Tandy 2000 Computer Lot - Repaired in 2024

My most recent project has been too repair a large lot of Tandy 2000 computers.  A friend of mine has been collecting these machines for several years and had parts from nine different machines...

We made an agreement that I would work on repairing these machines and we would split the working computers coming out of the repairs but before discussing the repair let's review a bit of history about this machine.  These machines were designed and built by Tandy in 1984.  They run MS-DOS but they are not compatible with the IBM PC like a Compaq computer from that time period.  Tandy had been successful in the computer business since the beginning of the Home Computer era and compatibility had not been a major concern up till that point so they planned to (and succeeded at) building a more powerful computer.  These Tandy machines are unique because they have an 80186 processor and many other differences from IBM PCs and Compatibles.  Here's an ad from the time showing Bill Gates touting the benefits of this machine...

I'm interested in this period of MS-DOS compatible machines that are NOT IBM PC compatible because I think this is a fascinating period between the end of the 8-Bit CP/M machines and the rise of the PC compatible.

Now onto the repair, as you will see these machines were in rough shape.  It turns out that many of the power supplies are no longer working.  I created the following pinout table for the power supply connector going into the motherboard:

Nominal Voltages of Tandy 2000 Power Supply
Pin            Voltage
Orange      +12 V
Grey          5V
Red            5V
Red            5V
Black         Gnd
Black         Gnd
White        -12 V
Blank

Having the pinout and nominal voltages allowed me to go through and sort out the working power supplies.  I think some recapping will be required in the future but for now I do have enough working power supplies to get 3 working computers.

Next, I tested the motherboards.  Many of the logic boards were showing no signs of life with a known good power supply.  The motherboards have 128K RAM soldered on board (4164 DRAMs), and there was a 128K RAM daughtercard that plugged in on the main board itself.  I went through and separated these and tested and got a known good 128K RAM board and cycled through the motherboards, reseating and swapping chips that were socketed and eventually getting about half of the boards working but without doing any board level repair.

The lot also included expansion cards for High Resolution Color Graphics.  These boards require 256K RAM on the motherboard, and they were needed because the only working monitors we had for this lot were the CM-1 Color Monitor.  A couple of the Graphics boards had corrupt video in the color modes, so those were set aside.

The lot also included memory expansion cards that can hold either 128K or 256K on the board.  In the base configuration these machines could have up to 512K total, although later modifications could take them higher.  Thankfully the RAM chips are socketed on these boards, so I was able to take all the RAM off and cycle the 4164 DRAMs through my RAM tester.  After this there was enough working RAM expansion boards to bring the working computers up to 512K.

Next up for repair was the keyboards.  I had one working keyboard which had gotten damaged and had a couple of the keycaps broken off it turns out that was just mechanical damage and I was able to re-assemble and glue plastic parts back together.  The next repairs required me to take the keyboards apart.  One of the symptoms I noticed was that the lights on the Shift and Num Lock keys would come on, indicating that the keyboard had power but then none of the keypresses would work (indicating maybe a bad matrix).  Other keyboards had no power on them at all (which may indicate a bad cable).  I moved the cables around and I was able to get 3 more working keyboards out of the lot.  If needed, the cables can be transplanted into a Tandy 1000 keyboard, but those are getting hard to find, too.

The next order of business was the Floppy Disk drives.  The non-hard drive machines had two drives each and surprisingly most of the drives were in good working order.  I only had to swap around a couple of the drives and I was able to clean them with a normal floppy cleaning disk.  I didn't need to take them apart and lubricate them, although I should.  I was able to prove that both the A and B drives were working by using the disk duplication program called compdupe to create copies of the MS-DOS boot disk.  This machine can be difficult to create disks for because it's a Double Sided / Quad Density drive that can hold 720K.  It works with normal DS/DD media, which I have plenty of, but I still haven't found a way to create disk images, although I understand there are instructions online.

