Starting the New Year Right - Macintosh 512K - Part 1

Happy New Year, everyone!  I'm starting the new year right with an exciting addition to the collection, the Macintosh 512K, released in late 1984.

I'm really enjoying this system, and started out by doing a bit of "Computer Archeology" on this system.  One of my favorite things about Retro Computing is trying to figure out the back story on the systems.  For a couple of my systems I know they were purchased new by a family and held by them till I got them, but most of the systems have a certain amount of mystery associated with them.  This system has a couple of service stickers on it, and the previous owner (a fellow collector who has been doing this much longer than me) told me that he had swapped the Logic Board to get this machine back up and running again.  So I actually have more background on this computer than I do on most of the computers in my collection.

This system has a case from an Original Macintosh with a Serial Number that indicates that it was made in the 14th week of 1984, which I believe makes this case one of the first one hundred thousand units sold.  However, like so many of these units it was upgraded too a 512K board early in its life.  There's a sticker inside the chassis that indicates it was serviced at Heathkit Electronic Center on 6/15/1987 and this sticker has 512K printed on it, which seems to indicate that the upgrade had be carried out on or before that date.  The floppy drive and Power Supply board also have 1986 dates on them, so they may have been swapped at that time as well.

There is another sticker on the bottom of the chassis for a repair carried out at Midwest Visual Equipment in New Berlin, WI on 12/30/92.  This demonstrates that the machine was still being used 8 years after it was new, and used enough that it was worthwhile to have it serviced again.  I have no idea when the computer would have stopped being used, but within 2 years after that service the Power Macs were starting to be introduced.  That would have been quite the performance gap at that point in time.

As I've already mentioned, the main logic board was replaced more recently than any of the other repairs.  I don't know the date of the board itself, but the latest date code on the chips is from the later half of 1984, so this may have been a board from an earlier 512K example.

This computer has an 800K floppy upgrade.   I didn't think I'd be able to use that drive capacity since the 512K has the smaller ROMs (There's no code on the ROMs to run a double sided drive), but I've just learned that if you use System 3.2 with HD20 hard drive support, the ROMs get patched to support double sided drives both internally and externally.

All in all, I couldn't be more pleased with this addition to the collection.  I've always wanted one of these early Macs.  This is a good, solid machine in great repair that I don't have to feel bad about using since it's not a museum piece, which is perfect, since I do intend to use this machine.

I had quite an interesting challenge getting a workflow setup for disk imaging to create 400K disks for this machine, stay tuned, I'll go into that in Part 2 of this series.

What was your first Macintosh?  Let me know in the comments below if you have stories about these early Macs.

The Macintosh Plus - The Best Retro Macintosh?

The Macintosh Plus is one of my favorite retro computers in my collection.  It's understood that the first Macintosh has the most value, as does the first of anything, but in this case the Mac Plus is the last of the "original" Macs.  It's got the same industrial design (the same shape), and the early machines in the run have the same color as the originals.  These computer are significantly more useful, as they can have up to 4MB RAM, an external SCSI connector, and can run System 7.  Also, the double sided drive allows the system to read and write the original disks, but is also more practical should you want to run off floppies for nostalgia purposes, since you can have a boot disk and a program on the same disk.

The SCSI port is compatible with the SCSI2SD hard drive replacement,  I have two examples of the Mac Plus, a unit from 1986 and another from 1989, and they both work with SCSI2SD after using these settings.  From reading online, I believe that there were some special features added to the SCSI2SD to support these machines, but it's possible that early ROM versions of the Plus won't boot off SCSI2SD.  Personally, I've gotten Mac OS Version 4.1 up to 7.5.5 installed and booting off of 2GB partitions, but I didn't set up SCSI2SD to simulate a Mac drive, so I had to use Lido to get the drives setup.  I also have a FloppyEmu, which I normally use on the Apple IIs, but it's quite useful for bootstrapping these machines when it's time to install a new version of Mac OS, or load programs.

I've used both the SCSI2SD 5.5 in the external case, and most recently, I've transplanted a Version 5.1 device into the External SCSI enclosure shown above to simulate a somewhat more period correct look.  I documented that build in another article here.

