Notebook Computer Rebuild

Long ago, when I graduated from high school, my parents bought me a notebook computer. It was a Leading Edge 386SX-20, which at the time was a pretty good machine, though not really a powerhouse. It served its time well, doing everything from note-taking to writing term papers to compiling C in class. Time eventually took its toll, however, and it fell victim to a crack in the video section of the motherboard. It still worked, but only if you twisted it just so and kept it from torquing around. Clearly, the plastic chassis wasn't up to this task, and several attempts to stiffen it proved fruitless. So it got shelved.

One fine day in the fall of 1999, I was sorting through my computer parts boxes when I ran across my tired old notebook. Upon firing it up, I quickly determined the following facts:

The battery pack was a paperweight.
It still worked if I plugged it into the wall.
The CMOS battery had died while in storage.
There still wasn't much I could do to reinforce the plastic chassis.

Of course, being the incurable tinker that I am, I couldn't just let it sit there in the box and collect dust. Instead, I began an extensive project to rebuild my notebook computer, from the ground up if necessary, to get it running reliably once again.

I was clearly insane.

What the notebook originally looked like (more or less).

Phase I -- Assessment

The first step was to assess the damage, and come up with a plan to fix it.

Removing the keyboard, I found no obvious damage to the computer. In fact, it looked exactly the same as it had during my previous attempts to shore up the motherboard and keep it from flexing. The CMOS battery had died in storage, and looking at it, I realized I would have to find a replacement for a somewhat specialized battery. That might prove a problem in the future, but it wasn't the most immediate issue. The battery pack provided a couple of interesting mysteries. Prying open the shell, I found not only the expected C-size NiCd cells, but also a couple of "mystery components" that I didn't recognize.

The first one was a silver-colored device, wired in series between the pack's halves. I assume this was some sort of safety cutout device to prevent the pack from dumping a full charge across a dead short. It was nestled down in between a couple of cells, so it may be thermally triggered, too.

The second device was a black epoxy unit connected between ground and one of the connections to the power brick. I assume that this is a temperature sensor that lets the charging circuit in the brick know when it's reached a full charge. This makes sense to me, since the new battery was of a considerably higher capacity and took a longer time to charge fully, though the original power supply had no problem adjusting to it, and it still got a full charge every time.

All that stuff fit inside that tiny little package!

Phase II -- Planning

I had an idea of what I was trying to accomplish with this project: I had to build a new rigid chassis for the computer, while still attempting to keep it portable. I was going to have to replace some components, and finding exact units was going to be impossible (Daewoo Industries having dropped their Leading Edge consumer computer division long ago). It was clear that I would have to do a bit of rearranging to make everyhting fit into a similar footprint.

...If I were to make everything fit.

There had always been some design issues that had bugged me about the original machine. The external power pack was a major pain, especially considering how I had spent so much time running it plugged into the wall. Despite the convenience of extra capacity, the battery proved to be a pain because it bulged out of the computer's outline. Why not integrate the brick into the new chassis, and rearrange the battery to lay down inside the outline as well? Heck -- while I'm at it, finding a direct replacement for the CMOS battery was going to be a pain, so why not just kludge in a replacement cell of whatever physical size I could find? I was going to be adding to the footprint anyways; why not spread out a little? Get the hot power converter away from the rest of the electronics. I could even put all the power-handling components in their own compartment in the new chassis, and provide some ventilation for it, including forced-air cooling whenever it was plugged into the wall. This had some promise!

I sat down and figured out that using plywood for the rigid chassis, I could arrange the important bits in about the same footprint, but that it was going to be considerably thicker than the original unit. This more or less eliminated the possibility of a classic "notebook" design, but _did_ owe itself to a vertically-oriented "lunchbox" chassis layout. If I mounted the LCD screen on the chassis and moved the keyboard to the lid, it just might work out.

An early test-fit to see if everything could fit into the chassis.

Phase III -- Execution

The power block went together without a hitch. I purchased six C-size NiCd cells and built a duplicate of the battery pack, with the major exception that this one was laid out long and flat, rather than being all bunched up like the original had been. This was connected to the brick via the much-shortened original power cable, and to the power converter through a 4-pin connector scavenged from a floppy drive extension cable. I also built a 12-volt power supply to drive a low-profile blower which will ventilate the box when it's plugged into a wall outlet.

The LCD's cable was lengthened through a simple but time-consuming process of soldering and insulating 22 individual wires, two times apiece. Being as the original screen mounting tilted back for viewing and the new chassis required it to tilt up, I had to find a way to rotate the LCD unit 180 degrees within its mounting. Fortunately, this proved to be a fairly simple matter of just trimming out a ridge or two and re-mounting it upside down.

The motherboard was the next thing to tackle. This was rigidly mounted to a piece of plywood to which a sheet of metal mesh had been attached for shielding purposes. After a great deal of legwork, I came to realize that I simply wasn't going to be able to find a long piece of super-flat shielded ribbon cable, and proceeded to improvise a solution. After much further failed experimentation, I eventually just decided to mount the floppy back in its original position and cut a hole in the side of the chassis for access to the floppy. I'm not particularly happy with this arrangement, but it's the only one that seems to work.

The notebook's new power block.

Phase IV -- The Test

Up to this point, I hadn't actually applied power to the computer since removing it from the chassis. For all I knew, I had toasted the motherboard the moment I removed it from the box. At this point, I had the power block, the LCD, and the motherboard all mounted on their respective decks, so there was no real reason why I shouldn't fire it up for a test-run. I figured now was a good time, since There were only two possibilities:

The computer boots up and works, in which case, I continue on with the project.
The computer is slagged and useless, in which case, I haven't lost anything -- it wasn't working to begin with, so no net loss.

The obvious results are shown below. (Obvious in that if it hadn't worked, I probably wouldn't have bothered to write a web page about it.)

It's ugly, but it works! (Yes, that's WinDoze 3.1)

Phase V -- The Rest Of It

Well, that's about as far as I've gotten. As of this writing, I've got it more-or-less working, including the floppy drive (The picture above was taken before I had worked out the cabling for it). I'm in the process of fabricating a front panel, to which will be mounted the controls, LEDs, ports, and power switch. I'll be posting more views as I make progress.