So, this wraps up the repairs, at least for now.  My friend and I split up the machines and we are both very happy to have Tandy 2000s in our collection, here's mine...

There's still a bit of extra material coming out of the repair, hopefully enough to make another working machine.  This material been offered to another Vintage Computer collector so perhaps the repair project will continue.  In the future, I have a couple of upgrades I'd like to do on the Tandy 2000s.  I'd like to figure out how to get the Hard Drive working again on the Hard Drive machine or get it working with an MFM Emulator.  I'd also like to see if I can replace one of the physical floppy drives with a Go-Tek.  This would make it much easier to work with the odd floppy format as there is quite abit of software avaliable for the machine online.  But for now I'm glad to have the project completed and move on to to the next Vintage Computer project.

Do you have memories of the Tandy 2000?  If so please feel free to reach out in the comments or send me an email, my address is posted in my Blogger profile.

My Visit to Cray Research and Paying it Forward with STEM

I'm a lifelong learner and invested in helping other people learn about technology.  It's one of my motivations for this blog.  I recently had a reminder of one of the many people who have helped me along the way.  As I was sorting and organizing some of my old letters I found this business card from an engineer at Cray Research.  This person spent an hour with me when I was job-shadowing as a High School kid.  I don't have permission to share his information, so I'll blur out his name, but in 1991 or 1992 Cray Research cards looked like this...

I grew up in a small town in rural Wisconsin called Elk Mound.  It is about 20 miles west from Chippewa Falls where Seymour Cray was from.  Cray was in Minnesota for Engineering school and the beginning of his career but after he was established he set up Cray Research back in Chippewa Falls in the 1980s.  When I was a kid my high-school guidance counselor knew that I was interested in technology and he arranged for my friend and I to spend a day at Cray Research in Chippewa Falls.  There was a general awareness in the community that Cray made super computers but I was not very informed about computing at the time so I didn't realize the importance of Seymour Cray, or what a cutting edge company Cray Research was.  The visit did make a big impression on me and helped confirm for me that I wanted to be involved in engineering of some kind.

Seymour moved to Colorado Springs in 1989 so I can not claim that I was even in the same building with him but from what I hear he was a very quiet person and would have probably avoided a tour group anyways.  But I did meet an engineer who made an impression, the same engineer whose business card I found just last year. Using LinkedIn, I was able to reconnect with that engineer.  He's retired now and he didn't remember our visit, which is understandable since it's a distant memory for me as well, but I still had the opportunity to thank him.

I pursued engineering and my first job out of college was working at one of the Control Data successor companies.  One of my favorite memories from my short stint at that company was sitting with some of the older engineers in the lunch room and hearing stories about the early days of computing.  I remember being amazed at hearing for the first time how they had memorized the Op Codes for the computers they were working on.  Again, I didn't have the context that I have now, but having built a PDP-8 replica and learned a bit more about it I realize that this was not bragging.  The machine had no boot ROM so it was mandatory to toggle in the simple loader program if the computer memory was reset.  It was so common and important that DEC had it printed on the front panel of the machine.

But, I soon moved on from the Control Data company to the field of Factory Automation which I have been working in ever since.  That first job was the last of my loose connections with Seymour Cray and the Cray companies. But I remain committed to the idea of paying it forward, and I continue to welcome opportunities to give young people tours of my workplace.  It's exciting to think about where technology will be when these younger folks are my age or retired like the engineer at Cray who spent an hour with me 30 years ago.

Do you have any memories of Cray or the Cray companies?  Please leave a comment or feel free to reach out via my email address in my complete profile.

Apple II Plus - Trash to Treasure - Part III - The End?

I haven't given an update on my Bell and Howell Apple II Plus machine since 2020.  I have done several little upgrades on that machine which have combined to produce an amazing looking machine.  This year at VCF Midwest I got to talk to the owner of MacEffects, thank him, and show him a picture of the machine. Later I realized that I haven't posted about this machine here on the bLog.

