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!

A Kaypro II from 1982

My latested repair story is about a Kaypro II from 1982.  The Kaypro machines have such an odd numbering scheme.  They used Arabic numerals and Roman numerals to refer to different computers, it is so confusing that collectors have taken to referring to them by the year of their release.  The Kaypro II 82 is a different computer from the Kaypro 2 84 released two years later.  There is so much confusion caused by this so many articles online contain inaccuracies in describing the features and functions of the machines.

I've had a Kaypro 2 84 for several years, and acquired a Kaypro 1 from 1986 last year, but I've long wanted a Kaypro II 82 both for historical reasons, because it's the first of an iconic line of CP/M computers, and also for nostalgic reasons because my uncle who bought me my first computer bought one of these machines for my Grandpa and Grandma.  I knew from day one that Grandpa and Grandma's machine was a much more serious tool than the one that I had, and I thought it has an amazing design, it looked like a "real computer".

This Kaypro II 82 came from Free Geek Twin Cities via my friend Chris Gallaty.  Special thanks to Chris for getting this machine when he did and for passing it on to me.  The machine came with a note "Powers On - Keyboard Cable Needs Simple Repair".  One of the basic rules of troubleshooting is that you should not take other people's troubleshooting work at face value, you always want to do that work yourself, but I was hopeful that the label was correct.

The plug on the keyboard port had been smashed in and that repair did need to be done so I started out with the obvious repair first.  Chris has also given me a 4 pin modular jack from a phone handset.  Once I got inside the Kaypro the jack inside had taken a pretty hard hit and was beyond repair, so I needed the new part.  I soldered the replacement in and hot glued it on the inside to improve the support.  It feels quite solid.

I was able to drag out another working Kaypro machine and test the keyboard.  It was working as expected!

Next, I powered up the Kaypro II machine.  The CRT came up, but the normal prompt that appears on power up was not appearing, normally the machine would have a prompt that says 

*Kaypro II*

Please Insert a Disk

This message appears before booting and so a working floppy drive is not needed to get this message, just a working power supply, main board, and CRT.  I checked the power supply voltages and they were OK.  On the CRT I did not see any raster pattern when the brightness was turned up, or after adjusting the knobs.  I did some basic troubleshooting on the mainboard, and ended up moving the main board over into a different Kaypro.  I could see that it was outputting video, so that isolated the issue to the CRT analog circuit.  This was discouraging because I'm not the best at CRT repair, but I started doing some reading and found this article on Vintage Computer Forums.  I normally don't like doing "Shotgun" repairs, but I replaced as many of the caps as I could from my stock of Capacitors and that helped, now the image looked like this...

There was raster and the CRT was displaying text!  Also, I cleaned the disk drives with a floppy cleaning disk, and I made SS/DD Boot Disks for the Kaypro II.  The machine booted from the floppy!

The non-centered but visible image was evidence that I needed to complete the recap so I captured the rest of the capacitor sizes and put in an order on DigiKey.  When the caps arrived and I had time to get back to repairs on this machine I identified a large capacitor that was totally dead, so once the recap was complete, the image looked great and I completed the CRT adjustments.  I now have a fully functional Kaypro II machine...

I feel quite fortunate to have one of these systems, it's been on my wish list for quite some time.  My next project for the Kaypro II 82 will be make some more floppy disks.  I'm also thinking about swapping one of the drives for a Go-Tek as it would be really cool to be able to boot and run from Flash Storage.

Bargain Retro Computer Fixer-Uppers

It is quite common for me and my fellow retro computer collectors to complain about the high prices that Retro computer hardware gets on eBay, but there are still good deals to be had in local markets from people who are doing cleanups.  Personally I use Craigslist and Facebook Marketplace.  I find many of these deals as referrals from my network of friends who know I'm looking for these machines.  It's good to have realistic expectations going in, as most of these lower price computers will require repairs of some kind to bring them back to use.  

Recently I've been able to acquire the following small lots:

$70 for an Apple IIe and a tote full of retro PC software and hardware (Apple IIe was advertised as untested, and it had broken keys)

$50 for an Apple Macintosh Plus (Tested at the store before purchase, boots to ? icon)

$80 for an original Mac and a Macintosh Plus (advertised as not working, and without a keyboard, mouse, or other hardware)

None of these computers were advertised as working.  When I see a local ad like this, I look at the other items that this seller has listed.  If they have alot of Retro computer stuff for sale that is working then I'm less likely to believe that items are "untested", tested and not working is more likely.  But sometimes the seller will indicate that they don't have a monitor to test and I find this explanation more believable.  

