Powerbook 867 15inch - Sreen goes blank

[Highway of Life]

It started happening two nights ago.
All the sudden my backlight shut off.
It did not go to sleep, and the screen was still on, I could put a flash light through the back and see items on the screen.
So I plugged in an external monitor, and my backlight instantly came back on. But after a few seconds it turned off again.
If I change the display settings it will come on again, and after a random amount of time, the back light will turn off.
Same thing if I turn mirroring on or off, it will come back on, and after some time, it will turn off again, usually within 30 seconds.
Same thing if I put the Powerbook to sleep, then wake it up, the Backlight will come on, and after some time, shut off again.

On occasion, I can be working on it for about 15 - 20 minutes before it will shut off.
If the Powerbook awakes from sleep and I don't touch it for over an hour, it will stay on. But then as soon as I start working on it, after a few seconds the backlight will turn off again.

I found a thread on apple discussions addressing a similar issue, so I tried a few of the tips: First I trashed the com.apple.finder file, then reset the PRAM. It still did not work, so I reset the PMU, then reset the PRAM again, and promptly repaired permissions.
Still no change.

Every-time the Powerbook starts up, or wakes up from sleep, the backlight will be on, then shut off after a number of seconds or minutes.

Nobody ever talks on the apple discussions so it's almost impossible to get any more help there.

Tonight, I took the Powerbook apart and checked all internal connections.
After putting it back together, I noticed no change in the behavior.

Any tips?

Thanks in advance,
- Highway

System stats:
Machine Model: PowerBook G4 15"
CPU Type: PowerPC G4 (3.2)
CPU Speed: 867 MHz
L2 Cache (per CPU): 256 KB
L3 Cache (per CPU): 1 MB
Memory: 768 MB
Bus Speed: 133 MHz
HD Capacity: 40GB
External Firewire/USB Drives: None
Internal Cards: None
PCMCIA Cards: Wifi adaptor
System Software: Mac OS X 10.3.7
VRAM: 32 MB

Display
ATY,RV250M9:

Type: display
Bus: AGP
VRAM (Total): 32 MB
Vendor: ATI (0x1002)
Device ID: 0x4c66
Revision ID: 0x0001
ROM Revision: 113-xxxxx-106

Display:

Type: display
Display Type: LCD
VRAM (In Use): 16 MB
Resolution: 1024 x 768
Depth: 32-bit Color
Stretched: Yes
Mirror Status: Hardware Mirror
Online: Yes
Mirror: On

Display:

Type: display
Display Type: NONE
VRAM (In Use): 16 MB
Resolution: 1024 x 768 @ 60 Hz
Depth: 32-bit Color
Main Display: Yes
Mirror Status: Master Mirror
Online: Yes
Mirror: On

[epooch]

I had a similar problem do to a short in the wire going through the hinge on my iBook. Selecting a new resolution in the displays system preferences would turn the backlight back on for a while.

--Eric

[Highway of Life]

UPDATE

Well, two days later. The screen (backlight) has been a bit more stable.
Over time, it has stopped blanking out, yesterday, it only occured four times.
Today, none at all. It only flickers black now.
But less and less all the time.
Two days ago, the only way to keep my screen (backlight) on was to put the powerbook on my lap (as opposed to having it on the desk). For some reason the screen would not turn off if I had it on my lap.

[everettaaron]

Hey, Highway! love the icon! Did you ever find the problem with your backlight. I was given a G4 powerbook for our ministry and the backlight has not worked on it since I recieved it. It flickers when you power on or switch display modes or turn mirroring on or off, but will not stay on.

Thanks and God Bless!!
Everett

[Highway of Life]

Hello Everett,

Thanks.
Yes, I did find and fix the problem with my backlight.
It was the power inverter ($70 part -- $50 if you find the right retailer. )
I found out because 1) An external monitor would always work. 2) It would work for a few sececonds everytime I switched the display res. And the cake topper: 3) It blinked every time I lightly tapped on the DVD drive.
Which happens to be located right next to the inverter.

I replaced the inverter (15-20 minute process) and it has worked great!
Do be very careful when replacing a part in your powerbook, as one wrong move could easily damage another item.

Have a great day.
Blessings man!
- Highway