Since I last blogged about this machine, I asked around about which color monitor would pair with the machine.  I realize that most Apple II machines of this era would have been paired with Black and White monitors, but I was holding out for a Color monitor that existed at the time.  It turns out that the Sony PVM line does go back to the 80s.  I didn't find a period correct PVM but I was able to buy one that is the right size to sit on top with the floppy drive next too it.

I also added the Language Card to get the machine up to 64K, and a Microsoft Z80 card so I can run CP/M on this machine.  I made some wiring repairs in the backpack for the power supply so it would be more reliable.  I make a joystick adapter to go from the DIP style connector to a 9-pin connector so that I can plug in Apple IIe style peripherals to this machine.

But the most dramatic changes are cosmetic.  After having an eBay saved search running for several years an Apple II Plus Top Cover came up.  I had seen one a couple years back and I took a pass on it, but I'd been regretting that decision so I jumped on this top cover.  Since it was for an Apple II Plus, the badge and color was wrong but as I have alluded too MacEffects is producing reproduction badges.  So with a bit of paint for the top cover and a new badge, it looks like a Bell and Howell top cover.

Knowing that I would have the computer looking amazing, and seeing that MacEffects also has case badges for the Floppy Drives, I purchased one of these as well.  Taking the drive apart to repaint the housing was pretty straightforward.

After a bit of repainting my barn find Bell & Howell Apple II Plus looks better than I ever could have hoped given the state the machine was in at the start...

During VCF Midwest I talked to another owner of one of these machines and through conversation with him and with other folks I learned that mine is one of the earlier machines.  It has the sought after Backpack (although the audio section of mine is not working) and it has keyboard keys that are more smooth.  Apparently Apple switched keyboard vendors later in the product run.

I'm super happy to have this machine in the collection and grateful to the community for the help, advice, and new parts that I needed in order to get this machine back to where it is now.  It's certainly in my top ten favorite machines in my collection.

Vintage Computer Festival Midwest 2024 Recap

Vintage Computer Festival Midwest 2024 is in the Review Mirror.  I was happy to be there for my third in-person visit, and my second time as an exhibitor.  This year I had a busy summer, so I wanted to show a display that was easier to setup with no large projects required in order to prepare a hands on exhibit.  So I decided on the topic of "Laptop Evolution: 1988 to 1999".  I prepared 8 laptops to bring down and show off, but because of demo gremlins, I ended up with 6 working computers, then when the Mac Portable's HDD died, I was down to 5 computers on the demo table.

This year for the first time some of my family members expressed interest in tagging along for the roadtrip to Chicago and this made the event more fun for me.  One of my daughters is selling Retro-Computer themed art made out of e-waste.  She almost sold out at the show, but a few items are left on her etsy shop here...
Burbots

Here is what the booth setup looked like...

From left to right on the top of the table; my daughters art, then my interactive display.  Down below on the floor I setup computers that I'd repaired and that were for sale.  I only brought home 3 of the 9 computers I brought to sell, so I was quite happy with that result.

So far the only coverage I've seen online of the event that showed my booth was this video from Chris DeHut.  Chris is absolutely right about the screens, I wanted folks to experience how great the keyboards where and how poor the screens were.  Everyone knows about Moore's law and those of us who are old enough remember when our computers were doubling in speed every time we replaced them but there were a few cool things about the old hardware, including the amazing keyboards and the creative form factors that we used to have before all laptops started looking the same.

I unloaded about 8 parts machines or project machines onto the Free Pile.  This year the Free Pile was a happening place and I don't think anything that I put out there sat for more than a few hours.  The only thing I got off the free pile was a diskette holder for 5 1/4" disks, but since one of my goals for the event was to come home with less material than I left with, I was OK with that.

The only complete "new to me" computer that I brought home was a Sun Ultra 5 machine that I had been offered by a generous donor who is downsizing their collection.  I'm very happy to have this machine and it comes with a special surprise, but I will save that for a future bLog article.

