battery? That can cause all sorts of weirdness.