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 Post subject: PowerBook G4/400 - No Video When Fully Assembled
PostPosted: Thu Feb 26, 2004 2:40 am 
Hey everybody,
This is my first post, so please bear with me... A friend gave me his 400Mhz TiBook after he dropped it. There were a few problems with the unit that have since been corrected. So far I've repaired the DVD drive and replaced the display inverter and the PRAM battery. Now, when I turn the unit on, I get mixed results with the screen. With all the parts in the unit, I get nothing, no picture on the LCD/S-Video/VGA out, but the unit DOES boot. It responds to keybard commands. I take out the HD with its ribbon, and the AirPort socket (there's no card installed) and the machine boots OK from CD. It is the strangest thing in the world. Put the parts back in and poof, its "blind" again. Any ideas? I'm hoping that the two ribbons are bad from all the bending they've suffered from opening the unit up, but the logic board (video circuits) may be bad. Please advise...

Thanks in advance!
-rwilliams


Last edited by Anonymous on Fri Mar 19, 2004 1:13 pm, edited 1 time in total.

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 Post subject: Hello?
PostPosted: Mon Mar 15, 2004 3:27 am 
Is there anybody who can help me with this problem? I need to get this machine working as soon as possible...

Thank you!
-rwilliams


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 Post subject: Hello?
PostPosted: Wed May 05, 2004 2:11 am 
Anybody out there?


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 Post subject:
PostPosted: Tue Sep 28, 2004 10:24 am 
Did you find an answer to this problem? I'm having a similar problem and after reading several posts, I'm wondering if a flickering display and problematic CD drive don't have a common root cause.


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 Post subject: similar problem
PostPosted: Wed Nov 10, 2004 2:10 pm 
Hello!
I've been having a similar problem for a long time now. A friend dropped her ti pb g4, cracking the blacklight among other things, and gave it to me to see if i could fix it up, and keep it if i could.

I have replaced the LCD, the PRAM battery, the PMU, and the inverter. Initially, it didn't work. I was getting a black screen on boot with about 9 black bars ~1cm spaced vertically across the screen. external monitor (VGA) DOES work directly off of boot, so I know the video card is working. I can completely run the system as long as there is an external monitor plugged in. I have not tested with the Svideo output yet.

For some reason it started working after I gave up on it for 2 weeks or so. It was working perfectly for around 4 months until for some reason the same problem occured again. First the screen flickered white occasionally, and eventually went completely black. Rebooting brought up the same old black screen with bars that I was seeing at first. It still isn't fixed.

In my extensive research that I had done for this problem, I have come up with a few possibilities on why this may be occuring:
1) there is/was a short in the system somewhere, frying something with the video AFTER GPU processing
2) PMU got fried and isn't giving enough power to the LCD to push the signal from the logic board to the LCD. Doesn't quite make sense, but could happen...
3) hairline fracture in the logic board that I can't see, causing a loss of signal when passed to the LCD cable output.

I don't think that it is a problem with the inverter, simply because I would be able to see SOMETHING on the LCD other than black. If I boot without the LCD data cable plugged in to the logic board, I get a white/grey screen. So the inverter is getting power up there.

It is likely something with the data cable, but when the problem happened initially, I tried a different cable and was having the same problems. So it may be somewhere between the data cable and the GPU (which is an ATI rage mobility 128, i think).


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 Post subject: similar problem
PostPosted: Wed Nov 10, 2004 2:20 pm 
oops, sorry, it got sent before i finished. i don't see a way to edit these posts after they got sent. ("blacklight" above should be backlight, of course.)

So right now I have a new PMU en route, which I will install and try out. If it works, i'll let you know.

I haven't tried booting without the RAM installed, but get the same result with the HD and DVD/CD drive taken out. Haven't tried booting off of CD.

It was working fine over the summer, and actually started working in Hawaii, with pretty humid air. Now that it's winter(ish) and the air is getting drier with a lot more static around, I'm wondering if climate has an effect on it. That would make sense if there is some sort of a short happening, but i can't think of a way to test it. Maybe take it into a steamy bathroom?

Anyways, now that I have spilled the guts of my problem onto the internet, hopefully we'll find a solution. I think a similar problem happens fairly commonly, I just haven't found a good solution yet. Keep the thread going.


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 Post subject: PMU ?
PostPosted: Thu Apr 26, 2007 5:03 am 
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Joined: Thu Apr 26, 2007 4:59 am
Posts: 3
I have a similar problem with a G4/400 that freezes the internal LCD occasionally and lets it go dark. The system continoues working and the external VGA is not affected. Logic board is o.k., the LCD supposedly too.

In your case, has the replacement of the PMU cured your problem?

Thanks for your reply!


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 Post subject:
PostPosted: Thu Apr 26, 2007 6:41 am 
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Joined: Mon Feb 24, 2003 1:58 am
Posts: 940
You say the LCD is dark. When the LCD goes does, if you look very closely at the screen, are you able to make out faint images? If so, your inverter board is likely failing on you. If the image actually freezes on the screen, then you're going to be looking at either a display or logic board replacement. The fact that an external LCD works fine suggests further that you'd be looking at an LCD replacement.

-Bradley
PowerbookMedic


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 Post subject:
PostPosted: Thu Apr 26, 2007 6:50 am 
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Joined: Thu Apr 26, 2007 4:59 am
Posts: 3
i forgot to mention: the back-light is o.k. The image freezes, then rasterizes and finally blurs away from the center to the edges.

The LCD with the data cable was changed with no result. The same with a known good logic board.


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 Post subject:
PostPosted: Thu Apr 26, 2007 7:43 am 
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Joined: Mon Feb 24, 2003 1:58 am
Posts: 940
When you changed the LCD with display cable, did you get the exact same issue, and the exact same issue with a replacement board? Where did you get the replacement parts from? The problem can only be the LCD (with cable) or the logic board....or in an extremely rare instance, both together.

-Bradley
PowerbookMedic


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 Post subject:
PostPosted: Thu Apr 26, 2007 3:34 pm 
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Joined: Thu Apr 26, 2007 4:59 am
Posts: 3
with the original display, the screen works fine if the pb was off for a day or two and then suddenly freezes and goes black. The replacement display goes black from the start. Both displays behave the same even if I have a replacement logic board installed.

The replacement display was purchased from ebay and was said to have been working until it was sold. The logic board came from a pb repair service in germany as a tested unit. So the odds are against the displays?


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 Post subject:
PostPosted: Fri Apr 27, 2007 10:44 am 
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Site Admin

Joined: Mon Feb 24, 2003 1:58 am
Posts: 940
Definately sounds like the display. The parts you find on eBay are generally crap. I'd try to pick up another one, verify it is the issue, and get your money back from the seller.

-Bradley
PowerbookMedic


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