As always, the highlight of the festival is the conversations.  I had many conversations with people I already knew from here in Minnesota or from YouTube but I also met many interesting people, some of who walked into the show because they were in the hotel for a different conference.  I heard many interesting stories from people about their experiences with computers and that is really what makes the show so much fun.  Here's a few of the stickers and cards that I collected, my daughter had an even larger collection...

The new show venue was excellent.  It was so much less stressful not having to worry about the power situation and having space for people to stand and talk and also move around instead of being crapped into tight aisles.  This also helps with the interactive exhibits because people don't feel like they had to move on immediately if they don't want too.  The hotel rooms were a bit more expensive, but I feel that the venue was so much nicer that it was a small price to pay and I would be happy if the organizers could get us back into the same venue next year.

Thanks so much too the organizers of the VCF Midwest event, your efforts are very much appreciated!  This event remains the highlight of the year for me in the retro computing hobby, and the people and ideas that I see at the show will inspire projects and conversations that will continue throughout the year.

My IBM RS/6000 Power PC AIX Unix Machine

As readers of my bLog will no doubt know, I'm a big fan of the Vintage Computer Federation Forums.  The community there has helped me with several projects that I would not have been able to complete on my own. I recently saw a post from a gentleman who had listed four different Unix workstations.  I reached out, and he generously agreed to pass on an IBM RS/6000 machine, a big thanks to Peter M. for this machine.

First things first, Peter let me know that there were a couple different versions of IBM AIX which were not yet archived including the first version of AIX that can run on this box, IBM AIX 4.3.3, and also IBM AIX 5L V5.1, so those are online now for anyone else who may need them.  There are earlier and later versions of AIX already archived, and there's still quite a bit of software avaliable online including a person who is building GNU tools for the OS.

This machine is a Power3 computer.  It's a single core PowerPC based processor from about year 2000.  Specifically, this is a 44P Model 170 at 333MHz, 1MB L2 Cache and with 512MB RAM.  This machine was assembled in the USA at the IBM manufacturing facility in the Rochester, MN factory.  I've been in that facility many years ago so this machine is a part of Minnesota Computer History.

It was reported that the machine had not been used for several years and so as usual I started in with a light dusting and cleaning.  I didn't have to take the machine far apart but I had been warned that the CPU daughter card would come loose and prevent the machine from starting, so I addressed that right away.  The RAM also needed to be re-seated, the battery reinstalled, and the GPU reinstalled.  Thankfully, all the hardware manuals for this machine are still online at the fantastic IBMFiles.com website, so getting through the error codes on the front panel was pretty straightforward.  If the machine stops booting it's quite easy to look up the error codes where it got hung up, much like the POST codes on a PC.

It was interesting to install the oldest version of the OS that would run on this machine, version 4.3.3, so I did that and looked around a bit at that but eventually I decided that the last version would be more useful, so I went looking for AIX version 5.3, and was able to find disk images for that online.  I burned the 8 CD set and started the install upgrading over the top of a 5.1 install.  That worked quite well and the machine is up and running with networking...

I'm happy to have the machine cleaned up reloaded and up and running.  This completes the first phase of work on this machine, but I look forward to spending more time getting software tools loaded onto the machine, doing some more networking with it, and learning more about this era of AIX.

If you have one of these machines, or any stories to share please feel free to comment below, or drop me an email, my email address is in my profile.

Compaq Portable III Restoration

 One of my contacts at Free Geek recently reached out, he had a computer that had been on my wish list for a while, a Compaq Portable III.  I already have a Compaq Portable I (which also was a project computer from Free Geek) and Compaq Portable II, and I really like these early Compaq machines because of the story of the company.  If you haven't read about it, I recommend Rod Canion's book "Open".

Anyway, this repair story starts with a water damaged Compaq Portable III.  It was quite dirty and since I'd been told it was water damaged I had quite low expectations, purchasing it as a parts machine for a future repair.  When I got it home, I immediately got started with cleaning since it was so dirty I didn't even want to touch it.  Here's a picture from "Before"...