My 1986 Mac Plus had been experiencing problems with overheating.  I recently brought it back onto the workbench, opened it up, and was able to replace a bad capacitor on the Power Supply board that had started to show signs of leakage.  I had not noticed this before during previous repairs, so I went carefully over the entire board.  I also ended up breaking off the fuse holder on the board, but that was a very inexpensive part from DigiKey.  While doing these repairs, I also installed a 12volt 60mm fan that I had on hand inside the case.  The machines’s been running much better now after a couple of day long burn in sessions, so I’m greatly relieved to have what is currently the oldest Mac in my collection working well again.

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!

Apple II Plus - Trash to Treasure - Part II

In the last update, we left off with the Apple II Plus able to power on, but without testing either the keyboard or any of the hardware.  After the replacement keyboard cable arrived, I plugged the keyboard in for the first test.  Unfortunately, with the Keyboard plugged in I was getting repeated keystrokes over and over again.  I could tell that the Keyboard was working to some degree because when I'd press a key the correct key would come through, but then fill the screen with repeating characters till the next character was pressed.

I started troubleshooting by doing Google searches on the Internet.  My first understanding from what I'd read lead me to believe that the Keyboard Encoder board could have failed, which is a separate board that is attached too but not part of the keyboard on the Apple II and the II Plus.  I found this modern replacement for the Apple II Keyboard Encoder and ordered it.  The great thing about this solution is that it also includes a PS/2 port for attaching a modern keyboard. With this board and a modern keyboard you have a complete known good keyboard solution for the Apple II or the Plus.  After this arrive and I plugged it in, it had no effect, the problem persisted.

So, understanding that this problem was not with the Keyboard or the Keyboard Encoder board, this pushed me back to looking at and considering the motherboard.  I had read about the book "The Apple II Circuit Description", and so after my failure to properly diagnose the initial problem, I decided it was time to dig in and read this.  I read through the introductory parts of each chapter, and also dug in a bit on the Keyboard I/O schematic.  Feeling a bit unsure after the disappointment with the Encoder board, I decided it was time to reach out on the Vintage Computer Forums.  As has happened before, I received some great advice.  It ended up being one and only one bad 74xx Logic chip, replacing this with a new device solved the repeating key problem!

After testing the keyboard, I determined that four of the keys were not working, the previous cleaning had not been enough to rejuvenate them.  By using the Ohmmeter I was able to determine that the key switch contact was not closing.  Having repaired individual key switches before using a procedure demonstrated on Adrian's Digital Basement, I removed the problem keys by desoldering them from the keyboard, dis-assembling them, and carefully cleaning the switch plates.  These ended up being Alps short-step switches, so the mechanism was a bit unfamiliar.  I found that for some of the switches I had to spray contact cleaner in between the plates, then blow it out with compressed air a couple of times to clear the contact of whatever was preventing the circuit from closing.

After getting a complete working Keyboard, it was time too test the RAM.   I've attached my Disk Controller II card from my Apple IIe, and FloppyEmu to this system, but I did not have any success loading software onto this Apple II Plus, other than successfully loading DOS 3.3.   It turned out that part of my problem was not understanding how the DOS system worked, I needed to go back and read about that, too.  This simple list of DOS commands was helpful.  After I learned that this is a 48K Apple, and that because it's an Apple II Plus, it has Applesoft in ROM and not Integer Basic, then I started to understand why I could load certain programs and not others.

At this point, I was finally able to load and successfully run Apple-Cillin diagnostics on the machine.  Using this tool I was able to diagnose that the machine did indeed have some bad RAM.  By doing trial and error using the first bank of 16K of RAM, I was able to condemn four RAM chips and set aside another group of RAM chips that are working, but their legs are broken. Again, due to the fantastic Retro Computing community's online contributions, I learned that the electronics distributor Jameco still has the correct RAM chips in stock.  I ordered a bunch in order to replenish the top bank to bring this machine back to 48K, and have a few spares as well.

With either 32K or 48K, I can't run most of the Apple II software that's out there from my childhood because most of that requires a 64K machine, but I have the Apple IIe for that.  I think I'll try to outfit this machine to behave as an original Apple II.  Original Apple II prices have gotten a bit crazy, but I did find this cool modern card, a MultiROM card that allows the machine to load Integer Basic, or boot to the monitor and behave just like an original Apple II.  I put this on order, and with the the current situation with shipping during the Holidays, this project will go back on hold for a while.

