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Thread: Original Tandy 1000 hard drive bringup

  1. #1
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    Default Original Tandy 1000 hard drive bringup

    I have an original Tandy 1000 with a memory expansion board (reports 640KB on boot) as well as a "harcard". Need to take a closer look at the board for more markings, but the controller has a "WDC '85" chip on it and the drive is labelled as a MiniScribe (19 CYL, 3 HD, 3354 BYTE).

    I've read through the "Hard Disks" section of http://www.oldskool.org/guides/tvdog/1kfaq.html#II.D twice now and still a bit unsure of what to expect. Most of the information seems to be regarding later models in the 1000 series.

    When I first powered on the machine, I had no idea it was present, but the card was plugged in to the bus and power was connected to the drive. It did not boot off of the drive but rather (after a long delay!) would expect a system floppy disk to be inserted before proceeding. Once I opened the machine I unplugged the power connector to the HDD as a temporary measure so that it wouldn't cycle so much during other work/testing. No change to the boot behavior.

    Now I would like to plug it back in and try get any current data backed up, and then use it. What should I expect? Should it actually be booting from the HDD if it were working, rather than expecting a DOS floppy? Or at least, should it show up as a C: drive once DOS 2.11 is started via the A: drive? Or was it only useable with particular software e.g. Personal DeskMate?

    Also, are there any precautions to take before reapplying power to an aging drive like this?

  2. #2
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    Couldn't find any general label on the ISA card, but its layout and jumpers seem to match the WD1002A-WX1 listed at https://stason.org/TULARC/pc/hard-di...2-MFM-dri.html, which also has some datasheets linked from https://slomkowski.eu/retrocomputing...ibe-hard-disk/

    The drive is a MiniScribe model 8438 (the "specs" I gave in the previous post was actually the list of known "as shipped defect criteria"). There's one little lever thing on it that I messed with before reading the sticker further over with an arrow in its direction "DO NOT ROTATE INTERRUPTER". So I'm off to a good start then, eh?

    If I boot the machine without the card, it starts up significantly quicker. With the card in and power connected to the drive, I did hear/feel the drive do a little startup dance at least once but no messages are visible during the "slow" part of the boot up. After booting to the DOS floppy disk that came with the machine, typing "C:" at the prompt complains "Invalid drive specification".

    I am able to use the DEBUG command on my DOS disk followed by `g=C800:5` at its prompt to jump into a "Super Bios Formatter Rev. 2.4 (C) Copyright Western Digital Corp. 1987" which claims "Current Drive is C:" and "Current Interleave is 4". I did not proceed with a low-level format because I want to get any data off this drive first.

    But how do I get the data off if DOS doesn't know about any "C:" drive? Even if the drive is bad, shouldn't it at least give me some sort of read error instead of just saying it's an invalid letter?

  3. #3

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    Those MiniScribe 3.5" drives often suffer from stiction (the heads sticking to the platters), and to get them to spin up again you need to rotate the interrupter, despite what the warning sticker says. It also really helps to oil the stepper motor, as shown in this video:


  4. #4
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    Quote Originally Posted by natevw View Post
    I have an original Tandy 1000 with a memory expansion board (reports 640KB on boot) as well as a "harcard". Need to take a closer look at the board for more markings, but the controller has a "WDC '85" chip on it and the drive is labelled as a MiniScribe (19 CYL, 3 HD, 3354 BYTE).
    This type of hardcard was a common upgrade for the first Tandy 1000 (but I don't think you wrote those drive params correctly, there's no way it has only 19 cylinders).

    When I first powered on the machine, I had no idea it was present, but the card was plugged in to the bus and power was connected to the drive. It did not boot off of the drive but rather (after a long delay!) would expect a system floppy disk to be inserted before proceeding.
    This implies the drive is dead. Try the "stiction" fix and see if you can get it to spin up, at least.

    Most hardcards are dead these days, so this is not an unexpected result. You asked "shouldn't I see an error?" Usually yes, during the POST, the controller should print out "1701" or similar as a hard drive error. Do you see any errors flash by quickly on bootup before it asks for a floppy disk?
    Offering a bounty for:
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  5. #5

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    I've got a Quantum HC EZ170 170MB that works fine. It's 16-bit so it's no good for this particular application. It's available if there's interest.
    PM me if you're looking for 3" or 5" floppy disks. EMail For everything else, Take Another Step

  6. #6

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    The totally sealed Quantum HardCards were already failing back in the '90s. But Tandy's "hard cards" were really just a standard 3.5-inch hard drive bolted to a matching 8-bit ISA controller card.

