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!