My lovely loyal laptop (PowerBook G4) has developed some strange behaviors over the last few months. Things degraded to the point where it would “randomly” enter sleep mode in the middle of regular tasks. I think I fixed the problem tonight: it was not the track pad thermal sensor, or any of those other problems. The failure seems to be in the ambient light sensor.

If this sounds interesting to you, then read on for the full story! The first thing i noticed was that the “breathing” of the sleep light got inconsistent when the lid was closed. Then the screen would flicker occasionally. Next, the narcolepsy started. At first, Lappy seemed to fall asleep at very random times. Luckily, it would wake up right away with no problems, but it was still pretty frustrating. Slowly, I started to detect some patterns. Resting my hand on the right side of the computer triggered the issue more often. On some evenings, hitting the delete key would put the computer to sleep every time. This made me improve my typing skills! Eventually I noticed that the problem was significantly more pronounced at night… and that got me thinking.

All the googling i could do turned up nothing but trackpad temp sensor issues. I had eliminated this as a culprit early on, but assumed something similar internally was shorting out and causing the computer to protectively shutdown. The problem worsened, and eventually got to the point where i could wave my hand over the right side of the keyboard to make it sleep. This led me to believe the problem was the built-in ambient light sensor that controls the keyboard backlight and auto-adjusts the LCD backlight. Further searching turned up a short comment that sounded related, nestled towards the bottom of some web article (barticle?). I contacted the poster (whose info i can no longer find to credit properly), and he informed me that yes, he had the same light sensor issue, and fixed it by opening up his computer and removing the sensor. That was exactly what i was looking to hear!

That was months ago. You see, i had just gone through upgrading my hard drive, so i knew how tricky opening up the laptop can be. I wasn’t eager to repeat it, so i put it off. And put it off. And off further. I put it off until things were so bad that i couldn’t hold my laptop on my lap at night, because slight movements or people walking by, or a lamp flickering would trigger sleep… Waking up was getting harder and harder as well, and it would often sleep-cycle (especially at the exciting part of whatever movie we were trying to get through).

So, i finally got around to it, because i’m really gonna need the reliability soon. Disassembly the second time through was much easier. I used the same basic walk-through i had used previously, but this time knew some additional tricks.

There are over 20 very small screws that need to be removed to lift the keyboard (exposing the logic board) on a powerbook. They come in about 5 different sizes. To keep track of what sizes go where, i drew a quick outline of the computer, top and bottom, and marked all the screw holes. As i removed each screw, i punched it through the paper to keep it in place. This vastly expedited the reassembly.

Here are some other notes, in case you ever need to do this:

• Opening the case voids your warranty. Make sure Apple Care can’t help you first.
• Warranties are for chumps. Void away! You will need a 1.5mm allen wrench, and a set of small screwdrivers.
• Get a bigger hard drive to install while you are inside. It’s easy once the case is opened!
• Use the largest size screwdriver you can. I started with the smallest, but it was more likely to strip the screws (scary!)
• You don’t need to loosen the screws on either side of the DVI port.
• The DVD drive latches are a pain! Go ahead and bend out the metal just above the dvd slot. Being able to see the latches makes things much easier. You can bend it (most of the way) back in when you are done.
• You don’t need to remove the sensor on the left — you can simply unplug it and tuck the cable away. I’m not sure i needed to mess with this one at all, but didn’t want to have to open the case again.
• The right sensor seems to make its electrical contacts by simply sitting on wires! No wonder it is shorting out! So much beautiful design inside this case, i’m not sure how this was overlooked. One screw, and this just lifts out.
• Go ahead and blow all the dust out of the case while you are in there.
• Boot up and test things out before screwing everything back together.
• I bent out the little ledge where the DVD slot latches hook on, so they wouldn’t be able to hold so well in case i ever need to get in there again.
• When you are re-attaching the screws, be sure not to over-tighten them. They strip fairly easily, and don’t need to be super-tight. Flush-and-a-half should do the trick.
• Make sure you get all the right-sized screws back where they belong!

That should do it! Hopefully, that is the last i see of the narcolepsy issues. Now Sarah will be the only one sleeping through movies! ;-D

I have some pictures and hope to get them posted soon.