Definitely too gross to work on.  After cleaning for a while I started to take the machine apart.  I was pleasantly surprised.  The machine was very dirty and dusty inside as well, but there were no signs of water inside.

The next step was a Power On test. I could hear some clicking from the Power Supply, but no fans, no backlight from the display or any other signs of life.  Then, there was a snapping sound and smoke!  I suspected a capacitor.  Testing with the machine off, there was a short on the 5 Volt power rail, which for this era of machines often indicates a bad Tantalum capacitor.  I was able to find the blow tantalum and replace it, and as soon as that was done the machine booted.  I was glad to see that the Plasma Display appears to be intact as this is the unique new feature that really sets this machine apart from the Compaq Portable II which still had a CRT, and the next generation from Compaq which had a more normal LCD display.

The system had the following errors, Keyboard Error, Disk Controller Error, and Time of Day / Clock Error.  The keyboard error and Disk Controller Errors were easy to resolve because these peripherals were simple disconnected.  I cleaned the 1.2MB 5 1/4" Floppy disk drive with a cleaning floppy and I was able to boot the machine from a DOS disk.

I also discovered that the Hard Disk in the unit had been disconnected.  When that was reconnected, I discovered that the disk was blank with only a few DOS files left on the machine.  I tried re-installing a newer DOS, but I was not able too do so, there are write errors when formating the drive, so I'm disconnecting it and replacing it with an SD to IDE adapter solution that I've used in some other vintage machines.  Based on this other helpful bLog article, I set the system up for a Type 42 hard drive which provides just over 500 MB of disk space for this machine on a 1 GB SD card.

Fixing the clock error proved to be the most difficult part of this repair.  This is important for these early Compaq machines because they do not have the BIOS setup program in ROM, you have to boot up from the Compaq diagnostics floppy every time the computer looses power and that make the machine alot less usable.  Apparently there were two different clock circuit options for the 286 version of this machine.  One option is the Dallas Clock chip, which are still being made today, but that is not the option this machine had.  This machine has a rechargeable battery which had been removed from this computer probably due to concerns about leakage.  I tried jury rigging a battery holder for a CR2032 battery into this space where the rechargeable battery was but I made an error in connecting that and my modifications were a failure.  After doing some more research online I found this fantastic article on MinusZeroDegrees.net.  This article contains enough detail that I thought I would try to switch my board over from the unobtanium battery pack too the Dallas clock chip circuit configuration.  I was able to make those modifications, and now I have a working battery backed up clock and drive settings!

I installed MS-DOS 6.22 on this machine, and copied many of my commonly used utilities over to the machine.  That wraps up the repairs on the Compaq Portable III for now.  It needs a bit more cleaning, and perhaps some day I'll find a RAM expansion for it, but for now I'm quite happy to have one of these in the collection.

Please reach out in the comments or via email (My email address is on my profile) if you have any thoughts about the Compaq Portables.

Trash to Treasure - Osbourne 1a Computer

 The Osbourne One is widely regarded as the first portable computer.  It was released in 1981, and although it didn't include a battery, it was advertized that it could fit under the seat of an airplane.  I have a soft spot for CP/M machines and so I've had the Osbourne 1 on my wish list for a couple of years.

Last year my friend Steve gave me a "fixer upper" Osbourne Executive.  That was an interesting machine, too, and this example was is really good cosmetic shape.  I spent quite a few hours restoring the machine, working on the CRT alignment, cleaning and lubricating the floppy disk drives, making boot media, and troubleshooting the main board.  But ultimately, I was not able to get it booting.  I isolated the fault to the main logic board, I think there is something wrong with the floppy disk controller because the machine can move the drive heads and step to tracks, but when it starts to boot, it reads in track zero, steps the head to the next track, then stops responding.  The machine behaves the same way with a Go-Tek drive emulator, so that's why I'm pretty sure the fault lies with the main logic board.  So I had put that repair on hold and was going to come back too it.