Thanks for reading!  Let me know in the comments or in email what memories you have of the Apple II, II Plus, or IIe.  One of the things I'm currently researching is what people did with their Apple IIs with less than 64K RAM, what games were popular from the late seventies up till 1981 or '82?

Apple II Plus - Trash to Treasure - Part 1

One of my goals in Retro Computing is to learn about older and older computers, and work my way back in time, one generation of computers at a time.  The nostalgia factor is certainly important for me, but I’m also interested in the tech that came before.  In my own retro computing development, I’d been keeping my eye out for an Apple II Plus machine.  I have an Apple IIe that I’ve already mentioned, and have been interested in the experience of using the original Apple II's since I’ve never owned one of the original “Trinity” of home computers.  Finding an original Apple II (not a Plus) seems a bit out of my price range at this point, but perhaps someday I’ll be able to repair an original Apple II.

My opportunity for a II+ came in mid November of this year, when a trusted retro computer seller on Craigslist posted a Bell and Howell “Darth Vader” computer in need of some serious help.  As Apple fans will know, this was a partly re-branded Apple II Plus, Bell and Howell painted it black, and since it’s a bit more rare it’s more valuable.  The seller and I had a phone conversation about the state of the machine, which was poor, but I was able to convince him to sell me the machine regardless of the state.

The state of the computer was not good.  The biggest problem with this computer was that the top cover had been removed before the computer was stored.  This meant that dust and dirt got inside.  I even found a couple of acorn tops as I was cleaning inside.  The main board had a significant amount of dirt on it, and there was one chip (one of the ROMs) that had bent pins  It seems likely that something very heavy was dropped onto this chip causing the pin legs to bend.

So on intake, it was obvious that I should not even try to power the machine on without doing a lot of cleaning first.  I started by taking the top half off the case, removing the power supply, main logic board, keyboard, and backpack from the unit.

I started with the logic board.  I used the cleaning method that Adrian Black has been demonstrating, warm soapy water in my basement laundry sink.  I used Dawn dish detergent, warm water, and brushes for the initial cleaning.  It took quite a bit of time because there are more than 80 chips on the board that all needed to be cleaned around, but it was very gratifying to see how much better the board looked after.

Also, at this point I was able to get a look at the date code on the board and discover that this II Plus was made in 1981, so this would have been the third year of production for the II+, starting in 1979.  After the initial clean of the logic board, I shifted gears to the power supply.   I had already serviced the power supply in my Apple IIe, but this one had an additional rivet on either side that I had to drill out.  The RIFA cap was certainly on its way out (bulging) so I'm glad I saved the smelly mess associated with a power on test.  I removed and replaced with a new X type filter cap that I had in stock.  When I put the power supply back together and tested voltages, it was not working correctly.  I remembered that as I was re-assembling it, the circuit board had flexed quite a bit.  Since this board has a heavy transformer in the middle, I think this design is prone to getting cracked solder joints at the transformer.  After I reflowed the joints on the transformer and several other components while I was at it, the power supply was working with all voltages reading good.

Next, I tackled the keyboard.  One of the things I dislike about the Apple II Plus is the use of ribbon cables with DIP connectors on the end.  I didn’t realize how fragile these were, and as I was taking the computer apart, I broke pins on the interconnect cable between the logic board and the keyboard.  Thankfully, I was able to find this article online, I ordered the replacement cable from DigiKey, and it is on the way.  This keyboard has the SKCC Short Stems with the extenders installed, and it ended up being significantly less dirty than the previous one I’d cleaned. My son especially enjoys keyboard cleanup (I think it reminds him of Legos), so he helped me with this part of the project.  We pulled all the keys and gave them a soak, he helped me go over them all with a toothbrush, they look great.  I then worked on the keyboard deck, using the same procedure I described in the Apple IIe article with lots of Isopropyl and DeOxit.

