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TRS-80 12/16/6000 Restoration story

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    TRS-80 12/16/6000 Restoration story

    Having owned a number of these machines as a teenager, finishing up with a brand new Tandy 6000 that I purchased at a Radio Shack tent sale around 1990, I felt that it was important to share my experiences with others who are interested in these systems. The 6000 was the most memorable, as this served as my first UNIX like system administration experience. I ran this machine for a few years while in college, with family and friends using terminals and a dial-in modem to access email and such, much like a dial-up BBS. I went through several hard drives before the power supply went out, and I finally moved on to Linux on a 386 PC, at this time the kernel was around .9x version and I remember multiple times having to compile the kernel to get things working. Unfortunately, many of the pieces of this trs-80 collection were lost over the years, but I still held on to all of the manuals, diskettes, some hard drive enclosures, and the 6000 itself, minus the top cover and power supply.

    In mid-2015, I started thinking about this system a lot, and decided that it was time to pull it out of storage and see what could be done to restore it. The power supply was the first order of business, I watched a few on eBay for a while, then I received a tip that there was a modern power supply that would fit and provided all of the needed voltages (the 24V supply was the unique part). Not wanting to deal with capacitor flame-out, I opted for the new power supply. Jameco to the rescue, although they didn’t remember my account from back in the ‘80’s, I was happy to see they were still around. Once the new power supply arrived, I started disassembling and cleaning things, and started with just the system board, video board directly in the slot on the system board, CRT, and floppy drive. Fully expecting the CRT to explode in my face, I flipped it on and was surprised that nothing obviously bad happened. The CRT did power up and raster lines were visible. After several rounds of plugging/unplugging, reseating chips, swapping RAM chips, etc, I began to get something on the screen that resembled English. Reseating the video board multiple times eventually got to a place where I had a readable error message, “BOOT ERROR” on a green background. Reading through the service manuals, and doing a number of searches online, this did not appear to be a documented error state. Every boot error I found had a two letter code after it that indicated what was failing. For some reason, I had a second system board but it ended up having the same issue. At this point I became convinced that there was something wrong with the floppy drive, and the system was just giving up rather than at least prompting with the typical “INSERT DISKETTE” message.

    A few months passed with little change, until I came across a lot of equipment for sale that included a working model 12, as well as a dead 16b, manuals, and diskettes. It was more than I needed, but having spares was good, and maybe I could get two working systems from the three. As it turned out, the 16b was in really poor condition, and the case was terribly yellowed. As my goal was to get a museum-quality restoration out of this, I decided to consolidate everything down into the model 12, as it was in excellent shape with matching keyboard. Once I had the working model 12, it didn’t take long to verify the condition of all of the spare parts, and it turns out that my original assessment was not correct. The 6000 system board was at fault, rather than the floppy drive. That drive ran perfectly on the model 12 system board.

    Since the model 12 did not include the expansion card cage, I had two options, the one from the 6000 or the one from the 16b. I decided on the one from the 6000, as it had the modifications noted in some service bulletins that I found online. Namely the plastic card guides and some capacitors added to the bus. At this point, I had no trouble booting to TRSDOS 2.0, and occasionally 4.2 would also boot. Not sure if this was a floppy issue or RAM. It was time to start working on the hard drive.

    As I mentioned at the beginning, I had a total of three external hard drive enclosures. (Not including the 8” drive that came with the model 12). Although the 6000 had come with the type 4 controller, for some reason that board was missing from my 6000, and instead I had the type 2/3 configuration with the 50 pin cable. Luckily I had one of the enclosures that included the small WD-1001 controller inside. I proceeded to combine the best condition parts from the three enclosures and chose one power supply that was working well to complete the enclosure assembly. Now, if I just had a disk drive for it. Not having anything MFM at the time, I landed a Seagate ST-251-1 from eBay that was sold as guaranteed working. When the drive arrived, I promptly tested it on an XT class PC and the drive worked just fine. However, when installed in the Tandy, it would never format. I tried many times, both diskutil from Xenix and TRSDOS-II 4.2. Diskutil sometimes seemed to get farther along, TRSDOS always reported drive not ready no matter what I tried. Again, I started to speculate that perhaps one of the two boards for the disk controller was bad. It generally gave “BOOT ERROR HC or BOOT ERROR H0” at power on, which led me to believe that it was at least trying to access the disk. And the active lamp on the disk enclosure generally behaved as expected. In addition, I knew the RAM on the adapter board was good, since I was now able to reliably boot TRSDOS-II with the board installed, and it would not boot with the board removed. (TRSDOS-II requires 96K, the remaining 16K is on the hard drive adapter).

    So, time to wait some more. In talking with Peter Cetinski, he offered to send a diagnostic disk, something I had never seen for this system. Once that arrived, I was pleased to see that the disk controller passed, and it was able to format the hard drive just fine. However, I still got drive not ready when trying to format under xenix or TRSDOS. During the wait, I had picked up an excellent condition IBM 5160, which happened to include a working 20 MB MFM drive, MiniScribe 3425. While I was much more interested in the speed and reliability of the Seagate drive, I decided to try swapping them. Much to my surprise, it too passed the diagnostic test, and even through TRSDOS still gave the “drive not ready” on format, Xenix diskutil was able to format the disk with no troubles at all. So, I finally felt comfortable that the disk system hardware was working properly. Since I intended to run Xenix anyway, I knew I still needed some work on the 68000 boards.