However, a more interesting option presented itself a couple of weeks ago.  I was shopping at Free Geek Twin Cities as I often do and they mentioned that an Osbourne had just come in.  It was in really rough shape, quite yellowed, and keys missing from the keyboard, but it appeared to be booting and asking for a boot floppy.  It wouldn't boot from the disk that had been left in the drive, but in my experience almost all of these drives from the early 80s need cleaning and lubrication before they can work correctly.  So, they offered me a good price on the Osbourne as a project machine and I purchased it...

The first order of business on a restoration like this was for me to get the machine booting.  I started by making some "known good" boot disks using my SuperCard Pro disk imaging setup.  I think I've covered this workflow before, but my current workflow for making boot disks for new to me machines is to find disk iamges on Dave Dunfield's site here.  I then use the fantastic tool HxE Floppy Emulator Software to convert the IMD disk image format to the SCP flux format used by my disk imaging hardware.  Then, I use the SuperCard Pro to write out the disks to hardware.

One hack that I've learned on the hardware side with these CP/M Machines is that since they must boot off Drive A it will have alot more wear and tear on it.  It makes sense to swap Drive A and Drive B as well as service both drives.  In this case, the drives mechanisms were from two different vendors but the control boards were the same.  The Osbourne 1 has power going to the floppy drive over the ribbon cables, this was not the case for the Osbourne Executive.  It turns out that all you need to do to tell which drive is the A drive is swap the termination resistor, there are no other jumpers on the drive controller board, after this the machine was booting!

Once I got the machine booting, it was time to swap over the external case parts from the Executive.  This article explains the differences between the very early Osbourne One computers and the 1a model that I have here.  I was quite fortunate to have purchased the 1a, not realizing at the time, but the case is exactly the same shape as the Osbourne Executive.  The front bezels are unique, so I cleaned up the front bezel of the Osbourne One with soapy water.  The Executive had a bulge under the handle in order to accommodate a fan, but many people feel the machine should have had a fan so I'm happy to have that as part of my Osbourne One even if it's a slight anachronism.

Another surprising item was that although the keyboards look identical and have the same connector they do not appear to be compatible with one another (I guess the analogy would be the XT and AT keyboards with the same connector but different scan codes). So, I removed all the yellowed keycaps from the Osbourne 1 computer and swapped the keyboard over into the Executive Housing.

The machine turned out lovely, I'm very happy with how it looks...

From the sides it is even more of a contrast as the old case was badly yellowed.

I'm glad to have the machine booting and running, but I would also like to add a Go-Tek with Flash-Floppy firmware.  I'm not quite sure how to do that with the non standard drive wiring on the Osbourne One, but that will be a project for another day.

Hackers and the PiPD-10

I've previously written about using simulation and buying replica kits as a more attainable way of getting hands-on time with retro computers that are rare.  This article is two years old (as of this writing), and since then I've built another PPD-8 like system and Oscar Vermeulen's PiPD-11 (in Mid 2023).  I still think these kits are a great way to learn about old systems.  The learning continues with Oscars newest kit, the PiPD-10.

As soon as I heard about the PiDP-10 project I was excited.  I've known something of the original Hacker culture since reading the Jargon file online in the early 2000s and I've had a copy of the "New Hackers Dictionary" since then.  My college, the Milwaukee School of Engineering had Digital Equipment Corporation VAX machines when I was there in the 1990s.  I'm sure that without being conscious of it I was exposed too and adopted a midwestern version of Hacker culture as it existed there in the late 1990s.  

I've been anticipating Oscar's new machine for quite a while.  During the wait I read Steven Levy's book "Hackers".  This is a book that describes longer periods of the history of computing, but it has chapters focused on the people and the culture of the MIT AI Lab in the early days of computing in the 1960s that I had not read much about before.  This is the time period of the PDP10.  Even though the ITS system did not become prominent and is not a direct predecessor to the Operating Systems of today, so many of the people who worked on it and the ideas behind it have been incorporated into today's software.