The Apple IIe was listed this way, stating that the seller didn't have a monitor to test with and so it was sold untested.  Apple IIes are know to be quite reliable (unlike Commodore 64s of the era), and so when I got it home and connected to an Apple II compatible monitor, it fired right up.  I did have to replace a RIFA cap. in the power supply, and I had to remove the keyboard and replace two key switches and key caps.  This was something I knew would be needed going into the purchase from the sellers pictures and description.  I have fixed Apple keyboards before with parts I purchased from an eBay seller that specializes in Apple keyboard parts.  After the keyboard repair the machine was complete and fully functional.

The first Macintosh Plus was purchased because I have several of the early compact Macs and I wanted to have another computer of this type to use as a Parts machine.  This Mac Plus was working at the store, but I ended up spending time reflowing many of the solder joints on the Analog board to get it starting more reliable.  I also took the floppy disk drive out and lubricated and tested that.  This machine is fully working and I stored it with my other compact macs.

The original Mac and Mac Plus lot was not a purchase I had intended to make, but a friend tipped me off and since original Macs don't come up very often at a good price I gave the listing a good look.  The case was clearly in rough condition but I could see from looking at the ports on the back that the logic board was still inside.  So I made an appointment to buy the systems,  They looked as advertised so I paid for them and brought them home.  

At home, I confirmed that both of the systems were not working (the same symptoms the seller had indicated) and I got to work on the original Mac.  I was hoping that there would be enough parts to make at least one working machine from the two.  It turns out that the original mac wasn't booting because it has a memory expansion board that was not properly seated.  I removed the logic board, re-seated the card, and the machine came to life!

The second Mac Plus was more difficult to troubleshoot.  I have narrowed the problem down to the Aanlog board, but there are no obvious burn marks or leaking caps.  I have put this repair on hold for now and will store the Mac Plus with my other parts machines.  Even without getting this final Mac Plus working, this purchase was still a bargain, but I am sure that I'll come back to the Mac Plus at some point.

So, if you enjoy repairing retro computers there are still many bargains to be had on these machines, it just requires patience and a willingness to accept machines that may have some damage.  For me, I very much enjoy the hands on experience with these machines and so I'd rather have a good solid functional machine with some blemishes than a cosmetically perfect machine that doesn't boot up and run.

Have you fixed any vintage tech. recently?  Let me know in the comments below, or feel free to send me an email and let me know what you are working on.

My First PC - Slimline Gateway 2000 486

My first PC was a Gateway 2000 Slimline 486 which I think I got in 1994.  I've been wanting to re-acquire one of these machines for quite a few years since I got back into Retro Computing, but they've become a bit rare and I've been unwilling to spend eBay prices for one.  At the end of last year I got lucky and one came up for sale at Free Geek Twin Cities as a "Project Machine".   Free Geek is transparent about the problems with these machines and they sell them at really low prices.  The notes on the machine said "Floppy Controller Might be Bad", but the price was low enough that I could afford to fail.

When I got the machine home, I did power up the machine and confirmed the symptom, but I also noticed that the entire machine was filthy.  It wasn't just normal dust either, it was a thick sticky layer so I took the machine all the way apart and cleaned the circuit board with alcohol, opened the power supply and blew it out, and the case with water.

When I got the machine back together I was able to find notes about the motherboard on TheRetroWeb.  I was even able to contribute a BIOS dump and an image to the site!  Neither the floppy drive nor the CD-ROM drive worked on this machine.  I took them apart and cleaned the heads, but I wasn't able to bring these drives back to function.  I had the exact correct floppy drive and CD-ROM replacement from another Gateway 2000 machine that I'd tried and failed to repair earlier.

The other upgrades I installed include 16MB RAM and a Compact Flash adapter that is attached to a slot cover at the back of the machine.  This is attached to the IDE on the Motherboard and configured in the BIOS as a 485 MB HDD, but of course it is faster than a spinning drive.  But the main advantage of the CF solution is that it makes it easy to move files back and forth to the PC from a modern computer.  I also had a Sound Blaster 16 Value card from another lot of retro computer parts and I installed that into this machine as well as a 3COM Ethernet NIC card.

This machine is a 486DX2-66, and my machine was only 25MHz with 4MB RAM, so this feels really fast compared to what I had back in the day.  This machine currently has Windows 95 on it, but I may go back and setup another CF card with DOS 6.22 and Windows 3.1 which would have been what I ran on this computer back in the day.

I'm quite happy with how this build turned out and enjoying the nostalgia of having a Gateway 2000 machine configured with the options I really wanted back in the day.