Project Updates - Dealing with the Backlog

It's been a busy year for me and so I haven't got as much retro computing done this year.  That being said, I have been able to sell four computers and give away a couple more this year so I am still having success with thinning out the collection.  For quite a few years I've been building a backlog of interesting broken machines.  I keep this hardware out in the garage and have a document going for each of these potential projects.  When I'm feeling inspired to take on a new project I can go fine one any time by looking at that folder and see what I'm interested in taking on next.  I've had a bit more time as of late and I've repaired a series of PCs that I'll describe in this article.

The first repair is an interesting Zenith 386 PC that came from Free Geek Twin Cities in the spring of last year.  This machine was badly rusted from water damage in and around the power supply.  The Free Geek team handled this machine well, they knew that it should be powered up, but the machine included a nice matching keyboard and a full box of documentation and software so it was worth some effort to fix it up.  

I started right in on this machine last year.  I took the machine all apart and cleaned it up.  It's model number ZBF-3340-EK, an early 386 machine built on a passive backplane.  The backplane is based on ISA but extended to 32 bits.  It was a very good thing that Free Geek didn't power the machine up because there were pieces of rust floating loose inside the power supply.  I took all the metal pieces apart and cleaned them up. I spray painted to the rusty pieces to stop further rust, but this wasn't a full restoration, just trying to halt the deterioration enough to get some basic testing done and decide if the PC would be salvageable or not.  To my great surprise after cleaning up the machine and some basic repairs, the PC was able to Post and I got video working with an old VGA card which had been paired with the machine later in life (It originally had a proprietary monitor and video card).  It took quite a few hours of effort to reach this point so I set the project aside.  I thought I'd come back to it soon but it ended up being a year till I came back to it.

After moving this PC around in the garage for the 3rd or 4th time I decided it was time to finish this project.  I took the machine apart enough to get a look at the four drives.  It had two 1.2MB 5 1/4" Floppy Disk Drives, and two Full Height MFM Hard Drives.  I cleaned and tested both of the Floppy Drives.  One of them was working and the other was not.  I replaced the non-working drive with a 3 1/2" drive I had in my spares, and set the 5 1/4" drive aside for future repairs.  Once I figured out the BIOS settings which were needed for the two Hard Drives, I was happy to see that both of them worked (after a few seek errors, which makes alot of sense if the heads had not moved for a decade or more).  It's very cool to have a machine with Dual MFM drives, although I may just leave one in there and keep the second one for another machine.

Adding a clock battery was the final step.  After adding the clock battery the PC still wasn't holding time and BIOS settings.  It turns out there was a bit more corrosion on the board around the battery area so I replaced a few corroded components, some diodes and resistors, and I added a bodge wire for a damaged trace.  After that the clock battery worked and it is holding the BIOS settings.  The machine looks nice...

Due to the solid construction, large chassis, and dual full heigh MFM drives, this computer is very heavy, and it's great to have the documentation and a matching keyboard with lovely mechanical switches.

The next PC up on the bench is an XT class machine.  The seller let me know that it had bad tantalum capacitors which had blown.  They didn't want to do a recap on the machine so they sold it on to me.  This is machine sat on my project intake queue for even longer than the Zenith.  I have quite a few XT PCs so I knew this would be a PC that I wouldn't hold onto for my collection.  It turns out that it had one bad tantalum (which failed short on the +12 volt rail), when I removed that, the computer came up to the BIOS Post screen.  After a few minutes of operation, another tantalum failed (this time on the -12 volt rail), but again that was easily removed after some basic troubleshooting probing around with the multimeter on the board.  I didn't have 4.7 uF Tantalums in stock so I ordered some of those and did the recap when those arrived.

Other than that, my main tasks were to take the machine all apart and clean it.  It was quite dusty.  I cleaned the mainboard with my ultrasonic cleaner.  After it dried I cleaned and tested the 360K 5 1/4" Floppy Disk Drive.  It was working good.  Sadly, the MFM hard drive inside the machine was not working.  I set that aside for further troubleshooting.  The faceplates for this machine were incomplete.  I was able to find a second half-height black Floppy Disk Drive to cover the gap in the front panel of the machine, and I also 3D printed a Full-Height Hard Drive blanking plate for the other drive bay, which completes the cosmetics of the front panel.  The machine is fully functional, and I'm happy with how it looks...

The last PC in this group was an original PC, the IBM 5150.  As readers of the Blog may know, I already have one IBM 5150 that came from a pickup of Facebook Marketplace some years back.  But over the last couple of years I've been making an effort to find a second machine if I can find one at a good price.  I'd been collecting bits and pieces for a second IBM PC for well over a year now and I finally came back to this project since I was already working on the XT Clone from that era.