    Since getting to the point that I could boot from floppy, I had tried several times to boot some of the various Xenix disks I had laying around. Some of them were completely shot, but I had several of the 1.3.5 disk sets, and I had my original 3.02.00 disks that came with my 6000. I had another set that was an earlier 3.0 version as well. One set consistently gave the “BugHlt No68k” message during boot. I had two sets of 68k boards/ram, one from the 6000 and one from the 16b. I had been using the one from the 6000, as it had a full 1 meg on a single RAM board, the other had 3 256k RAM boards but the CPU board was still the later version not the “dog ear” one. I tried the older board set, and got to a point where I received a” memory verify” error. After the usual reseating, cable swapping, etc I ended up with 2 of the memory boards with the 16b CPU board and had a working 68000 CPU!
    Other than the keyboard rebuild that was still needed (which I won’t cover here), I had fully working hardware in place. Time to install Xenix. Break out the disk drive head cleaner, it’s going to be a long night. Nearly every diskette I tried left gunk on the heads, I must have cleaned the drive ten times before I got an install to complete. I had at least three sets of 1.3.5 install disks, and one of them seemed to be ok. Unfortunately, I only had the one 3.2 install disk set, and the first disk was bad, consistently gave IO errors. So, I decided to push forward with the 1.3.5 install for now, maybe I can upgrade later. With a clean drive head and a good set of install disks, the install went relatively smooth. Pretty soon I had xenix up and running. Just for fun, I tried to install the 3.0 development system, but of course it failed, stating that it required 3.0 or later. Thankfully, I dug around and found the 1.3 development system disks that had been part of that model 12/16b lot. Amazingly I was able to get through disk 8 of 10 before errors started and floppy drive noises forced me to quit. It would be nice to have the full install, but I got what I was after, games and vi.

    During the fall, while waiting for some parts to come available, I had picked up a Wyse-60 terminal. This was another piece that had some nostalgic value as it was what I used in college for most of my UNIX work there. I knew that I wanted one for the collection, and found one in mint condition with the green screen, exactly what we had in the VCU computer labs. Once I got my Xenix system up and running, I proceeded to configure this terminal to work with the system. Enable tty01, edit the /etc/ttytype file to set the correct emulation (with a little help from the xenix operating guide on bitsavers), and locate a proper serial cable and null modem, and it might just work. Well, the third serial cable worked, the first did not work at all, the second one would work then randomly the characters would be garbled (pressing a letter would display a different letter). I fought with this for quite a while, going through multiple flow control settings and such on the terminal. Finally I tried a third cable and it works perfectly.

    So, six months after starting this project, I had a working xeinx system that does exactly what I wanted it to do. This was by far the most complex restoration I have done to date but in the end it was worth it to see this system live again. It was also more costly than I wanted it to be, but hopefully we can recover some of the cost selling off unneeded spare parts. I know that these machines are increasingly rare, and there are not many collectors interested in working on them. I am happy to have this in our collection, and grateful to share what I have learned with others who might be interested. I hope that you find this helpful, and feel free to contact me with questions or suggestions. I have sold some of the spare parts, but I still have some spares if there is something you are looking for, just let me know. Thank for reading!

    If you want to see some photos of the process, check out the restoration page on our web site:

    http://www.vacomputermuseum.org/coll...re/tandy-6000/

    #2
    Great story! It really depicts many of the trials and tribulations we enthusiasts go through to get these big Tandys working again. A labor of love for sure. Spare parts, patience and a lot of time are essential.
    Pete
    http://pski.net

    Comment


      #3
      Hi, VCM!

      I came across this thread as Pete Cetinski has been mentoring me through a rescue of an old Model II. This machine has a bad 5V line on the extant power supply and Pete recommended the RQ125D as a modern replacement. I have a good conceptual idea of how to replace my bad AQ supply with the RQ125D by cannibalizing the old wiring harness and using some butt connectors ... but I have two questions: 1) How hard is it to retrofit the 125D into the existing case? 2) Could you share any documentation you have about the wiring harness you constructed? I saw the photo on the web page, but I could not easily enlarge it.

      Thanks!
      -gk

      Comment


        #4
        if you want to make a short harness that plugs into the existing DC harness, the connector you need is a uni-mate 15 position 94V-2, digikey A1463-ND. you'll need to buy the pins for the connector shell which are available at digikey as well.

        A14300-ND
        A14298-ND
        A97892CT-ND

        IMG_3929.jpg IMG_3928.jpg

        you can select the pins depending upon the size of the cable.

        for the 3position AC connector:

        A112253-ND shell
        A1441-ND pins

        IMG_3930.jpg IMG_3931.jpg

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