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Thread: AT&T PC 6300 Revisited

  1. #31
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    Quote Originally Posted by Trixter View Post
    Try running "fdisk /mbr", and if that succeeds, run it again to see if it works. If that fails, boot a DOS 5+ disk (like MS-DOS 6.22) and try the same thing..
    I downloaded a set of DOS 4.01c 360k disks. I was going to try installing that if I couldn't get going under 3.3. I read that DOS 4.0 and greater could handle 2 Gb at the same time I found out DOS 3.3 could only handle 32 Mb. But I'll try FDISK / MBR first.

    Quote Originally Posted by Trixter View Post
    You're not doing anything wrong, just running into some bad luck. For a system of this vintage, with its various compatibility issues, I would try to stay as simple as possible: Try to use a 20 or 40MB MFM drive with the internal controller if possible. If not, try a small SCSI drive (under 100MB). Try running AT&T-branded MS-DOS 3.3 and keep each partition to 32MB or less just for testing..
    To quote Albert King: "If it wasn't for bad luck I wouldn't have no luck at all." I wanted to use SCSI partly because the controller and drive are more compact. I had a DEC / Conner 100 Mb SCSI drive that used to work but yesterday threw an error. All the other SCSI drives are larger, and many do not have the requisite 50-pin interface. All of the 8-bit MFM and RLL equipment I have seen take up quite a bit more room, and as I still want to run two drives; that means the drive and controller have to occupy board space and possibly cover slots.

    Quote Originally Posted by Trixter View Post
    Worse comes to worse, you can order one of the many XTIDE variant cards and use that with a compact-flash adapter (or a real IDE hard drive). The adapters must run in slow/8-bit mode with the 6300, but they do work.
    Got two, from glitch. That was Plan C.

    Quote Originally Posted by Trixter View Post
    It is unlikely that the display ICs are failing; it is much more likely that a capacitor is failing. Fortunately, that kind of thing can be easily serviced.
    I was hoping for an obvious sign like a leak or tilt but have yet to investigate.

    Quote Originally Posted by Trixter View Post
    If you want to remove the monitor itself from your troubleshooting, you can build a simple VGA adapter for the 6300: ftp://ftp.oldskool.org/pub/drivers/A...put_to_VGA.pdf
    That can help you continue your troubleshooting while eliminating the monitor as a potential issue.
    I was going to investigate whether the 6312 color monitor had the same connector as the 6300 but I'll look at the VGA adapter instead.

    My thanks to all for their suggestions.

    -CH-

  2. #32
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    Quote Originally Posted by clh333 View Post
    I downloaded a set of DOS 4.01c 360k disks.
    FYI, avoid DOS 4 like the plague. Any other version of DOS that came later provides only benefits without any downsides. I recall that 4.01c does fix all of the known bugs, but if you can run something clearly better that takes up less RAM (like MS-DOS 6.22 or IBM PC DOS 7.x), why not?

    Got two, from glitch. That was Plan C.
    I would get one of those set up (again, make sure 16-bit transfers are configured off in the BIOS that you flash to them, as the 6300 reverses the byte order of 16-bit reads due to an incompatibility) in a known working system, then transfer the card over to the 6300 and see what you get. Once you know your 6300 is 100% working with the XTIDE card, you can then go back to troubleshooting just the SCSI.
    Offering a bounty for:
    - Documentation and original distribution disks for: Panasonic Sr. Partner, Corona PPC-400, Zenith Z-160 series
    - Music Construction Set, IBM Music Feature edition (has red sticker on front stating IBM Music Feature)
    - Any very old/ugly IBM joystick (such as the Franklin JS-123)

  3. #33
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    I reinstalled the ST controller and the Quantum disk. Once again I began getting "illegal interrupt" errors (see pic attached) but DOS 3.3 boot concluded successfully. I ran FDISK /MBR, which encountered an error and terminated.

    I rebooted, this time with the DOS 4.01c installation disk, and got part way through the installation before it, too, encountered an error and terminated. I rebooted DOS 3.3 and re-ran the Ontrack Disk Manager program, with same results as before.

    I tried to install the XTIDE card I got from glitch but due to a clearance issue was unable to install the card. I removed the ST controller and Quantum drive.

    It's hard to know what the cause of the problem is, especially with the concomitant video issue, but my guess is that the ST controller is either mis-configured or defective. My documentation for the controller is pretty sketchy so I think I'll have to find better documentation to know for sure. In the meantime the Quantum can be used elsewhere.

    On further consideration trying to use the 6312's color monitor attached to the 6300 does not seem like a good idea, as the 6300 is sending power to the monochrome monitor. I'll try building the adapter shown in the link.

    Thanks again,

    -CH-

    IMG_2374.jpg

  4. #34
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    If the M280 video connector is the same as on M24, then you can use the monitor. There is also a color monitor for M24 and this one also has it's own power supply and does not use the M24 graphics card as power supply.

  5. #35
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    Quote Originally Posted by 1ST1 View Post
    If the M280 video connector is the same as on M24, then you can use the monitor. There is also a color monitor for M24 and this one also has it's own power supply and does not use the M24 graphics card as power supply.
    Thank you for the suggestion. However, it's looking more and more like the problem is closer to the motherboard.

    I was able to resolve the XTIDE clearance problem and after determining its ability to boot on an IBM XT I moved it over to a slot on the AT&T. The machine recognizes the XTIDE and will boot from either the A: drive or the XTIDE (when it boots correctly, that is), although there isn't much more than DOS 6.22 and a few XTIDE utilities on the flash card.

    The garbled display on startup is getting worse, in this sense: The screen bar pattern seen before persists for the first few resets, and the characters are still in the wrong place, but now the character set is becoming garbled as well (CHR$ > 127). The cursor flits all over the screen and sometimes the A:> drive light will come on but not boot. After a few minutes - and several resets plus maybe a power cycle - the machine will settle in and complete a boot.

    This is looking like a timing issue and it also seems that it is affecting more than just the display. I'm wondering if it is somehow related to the system clock. More investigation is required.

    Thanks again,

    -CH-

  6. #36
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    Either your RAM or capacitors are going bad. It's not a timing problem (unless related to the caps).
    Offering a bounty for:
    - Documentation and original distribution disks for: Panasonic Sr. Partner, Corona PPC-400, Zenith Z-160 series
    - Music Construction Set, IBM Music Feature edition (has red sticker on front stating IBM Music Feature)
    - Any very old/ugly IBM joystick (such as the Franklin JS-123)

  7. #37
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    Well, I'd probably start by cleaning and res-eat all of the boards, including the video cards, making sure that the power supply connections are nice and tight.

  8. #38
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    Good advice, thanks. I'll try that first.

    -CH-

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