The IBM PC also had bad tantalums on the main board and that was the reason why the seller sold it to me.  I was able to locate the shorted capacitor and replace it.  I also tested the power supply with a load but disconnected from the PC, the power supply voltages were all in range.  I was able to find a VGA card that would work in an 8-bit slot.  This enabled me to do testing with a more modern monitor and I also left the original Monochrome MDA card in the machine as well, since the IBM PC does support two different types of video cards at the same time.  The machine has 256K of memory (the maximum capacity on that mainboard) and it Posts and comes up as expected.  The next order of business was to clean the two floppy disk drives.  After cleaning they were both working.  I had two cases and so I was able to put together the best cosmetic version of the case.  It's got some rust spots on the top, but as a spare machine it will be just fine and I'm happy to have it in the collection...

Of these three machines, I'll be moving the first two on too new owners, either here locally or at VCF Midwest in the fall.  The IBM PC 5150 will go back into storage to be used as a spare.  Given how long it took me to get to these repairs I probably won't be seeking out more machines of this type to repair, but it is always gratifying to get a broken computer fixed and to have more projects off my to-do list.

If you have any memories of using a Zenith 386, an Ameridata XT PC, or an IBM 5150, please post in the comments below or drop me an email (my email address is in my profile).

Retro Computing at the Movies

Streaming and the wide availability of video on the Internet have made it easier than ever to find and watch material that was unavailable or just hard to find for many years. I a previous bLog article, I covered YouTube channels that are providing archival first person computer history videos.  But Hollywood entertainment is another culturally relavant source.  Here are several feature length Hollywood movies with connections to computing and computer history.

The films in this article fall into two categories.  The first set of films from before Y2K show peoples attitudes towards computing machines and their interactions with them.  The second group of films are more modern movies post Y2K which have historical computing as a theme of the movie.

Older Films (Pre Y2K)

Desk Set (1957) with Spencer Tracy and Katherine Hepburn was fun, I saw this film for the first time last year.  Two of the things that stood out to me were the uncertainties the workers had about how computer automation would affect their jobs and a repetition of the pattern where new automation solutions do not live up to the hype, at least in the short term.  An enjoyable film and one I'd recommend.

The films Twilight's Last Gleaming (1977) and Damnation Alley (1977)  both show inside of a Cold-War Atlas missile silo.  These were of interest to me since I'm a child of the cold war and the "What If" scenarios presented by these movies are definitely the main point.  But another thing caught my eye watching these films since these missile silos were controlled by a massive computer network called the SAGE Air Defense System (or its successor).  SAGE was designed and built during the cold war to try to prevent nuclear strikes from the USSR reaching the US.  If you are not familiar with the SAGE system, there's a fantastic talk from VCF 2025 that I'd recommend by Richard Thompson "The SAGE Air Defense System".  Richard points out in his talk that many of the SAGE control panels were saved and used a props in TV and film decades.  These appearance are cataloged on Mike Loewen's website here, and his catalog opens another whole world of media exploration in Film and TV shows.

What list of computer related films would be complete without a discussion of War Games (1983)?  This is the first film on my list that I remember watching at the time.  Back then I was more concerned about the threat of war but I was also interested in computers and computing.  Here's an interesting article about the tech used for making the film both on and off screen.  The main computer star of the show is the IMSAI 8080 computer, which has become quite expensive.  These pre-1977 machines didn't sell in the millions like an Apple II, but we can still have a similar experience with a modern replica kit built using a modern microcontroller.  I've got one of these kits on order, so stay tuned for a future bLog article on that topic.

Skipping ahead more than a decade, we have Hackers (1995).  I was in college at the time struggling to get an engineering degree and surrounded by computer geeks like me.  I didn't have a car in college and I didn't get out to the movies much which is just as well because we would not have found much to relate too in this film.  We weren't cool like the characters in the film.  It wasn't until studying the history of the Homebrew Computer Club and Hacker culture that I began to understand how computing was connected with the 60s counter culture on the West Coast.  This was not a significant part of my experience at a midwestern engineering school in the mid '90s.  However, rewatching the film recently was a fun opportunity for me to play the "Name that Computer" game.  Trying to figure out, is that an Apple PowerBook?  Is that a Toshiba Satellite or a Tecra? Which one?  I don't have a list from my last watch through.  Google search shows a detailed list, but I'm honestly not sure if you can tell just from shots in the film which computer is which, so I won't link that spoiler article here and let it ruin the fun of re-watching the film and playing "Name that Computer".

The only romantic comedy on todays list is You've got Mail (1998).  I recently rewatched the film as I was interested in seeing the portrayals of the early days of the Internet, but I'd forgotten (or never noticed when I was a kid) how problematic the Tom Hanks character's behavior (Joe) is.  But I watched the film so you don't have to.  Per the fantastic FAQ section on IMDB, Joe is using a "Desktop Replacment" IBM Thinkpad 770 and Kathleen is using an Apple Powerbook G3 250, the fastest of the Wallstreet machines.  I did enjoy the nostalgia remembering using the AOL free trial period and other dial up Internet experiences back in the day.