The next day, after the main logic board had dried, and on further inspection, I needed to do more spot cleaning on the logic board.   This time I used Isopropyl and  Q-Tips to get in close to each chip.  I was also able to pull out the damaged ROM chip, inspect the socket, and re-bend the pins back into place.  I made a note of the location since this may require further inspection and repair, but at first glance, it looked like that socket had not been damaged, and none of the pins broke off.

At this point, I was able to give the system its first power up, a very exciting moment indeed.  Sadly, there was no video from the machine.  So, this sent me back to looking more closely at the board.  What I noticed was that because there had been so much dirt on the board, there was dirt on the legs of many ICs where they entered into the sockets on the board.  So, as time consuming as this would be, I felt it would be important to pull every IC out of the socket, inspect the IC, clean the legs if needed, and spray De-Oxit into every socket.  Given that there are more than 80 ICs, I divided this task up into a couple of parts.

During this part of the repair, I broke multiple legs off three different ICs.  Again, using another trick I’ve seen from Adrian Black, I was able to solder a small (28ga) solid copper wire back on in place of these legs and get the chips plugged back into their sockets.  I’m super happy that I didn’t have to order any additional chips. (Yet, knock on wood)

On completion of reseating all of the chips on the board, it was time for another power on test.  This time, there was Video, along with the Apple ][  logo at the top and the ] BASIC prompt, a very happy moment indeed!

At this point in the repair there remains a good deal more work to do; the keyboard is non functional, the RAM should be tested, I should add a Floppy Disk controller, but this article has gotten a bit long so I will leave off here for now.

Apple IIe Repair and Use

The Apple IIe was the first computer I spent a significant amount of time working on, because it’s the computer they had at my junior high and high school in rural Wisconsin.  I remember playing Oregon Trail and the original Castle Wolfenstein at school in the school library.  But these were also our workhorse computers that we used to learn BASIC programming and for word processing with AppleWorks.

So, it was with great excitement that I started in watching Adrian Black and various other vintage and retro tech YouTubers dig in on these Apple II computers, learning how they work, how to repair them, and work on cleaning and restoration.  Full schematics are avaliable, and really excellent troubleshooting material from back in the day is also up on the ‘Net.

Because I’m always trying to keep my hobby affordable, I didn’t rush out and buy the first Apple II computer I could find, I made several offers, and was finally able to land a nice-looking example from a family that was cleaning out their basement.  The lot of items for sale included the Apple IIe itself, an Apple Color Monitor, a single Floppy Disk drive, and many floppies and manuals.  I purchased this at the beginning of October, the seller “didn’t know if it works”, so I was prepared for the fact that it probably wouldn’t work.

So after getting the unit home, the first thing I did was to take the power supply out.  The RIFA cap had blow, I could still smell it. I wondered if they had tried to test it and let the smoke out of the cap recently.  I removed the RIFA cap and then tested the Power Supply voltages.  Those checked out good, so I tried to power up the monitor next.  The monitor powered up without incident.  Then, the moment of truth, I powered up the computer (without any cards in it), and it booted right to the BASIC prompt.  A very exciting moment!

After poking around for a few minutes, I realized that some of the keys on the keyboard were not working.  The keyboard was filthy.  It seems likely that this machine had been stored in the previous owners basement, perhaps for decades.  The next order of buisness was to clean the keyboard throughly.  I washed the keycaps, and did what I could to clean the keyboard from the top and bottom with liberal use of Isopropyl Alcohol.  I sprayed a liberal amount of DeOxit into each key and cycled each key a dozen times or more.  This brought back about 1/2 of the non-functioning keys, but there were still three keys that I had to remove.  I was able to take these three key switches (SKCC long stems) apart and clean the removable metal contacts, then replace them in the switch housing.  Try that with a computer that isn’t 30 years old!  This restored all the keys on the keyboard to full function, and it’s been working fine ever since.

The next set of repairs centered around the Floppy Disk drive.  I was excited about getting the Apple Disk II device up and running, there’s something so nostalgic for me about the sound that the Apple II drives make when the computer starts.  When I first received the drive, I heard something rattling around loose inside and so before powering the drive up, I needed to open the drive and determine what that rattling sound was all about.  It turns out that the lever on the bottom left floppy disk guide had broken off.  This lever must remain connected, yet flexible, so I used some strong Gaffers tape to get it back in place so that when a floppy was pushed in, that lever would sense the write protect notch and operate the micro switch inside the drive.  I don’t expect this repair to last forever, but it’s been OK so far.