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    Thanks for the tips. My stepper motor isn't quite as accessible since there's a sort of lever/cam attached to it which homes itself in something that looks like it's a sensor. But I did drip a few drops of Super Lube (PTFE oil) onto the shaft above.

    IMG_20200129_185711159-resize.jpg

    It does not appear to be stuck, at least not any longer. The spindle motor also seems to be running at a pretty good clip, although I can't really access it without splitting the drive mechanics from its own PCB which for now didn't seem worth it unless there's good reason to.

    When the drive is powered up (WD controller card or no) it does a little cycle of wiggling the stepper, then turning it almost full circle with kind of a grinding noise at that end, and then back to the "home" spot. It repeats that three times, then never moves again even when the drive is connected to the card and computer on bootup.

    Does this point to an issue with the WD controller, that it's not even trying to run the drive? As I said, its format utility at C800:5 is working fine and there doesn't seem to be much on the board besides a handful of Western Digital ICs.

    Or can the drive itself detect a problem during its warmup routine and let the controller know to not bother it?

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    Forgot to mention, I do not see any drive related errors on bootup. The display goes near-instantly to a single big/bold line about "640K memory" as soon as the power switch is thrown, and it's during that time the drive does its own power-on dance.

    When the card is plugged in, the Tandy sits on that memory screen for an extra long time, and then as far as my eyes can see flips directly from that "640K" line to a paragraph in a smaller font about its own 01.01.00 BIOS followed rapidly by the insert system disk message.

    Is there a way to probe the controller via DEBUG or other tool, to get status information that might reveal more about where the problem might be between the MiniScribe drive or the WD controller?

  9. #9
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    Noticed a plastic block for an LED on the drive's PCB while I was messing with it earlier, thought it was just for an activity light. But during some continued research this evening found mention of these being used for error messaging as well!

    Indeed, after the first couple cycles [or maybe sooner] I get a pattern: dah dah didididi dah

    I found a guide for this particular drive at https://stason.org/TULARC/pc/hard-dr...RLL-ST506.html which I'll need to scour a bit further for any other tips, but it's not particularly helpful for the "flash code". The sibling M3650-42MB-5-25-HH-MFM-ST506.html page explains it a bit better.

    If I'm translating correctly, the signal is 1101 (Code D) which isn't given in the M8438 guide but both the M3650 and the M8438F-33MB-3-5-HH-RLL-ST412.html guide list the same as https://archive.org/details/h42_Phil.../n137/mode/2up does for the MS3212 as well:

    "Seek error during burn-in or recal"

    Now…what does that mean? Jumper 13 is open, so I'm not sure why burn-in/recal would be at play at this point?
    Last edited by natevw; January 29th, 2020 at 08:03 PM.

  10. #10
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    Success!

    I'm not sure what fixed it — squeezing/shaking/blowing another 5–10 drops or so of PTFE oil down the stepper shaft, manually rotating the interrupter a bit more, or blowing off the interrupter's sensor. Re. the latter I noticed when I left the interrupter NOT near its home position, during the bootup cycles it would do its spin thing and return to WHERE I LEFT IT (!) rather than the home position. The computer and drive are hardly dusty but it made me wonder if the optical sensor wasn't reading.

    Anyway, after the oiling/rotating/blowing the drive got to a point where it seemed to pass its own self-test on the LED. At this point the Tandy 1000 changed a bit, on startup with no floppies it now said "Disk Boot failure". At this point, booting from a DOS 2.11 floppy still refused to consider C: a valid drive.

    Power cycled once or twice, then pressed RESET once or twice while still powered on and (as they say in the industry): BOOM!

    It booted up to a C:> prompt!!

    At this point I began frantically looking for blank floppies to back things up just in case this was a one-time offer. It locked up once while doing this (might have bumped the HOLD or PRINT key or something?) but rebooted fine. Long story short, I rotated a handful of floppies between `BACKUP c: a: /s` running on the 1000 and a SuperCard Pro drive from a laptop. Thirty eight disk swaps per machine later and I think I have all the current filesystem entries backed up

    Now that I have that, I've started playing around a bit. The drive boots into DOS 03.30.20. So far I've found DeskMate of course, PFS First Choice, The Print Shop, Flight Simulator v3, Arcadia Double Dragon, and seems like there's plenty more games/utilities for another evening.

    OPTune 1.2 (disk utiltity I found on the drive) verified the whole disk, a couple angry noises but everything "verified after retry". Proooooobably not going to store any incredibly important work on this drive, but excited to have gotten this far. Fun rig!

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