Macintosh Portable (1989) - Learning about a "New to Me" Computer

One of my recent acquisitions in the collection is an Apple Macintosh Portable.  This computer was released in 1989 by Apple, and was the first Portable computer (Battery powered computer) from Apple.  

At that point in time, I was interested in computers, but pretty unaware of what was going on in the industry, and certainly not aware of high-end business machines.  I've recently developed a strong interest in the 68K Macs and because of the high cost and low number of these machines that was produced, I never thought I'd be able to afford one.  I ended up getting this in exchange for labor helping someone clean out and price a large lot of retro computers.  I was a bit concerned because a fellow retro computing enthusiast told me that it took collecting three Portables before they were able to get a single working unit.   I was hopeful however because of the care that this collector had obviously taken.

My example is from 1990, near the middle of the run, this computer was not a big commercial success for Apple.  The cosmetic condition is excellent but from what I've learned online, since these were made during the early '90s capacitor plague, they all need a Recap.  The first videos I like to watch on a new computer that I'm unfamiliar with are from Jason's Macintosh Museum, here's one that shows how to open the computer.

At this point, I knew that I'd need a battery in order to start the Macintosh portable, thanks to some good advice, I was made aware of this solution for buying a new one online from this eBay seller, Alaska360.  While I was waiting for that part to come, I was able to dive in on the Recap.

Bruce from Branchus Creations has provided an excellent recapping guide here.  Bruce's guide is for the later Backlit model, M5126, and my unit is the first M5120 model, which I believe to be more common.  I used Bruce's guide as a starting point, and made edits to update it for the 5120.  I will include my edited version of Bruce's guide here.  Also, I'd highly recommend watching Bruce's video on the topic, he's got a high level of both knowledge and skill at repairing these machines.

I did my recap using parts from Digi-Key, which we are very fortunate to have right here in the state of Minnesota.  This went OK, but as it was my first time around the main challenge was that the Radial Caps I'd ordered had leads that were too thick to fit through the holes in the circuit board.  Here's my updated Bill of Materials for this,  I've updated the part number of the Radial Caps too 0.6mm leads instead of 0.8mm leads, although I haven't tested this yet.  Let me know via email or in the comments below if you have success with these caps with the smaller leads.

So, after the recap was complete and the battery arrived, it was time for the "Moment of Truth", the power up test.  I was super excited to see that the computer worked!

Getting to play around with this computer has been one of the major highlights of my year in retro computing.  The SCSI hard drive works, making it one of the few functioning SCSI drives that I have.  This SCSI drive has a proprietary connector, but if it does stop working the eBay seller I mentioned for the battery also has a special SCSI adapter that allows the Portable to run off SCSI2SD.  I expect this drive will die soon and that's an upgrade that will be on the near horizon for this machine.

There were a few problems with my portable.  First, I noticed there was no power up sound.  I suspected something was wrong with the sound circuit because I knew that during the recap several pads had lifted.  I did my best to repair that damage, but I've had trouble with the sound circuit on computers from this era before.  So, I started to search the forums, and again based on advice joined a "New to Me" forum for 68K macs, the 68KMLA forum.  This thread seemed to be on topic, so I joined in.  I got some really great advice, and I was able to resolve the issue!  I did have to take the entire computer back apart again to get at the board.

The second issue is more concerning, the display appears to be degrading.  If you look closely at the image,  you can see a line of about may 50 dead pixels at the top left corner, right along the line of the menu bar.  This was an image I took right after getting the machine running again.  Since then, another line has appeared along the right hand side.  I do not know yet if this screen is at repairable, it would be great if this was just a loose contact or something, but I don't anticipate that it will be repairable.  This is Apple's first Active Matrix screen, and I think it may simply be failing.   I'll keep my eyes out for a donor, and in the meantime, enjoy using the machine!