After this, the Floppy Disk drive did work for some time. After going through about the first 20 disks in the collection, it stopped working, and I plugged in FloppyEmu and was back up and running.  Honestly FloppyEmu is such a great product that I’ll probably keep using it, if it wasn’t for that distinct sound, and wanting to check out the programs on these disks that came  with the computer.  So, eventually I opened the drive back up, an found this on the main drive circuit...

Look at the capacitor on the upper right hand corner.  The right end of the capacitor has completely blown out of the device and there’s literally nothing left inside.  I was able to replace all three electrolytic capacitors with caps that I had in my stock bins, and get the drive back up and running.  I hear that not much else can go wrong with these drives, so I expect this drive to be operating when when the last of the Double Density floppy disks wear out.

So, with the Apple Disk II drive as Drive 1 and the FloppyEmu as Drive 2, I was able to boot off of a disk copy program and copy various disk images back out to Floppy disk.  I was able to make ProDos disks this way, and some games like Flapple Bird.

Along the way I made some simple, silly mistakes, too, like accidentally pushing the color / monochrome button on the front of the monitor, then closing the door and forgetting that setting.  I spent almost an hour trying to figure out why the image was monochrome, then remembered the monitor setting, which I now understand is there to help reduce color fringing with text in 80 column mode.

Anyway, the Apple IIe is up and running and I just couldn’t be any happier with the result, what a classic machine!  It’s been my go to game machine for classics like Donkey Kong and Choplifter since it’s been running.  I’ve also been able to use it in testing a much more broken Apple II Plus machine, but more on that in a future article.

Do you have memories of Apple IIe?  If so let me know in the comments below, or send me an email.

Current State of the Lab Workbench

I thought I'd give a bit of an update about the current state of Steve's Digital Basement, as there have been quite a few upgrades over the last year.  Many of them inspired by Adrian's Digital Basement along with many other retro and vintage tech YouTubers out there.  I really appreciate their willingness to share the wins and the losses.  I share the belief that the more comfortable we can get with learning from failure and not being afraid to try stuff that we aren't good at, the more skilled we will become.  The perfect is truly the enemy of the good.

Since spending more time learning online about the surprisingly high quality of some of the Chinese devices out there, and since I've always wanted a Digital Storage Oscilloscope, I spent some time learning about the various low-cost brands out there.  I often shop the "Open Box" section of the online catalog at my local Microcenter.   They had this Silgent SDS 1052DL+ that sat in the store for quite a while, after the price dropped a second time, I picked it up.  I paid less for it than what I got by selling my old Tektronix analog scope.  I know that the Tek scope is likely to outlast this one, but in the meantime, I've got a really capable scope and I couldn't be any happier with this major upgrade at the bench.

I've also added a new Power Supply recently, it's a generic supply also from China, but has more current capacity than the BK Precision Model 1601.  I'll keep both for situations where I need dual voltages.

The other add from China is a component tester, it’s capable of doing ESR checks on capacitors, and that’s been very useful as I troubleshoot old devices.

The Hakko soldering station was one of my first upgrades when I started to get back into Electronics and repair, it has been a truly amazing tool.  I upgraded from a non-temperature controlled soldering pencil about 5 years back.  I no longer dread soldering, it's an absolute pleasure to use, and the results are significantly better.

In the upper left hand corner, you can see storage bins, I have a couple of sets of these with common electronic components.  I'm not stocked yet to do recaps and other repairs without ordering parts, but I do have some common components on hand, and I've been able to do some spur of the moment repairs without ordering parts, like recapping the control board on an Apple Disk II or recapping the Apple IIe card in my Mac LC.

Not shown in the picture, I have a tool box off to the side filled with hand tools.  This tool box holds; hand tools,  a Multimeter, and various magnifiers.

On the wish list, I'd love to get a really nice stereo microscope.  I previously had a powered Solder removal tool on my list, but I recently got the manual Soldapullt and this has been such a great hand tool that I'm not sure now that I need a powered desoldering gun.  If I start frequently removing ICs and connectors, I may change my mind about that.  I'd also like to get a hot air soldering gun, this would help with desoldering and resoldering Surface Mount components (at this point primarily to help with the ReCapping that I"m already doing).