New Movies (Post Y2K)

The second category of films on this list is modern movie set back in time with computer themes.  When we look at modern films about the past sometimes we may learn more about our present attitudes than we do about the past, but these films are still interesting.

The next movie on my list is The Imitation Game (2014).  This is a film about Alan Turing and his team's work during WWII on code breaking.  I had my own doubts about the historical accuracy of this film after watching it.  One reviewer confirmed my suspicions says this is "... one of the most celebrated and most misleading historical movies ever".  I think most of us interested in computer history would be better off reading this article and skipping the film.

Silicon Cowboys (2016) was intriguing to me.  I've read and enjoyed Rod Canion's book "Open" about the founding of Compaq but I really didn't get into the TV Series "Halt and Catch Fire".  I remember one of the folks presenting about the history of Tandy computer saying "it was never that exciting" or something to that effect about that show.  But Silicon Cowboys is focused on what actually happened and that's still very exciting.

I've seeen The Social Network (2010) but it didn't make that big of an impression on me, so I'm not going to comment other than to say that I did watch it.  Hidden Figures (2016) is a feel-good movie where the underdogs overcome their challenges because of their patience and hard work.

What other films can you think of that have computing as a theme of the film?  Comment below or drop me an email, my address is in my blog Profile on the left side of the homepage.

Epson QX-10 - One of the Last CP/M Machines

The Epson QX-10 is a sleek looking design from the early 80's.  It is from the tail end of the CP/M Era and it's a really neat looking machine.  My experience with the QX-10 started when a friend was demonstrating his at a local Retro meet up hosted by Free Geek.  It turns out he had a second machine in need of repair and since he's already got a very nice one, I was able to acquire that second machine from him, thanks again, Steve!

I started working on this in the Fall of 2025 when I acquired the machine.  There was no cable included to attach the custom CRT to the base unit.  This cable brings both power and signals from the base unit to the CRT and so it's difficult to begin testing without that.  There is a replacement cable avaliable online, so I ordered one of those.  With the cable installed I could see that the machine was powering up to the "Insert Diskette" prompt.  This is a very good sign because it means that the processor is running and whatever diagnostic checks are built into the ROM are passing.

As with most CP/M machines that don't have a hard drive the A drive is used constantly to boot and run the machine, so the A drive often needs special attention.  This machine was no exception.  The floppy drives were manufactured by Epson themselves.  In order to maintain the sleek form factor of the machine they made these drives 1/3 height, not a standard 1/2 heigh drive, so these can not be easily replaced.  Knowing this I took my time removing the drives and cleaning and lubricating the mechanisms.  They were so jammed that I could not even insert or remove floppy disks from the mechanism.  With the floppy drives working, I could move on to the next phase of the repairs.

I made some floppy boot disks using my flux disk imaging setup that I've discussed before, but unfortunately my normal workflow did not work because these machines have a very unusual disk geometry so the first round of disks I created were not able to boot the machine properly.  But I did get far enough to type characters in to the screen and this is when I noticed the next challenge, the keyboard was not working.

This keyboard, the Epson Q603A, is a special one designed for the word processing software called ValDocs.  There is some good information on Deskthority about the keyboard.  This is a foam and foil keyboard, so I was not concerned because I've repaired several foam and foil boards over the years using the replacement kit from TexElec.  However, sadly, this board used a prototype switch with a much lower profile of foam and the normal replacement pads would cause the switches to remain pressed all the time.  I emailed TexElec about this and I was very happy to learn that they were already working on a low profile foam pad.  I got a set of these and installed them and the keyboard is working again as expected, one more step closer to getting this machine back on the road.

At this point because of my problems getting booted up and not have known good boot disks I stalled out on the project and set it aside.  But within a few weeks I saw a relevant post on the Vintage Computer Federation forums where I hang out, so I chimed in on there.  I received some great feedback about my disk imaging problem from one of the members there and I was able to create some new boot disks using a different starting point.  These boot disks worked and I could see that the Epson was fully booting up into an operating system.

Unfortunately, as often happens with Retro Computers, just when we think a project is ending, something else broke.  The CRT display starting rolling and I couldn't get the video to stabilize.  This CRT has only one adjustment for brightness on the outside so I took the case off to get inside.  I went through all the potentiometers on the circuit board and put Deoxit Fader Lube on them and cycled them back and forth.  I also did a careful inspection.  I was not able to identify anything wrong. After plugging everything back in it started working again.  I think there may be an intermittent connection with one of the sync signals so I'm going to try to isolate that to the Monitor side or the Computer side and maybe reflow the solder joints on those circuit boards.

But for now, the machine boots and runs, and it's time for me to explore one of the last and most modern looking of the CP/M machines.  I'm really glad to have this machine in the collection as it very much has the look of the era it came from...

Did you use CP/M back in the day?  Do you have memories of the Epson QX-10 or the Valdocs software?  If so leave a comment below, or drop me an email at my address in my profile, I'd love to hear about your experiences.