Blog Relaunch: PowerBook Surgery

When I started Facebooking and Twittering, the activity on my blog went from little to none.   I hadn't touched it in a couple of years and the Movable Type installation was woefully out of date.  At the same time, the open source hardware movement has inspired me to try to contribute a little here or there...  So I moved the technology-related postings from the past to a new platform (that I don't have to maintain) and decided to start posting bits here and there on what I've been up to in the workshop.

The most recent activity on the bench was major surgery on my laptop.  Now mind you, my laptop is a 6+ year-old Apple PowerBook (PB) G4, so when the power jack got worn out, I thought this would be a good reason to finally upgrade to a shiny new MacBook pro.  However, given my wife's desire for new windows on our home and her quickness to remind me about the Self-Repair Manifesto poster in my workshop, I decided it would be best to take a crack at fixing the laptop myself.   After all, we do have a relatively new iMac in the house, so I have access to a faster machine.  The PB is still perfectly good for development tools like gcc and Eagle (and I don't have to share it), so it's definitely useful for me to keep it around.

First, here are a couple of photos of what I was replacing.  The Apple "Magsafe" connector didn't show up until the MacBook.  What they used on the PowerBook is a modified 3.5 mm phono plug.  The shroud that surrounds it keeps you from plugging it into a regular audio jack and serves as a connection for the green/yellow LED in the plug.  I believe jack/plug combo was failing because their contacts get pitted over time from the arcing that occurs from plugging in an energized power adapter.  Over time, the pitting itself makes the arcing more apt to occur and the problem snowballs.  (More arcing -> more pitting -> more arcing...)  It's difficult to see in the photo, but there are whole pieces of the ring and sleeve missing in the plug.  There are a few spots where only the plastic insulator that sits inside the connector remains.

As noted in a previous post, I have torn my laptop open before using the iFixit Repair Guide.  Once again, their information did a wonderful of guiding me through the process of removing the almost 5000 screws that hold the laptop together.  After about 30 minutes, I got down to the DC input board which is buried under just about everything else, including the motherboard:

Now, before I started this endeavor, I Googled a bit to see if anyone had posted any on doing a similar repair.  I found an blog article where someone replaced the original power jack on a 15-in PB with a standard coaxial DC power jack, which is exactly what I planned to do.  So while I had some guidance, I am glad I did some investigation on my own before blindly following those directions.  What I found was that the polarity marking in the photos did not match what I found by checking continuity and voltages on my own.  (Luckily, the connection between my jack and plug was still working enough so I could measure the voltages on the jack.)  The 15" PB power jack mounted with a different PCB arrangement than the 12" PB, so it's quite possible Apple used a jack on the 12" PB that had a completely different footprint.  Either that, or the guy who wrote the article marked his photo wrong.  Either way, I'm glad I checked things out before smoking my PB's DC-to-DC converter. 

After I removed the DC input board, I did a test fit of the new coaxial jack.  Once I verified everything would fit, I carefully removed the old jack from the PCB:

Then I prepared the new jack with some sort wires and heat shrink tubing.  (Note the PB's insides scattered all over my bench...)

Finally, I reinstalled the PCB and put the machine back together:

As you can see, the PB worked when I put it back together.  It actually took two tries; the first time I put it together, the display had no raster.  I opened it back up and reseated the video cable and success!  I am happy to report that the power adapter works and charges the battery as well.  I guess I have to come up with another excuse to buy that MacBook Pro...

One last note: In the article I cited above, there is a discussion in the notes about a sensing voltage set by a resistor connected to the tip of the original plug.  I decided to leave it out since I only have a 45 W adaptier.  Without seeing the sensing voltage, the PB charges at the slowest rate.  (At least that seems to be the consensus in the article comments.)  I've kept an eye on the power adapter and it doesn't seem to be heating up, so I think I'm safe.