How to open a Power Macintosh 61XX Series Case Without Breaking It

 Opening a Power Macintosh 6100 is dangerous.  These machines are of such an age that the plastic tabs on the back of the case break off frequently.  Sadly, I've just broken two more this weekend.

That being said, I was successful at opening to cover on one of these computers without breaking the tabs, I was so excited.

In hindsight, I really wish I'd have used my heat gun to soften the tabs a bit before trying to open the case, but I did come up with another hack that I thought might be worth sharing.  (Or maybe I saw this somewhere else and I'm just not remembering where.)

If you do manage to get the case open, you'll see a couple of hooks that face backwards at the back...

One hook just over the power supply, and one over the Expansion Bay.  A quick few minute with the Dremel and you can zip those right off, as shown below...

The cover is now loose, but gravity will hold the cover down, or whatever you put on top, and there's no longer any danger of breaking the tabs on the cover.

Minnesota Computer History - CPT Corporation

Minnesota has alot of computing history.  I've always enjoyed history and technology, and so it's no surprise that I have an interest in the history of technology.  Lately I've enjoyed digging back into that history and discovering a bit more about it as I dig into resources from the Charles Babbage Institute at University of Minnesota.

I started my Engineering Career with a brief stint at Computing Devices International.  This was one of the Control Data companies, which has ties all the way back to the Univac from Remington Rand.  This history is covered well by some interesting talks given here.  This computer company formed just after World War II, and was for quite some time more dominant in the market than IBM.  I hadn't thought much about my time at Computing Devices (now a part of General Dynamics) until my Retro Computing hobby brought me into contact with another piece of Minnesota computer history that I knew nothing about.

I was out purchasing another Macintosh Plus computer as a parts computer for my working Macintosh Plus and I asked the gentleman I was purchasing from if he had any other Retro Computer equipment he'd be willing to sell.  In this case, he did have another computer, and he was wiling to sell it to me.  

The latest member of the collection here is a CPT Corporation Model 9000...

The CPT 9000 is an IBM AT Compatible computer with a 286 processor and 1MB of RAM.  There are several interesting things about this computer, but the one that I've enjoyed the most is that this computer was made in Minnesota.

When I say made in Minnesota, I'm not talking about assembled from board level in Minnesota, I mean that CPT Corporation designed the computer from the component level up in Minnesota.  Here are some pictures I've taken of the boards.  First the CPU Board (This is a single board computer design with a passive backplane)...

You can see CPT Corp. on the Silkscreen.

In reading about this company, they developed high end Word Processing systems, and there appears to be custom hardware on the mainboard to support their proprietary portrait mode, one page at a time display monitor.   My examples does not include this monitor, or any proprietary display driver.

The RAM Board is here...

Also caries the CPT Corp. marks on the silkscreen, as does the Backplane...

The computer case is very heavy and well designed, I believe the Power Supply may be a custom design, as it is mounted as a loose board inside the chassis (no separate enclosure).

This particular computer appears to have been continuously updated till about the mid '90s.  The rest of the components were not made in Minnesota, a plain 16 Bit ISA VGA Card with a Trident Chipset, a working 1.2MB Floppy Drive,  a failed 1.44MB Floppy, a Super IO Card and HDD from the mid nineties.  Perhaps this is the timeframe when CPT Corporation finally closed their doors?

Is this the last computer that CPT Corporation designed and manufactured before their demise?  Is this the last (or only) IBM Compatible PC designed and manufactured in Minnesota?

None of the CPT Corporation software was on the computer, which is not surprising, but I must say I've been a bit disappointed.  I've posted about this on the Vintage Computer Forum here, but there's been alot less interest in the hobbyist community in archiving business software, so no luck locating that yet.  

Also, I have no idea what happened to the Intellectual Property and the remains of the company after the bankruptcy, perhaps the software has been lost to time, which would be a shame given the size of this company at its peak.

Please reach out via email (in my profile), or leave a comment below if you know any of the answers to my questions about CPT Corporation, this computer or the software it ran.  Thanks!