Powerbook G4 17" aluminum; screen goes black when opened more than 60 degrees.

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As the subject line says, my 17" aluminum Powerbook G4 is having some display problems. The backlight works when the laptop is opened less than fully, but once fully opened it goes black. I have it connected to external monitor and that works fine, but I would like my portable computer back (as portable as the 17" beast can be... haha).

I can gather from the internets that there is a reed switch which allows the screen to turn on when the lid is opened, but it seems that can't explain the partial failure I am experiencing.

I also have a 12" Powerbook taken apart. If any parts from it would come in handy I would be more likely to get this thing fixed up myself.

You guys are the most helpful and knowledgable regarding hardware problems I have found in my searching. Any pointers to parts, guides, troubleshooting ideas, etc. would be so valuable. Thanks in advance,

Kristina

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Tom Owad's picture
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Re: Powerbook G4 17" aluminum; screen goes black when opened ...

Sounds like a cable is getting pinched. Check for damaged wires around the hinge. If you're lucky, a bit of tape will fix it.

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Re: Powerbook G4 17" aluminum; screen goes black when opened ...

Could also be a loose connection where the LVDS cable plugs into the back of the LCD panel. That is one really nasty, time consuming repair: you'll have to remove the top case and display assembly first. Then disassemble the display assembly, reseat the LVDS cable (put some tape over it to ensure it doesn't work loose again), then put everything back together. And hope that the repair fixed the problem.

Apple never even sent out bare LCD panels or LVDS cables for most of the PBG4 models: they just swapped out the entire assembly if a PBG4 was brought in for warranty. I don't always agree with Apple's corporate logic, but I think they may have been onto something in this case.

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Re: Powerbook G4 17" aluminum; screen goes black when opened ...

cwsmith wrote:

Could also be a loose connection where the LVDS cable plugs into the back of the LCD panel. That is one really nasty, time consuming repair: you'll have to remove the top case and display assembly first. Then disassemble the display assembly, reseat the LVDS cable (put some tape over it to ensure it doesn't work loose again), then put everything back together. And hope that the repair fixed the problem.

I've never touched a 17" machine, but on the 15" models it's possible to open the display housing without removing it from the computer. If you suspect the problem's inside the housing then it might be preferable to try it since, again, on the 15" removing the display housing essentially requires *completely* gutting the machine. (Even the motherboard has to come out and removing that means undoing a million screws and tiny cables and detaching it from the heat sink assembly, meaning you'll have to clean it and re-goop when it comes time to reinstall.) Maybe it's a different story on the 17".

So, one thing to test: When you open the machine up and the lights go off, is there still data being displayed on the LCD? You can test this by opening the lid up and shining a bright light through the Apple logo after it goes dark. If you see an uncorrupted Apple-shaped section of the desktop I'd say that your problem is either one of the backlight tubes, the inverter board, or the wiring in between, since if the LCD data cable were the problem you'd probably be getting a bright *white* screen. If you see absolutely nothing at all then I'd probably start trying to trace the problem from the motherboard end. I'm not sure where the sleep sensor is on the 17" machine (on the 15" it's under the trackpad), if it can be disconnected that might be a place to start.

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Re: Powerbook G4 17" aluminum; screen goes black when opened ...

Quote:

So, one thing to test: When you open the machine up and the lights go off, is there still data being displayed on the LCD?

Yes, the data is still being displayed, just no backlight. So I'll be checking around the inverter board first, I guess. Thanks for the tips.

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Re: Powerbook G4 17" aluminum; screen goes black when opened ...

Kristinaks wrote:
Quote:

So, one thing to test: When you open the machine up and the lights go off, is there still data being displayed on the LCD?

Yes, the data is still being displayed, just no backlight. So I'll be checking around the inverter board first, I guess. Thanks for the tips.

I wish you luck tracking it down. I'd probably start by taking the top case off the computer itself and tracing the wire that powers the inverter board from its connector on the motherboard to the hinge assembly just out of hopes that there might be some obvious fraying on that side. Opening the LCD housing itself is an incredibly annoying task. (I assume on the 17" the inverter board is in the same place that it is on the 15", inside that L-shaped extension of the lid between the two hinges. I guess I've been too lazy to look up a repair manual and find out.) If you get as far as having to open that the next thing I'd try is doing some continuity tests through the wire while rocking the display back and forth to see if it's either losing contact or shorting. If it does turn out the wire's bad inside the hinge itself that could be... amusing, to fix.

(I suppose you might be able to use the old wire to pull a new one through, but I'd worry that the hinge itself might be damaged so it's cutting or pinching as it opens and shuts.)

This is a long shot, but if you open the laptop enough so the screen comes on and then you rock the whole system back so the screen is in the position relative to gravity that it would be when open does it flicker/go out? If that happened I'd suspect a loose connection on the inverter board itself or the backlight tubes inside the LCD. (Again, long shot, it's undoubtedly hinge related.)

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Re: Powerbook G4 17" aluminum; screen goes black when opened ...

Eudimorphodon wrote:

I've never touched a 17" machine, but on the 15" models it's possible to open the display housing without removing it from the computer. If you suspect the problem's inside the housing then it might be preferable to try it since, again, on the 15" removing the display housing essentially requires *completely* gutting the machine.

Yeah, I have one I will be doing on a 12" soon and I am really hoping I can just put a new LCD panel into the display housing instead of going in the other direction.

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Re: Powerbook G4 17" aluminum; screen goes black when opened ...

Macinjosh wrote:

Yeah, I have one I will be doing on a 12" soon and I am really hoping I can just put a new LCD panel into the display housing instead of going in the other direction.

The really, really, *really* scary part is getting the LCD panel off the front bezel. Whoever thought it was a good idea to use glue to assemble a computer needs to be dragged out back and shot. I guess maybe it wouldn't matter so much if the panel you're prying off is dead already. :^b

(I've posted pictures of my 15" with the *working* LCD I managed to pry loose without killing... I have no idea how I managed it in retrospect. I keep intending to finish the project of making a picture frame computer out of that unit, but... just doesn't seem to ever happen.)

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Re: Powerbook G4 17" aluminum; screen goes black when opened ...

Eudimorphodon wrote:

The really, really, *really* scary part is getting the LCD panel off the front bezel. Whoever thought it was a good idea to use glue to assemble a computer needs to be dragged out back and shot. I guess maybe it wouldn't matter so much if the panel you're prying off is dead already. :^b

(I've posted pictures of my 15" with the *working* LCD I managed to pry loose without killing... I have no idea how I managed it in retrospect. I keep intending to finish the project of making a picture frame computer out of that unit, but... just doesn't seem to ever happen.)

Shudder. I can get a complete "display assembly" but I really don't wanna disassemble the whole thing. It wouldn't be a bad idea though just to blow the cobwebs and whatnot out while I'm there.

The one that gets me is the kapton tape that's practically blowing around inside the case by the time you get in there. And yet, the connectors are still more stout and less delicate than what they're putting inside the new ones...