[SteveJobs]

Hey everyone,

I've got a PowerBook G4 667 Mhz (That's Rev C, I think) with Combo Drive and OS X 10.4 and since yesterday, it acts strangely: Sometimes, randomly, it just switches off the backlight of the screen. The screen content itself is still visible if there's enough light in the room, but only scarcely.
Is it just getting old and should be replaced or is this a known Firmware or whatever bug?

Hope you know,
Greetings,
Steve

[B Gallagher]

Bumping this... I've recently been having the same problem. Doing a PRAM and PMU reset has had no effect, nor has booting from CD. The display will not give any backlight, then all of a sudden out of nowhere it will light back up!! Any other suggestions on what else I could try before I take it into the shop? Thanks.

[SteveJobs]

Hey,
here is what happened to me: I tried everything I could think of, but to no avail. I took it to the shop and they told me there are two possible causes: The display is malfunctioning of which the repair would be installing a new display which is expensive; or the inverter board is malfunctioning which is the control of the backlight. However, they said in that case it's mostly the display and not the inverter board. They couldn't tell by the eye, so they controled it in-depth and it was the inverter board which they replaced and now everything is ok again. It cost me 200 Euros, but it was ok money to get the whole thing running again.

The big question: Can you see the screen content with a flashlight or when there is enough light in the room or can't you? If you can't, it's not the backlihgt control.

Greetings,
Steve

[B Gallagher]

Steve,

Thanks for the reply - and good to hear you managed to get your PB fixed without it breaking the bank!

I've had some strange progress with my display - it works, sometimes. Most of the time the display is working, I just have no backlight (ie. the display looks like how it would with the backlight set to zero bars - I can still vaugly make out images on the screen).
Sometimes, for no apparently reason, the display will light back up though!! A restart or anything similar usually causes it to turn back off again.

I've tried all the usual stuff, resetting the PRAM, the PMU, and booting from CD. None of those make any change, so it's clearly a hardware fault, not a software one. And what you posted makes me think that it sounds like the inverter board, since the display is still working, just the backlight isn't!!

And although it's not ideal, I can afford around 200 euros to get it fixed!! So I'll take it down to the shop on Monday, and will get them to dianose it and give me a quote.

Thanks for your reply Steve!! Much appreciated!!

[SteveJobs]

Hi again,
it was the same in my case. There were like good and bad cycles, sometimes it worked great for days, then it was unusuable for a whole day or more. So: Bring it to the shop asap!

Secondly: The display connection can also be damaged so the backlight sometimes switches off, they told me at the shop back then. So, in some cases, the display must be replaced no matter if you see something or not. It can both be the inverter board or the connection and only a technician can find out.
I was lucky and I hope for you you are,too.
And if they tell you it can impossibly be the inverter board, go to a different shop. It's what the first shop I called told me...

Greetings,
Steve

[B Gallagher]

Thanks!! I'll take it in tomorrow - today's Sunday, so the shop's not open.