But enough background and back to modern times.  I got into the PiDP10 Google Group for conversation about PiDP-10 and I asked to be added to Oscar's "expression of interest" list as soon as the Beta test period ended.  My PiDP10 Kit arrived in mid April 2024.  I build the kit on the first weekend after it arrived.  The build went pretty well.  The biggest challenge that I had was damage around a trace that I caused by not being careful with a component, but once I repaired the broken trace all the LEDs worked as expected.  It was a long build but well documented as usual for one of Oscars kits.  The PiPD10 looks great and since it has some graphical elements I'm going to keep it in a place of honor on the shelf above my desk where I can also keep it plugged into a Monitor, Keyboard, and Mouse...

The next step for me after building the kit was a challenge.  Not knowing anything about ITS I really needed the manual to make progress.  At one point I'd thought the system wasn't coming up because I'd corrupted the file systems so I re-installed a fresh image on the Pi and went through the entire install procedure again,  But that was not the root issue, I just didn't know how to bring up ITS.

Oscar published a draft version of the manual in the PiDP10 Google Group shortly after my kit was built and with that I was able to bring up ITS on the simulated hardware and begin a bit of happy hacking!  I haven't had much time with the system yet, but having it convenient at my desk will make it easy to go back and explore what it was like to use a computer back in an era when having computer access was not a part of normal life for people.  I'm looking forward to that!

Let me know in the comments, or send an email if you have memories or a connection to Hacker culture.  Also let me know if you have suggested about the ITS or TOPS operating systems and things that I should try on the PiPD10.  Thanks!

A Tandy 4000 Computer Repair

Adrian Black recently posted a video about a Tandy 4000 computer, an early 386 machine.  I was excited to see this because (as he has mentioned in his video) you don't see alot about these machines online and I have one.  One of the commenters on his video said that these are rare because the machine was only sold through the specialized Tandy computer stores and not at regular Radio Shack stores like the Tandy 1000 range was.

My Tandy 4000 came from another collector here in town last year.  He sold me the machine (at a very good price) because he knew that it had some blown capacitors and that I enjoy doing repairs. I hadn't blogged about it at the time because this was a somewhat routine repair, but if there is interest from Adrian's video I thought I should share my repair experience.

When I got the machine home and began troubleshooting I was able to identify a couple of bad Tantalum Capacitors (which was also a problem on Adrian's machine).  After I replaced those, the motherboard worked!  However, when I plugged everything in again, it stopped working, it turns out the Seagate ST-251 drive in my machine did not work, it kept the machine from powering up.  It's possible this drive also has some blown capacitors.  Thankfully at this point I had a spare ST-251 that I'd repaired after another project ended.  I was able to install that ST-251 into this machine and set the failed one aside.

The next challenge was a cosmetic one.  The faceplate / bezel of the 3 1/2" drive was broken off from my machine and it was nowhere to be found.  I removed the drive that came with the Tandy and replaced it with a beige 1.44 MB drive and bezel kit from Free Geek Twin Cities.  It looks quite nice, if maybe not quite exactly right...

I was not able to find the correct settings for the EGA card in the machine and the display was showing odd color artifacts so I ended up installing a VGA card.  I was also able to upgrade the RAM to 8MB which would have been a very expensive upgrade in 1988.

As with many early systems the BIOS setup program for this machine is not in ROM.  I tried GSETUP as I already have that on a boot disk but that didn't work.  I was able to find the Tandy 4000 specific setup program online here.  I created a DOS 5 boot disk with it and I'll be keeping that with this machine.  I used the Tandy setup program to set the drive type to 39 for the ST-251.  Another quirk was that I had to manually enter the RAM size, as 7168, the setup program did not pick up the RAM amount automatically.  Odd, but it works and boots without any faults.

I'm happy with how this repair turned out and glad to have this machine as a part of my collection!