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Thread: 8" and 5.25" Floppy Drive Sales, And Repair

  1. #11
    Join Date
    May 2018
    Location
    North Dakota
    Posts
    10

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    Hello, I inherited a trs 80 model 2 and I cannot get past a boot dc error. I know the disks are fine so I would like to send the shugart 801 to you for testing and repair. Visually it’s looks to be in good condition but it has been sitting for decades Are you interested

  2. #12

    Default Repair of 8” Siemens Drive

    Hello,

    If you are still servicing drives, could I send you the unit with issues described below for repair? What is the procedure/cost.... Thanks, Tom

    Quote Originally Posted by MicrocomputerSolutions View Post
    If the drives will read the boot disk after you manually set the head to Track Zero, I would say your problem is that the Track Zero Sensor needs to be adjusted. If the Track Zero Sensor was not working at all, manually repositioning the head assembly would not help.

    The way that Track Zero works on most 8" drives, is a mechanical flag mounted to the head assembly interrupts a light sensor mounted on the chassis towards the rear of the floppy disk, two-four motor steps before the heads reach Track Zero on the floppy disk. The drive's logic keeps track of when the Track Zero sensor indicates the Track Zero Sensor flags, and knows that the next time the stepper motor located to Zero Winding, the heads are located at Track Zero.

    When we use an alignment tester, or oscilloscope and a alignment disk to find Track Zero. We move the drive's head stepper motor to the Zero Winding, then mechanically adjust the head assembly so we can read the Track Zero Signal on the alignment disk.

    It sounds to me like the Track Zero Sensors on your drives are working, but the Track Zero Flags on the head assemblies are mis-adjusted, so the flags are tripping the Track Zero sensor too early or too late.

    IF the drives were sent to me for service, I would start by set the head alignment, then set the Index alignment, and then reset the Track Zero Sensor alignment., before testing the drive on a computer for proper operation. You must set the head alignment first, so you can accurately set the Track Zero Sensor flag to the write track so it will flag before the head reaches Track Zero.

  3. #13

    Default

    Quote Originally Posted by lutiana View Post
    Might be a good idea to put a location in your profile. This helps people get a sense of the shipping cost to get the drives to and from you. Does not have to be your exact address, just the state would suffice.
    Michael Louie (Microcomputer Solutions) was based in Rialto, CA

    Quote Originally Posted by GeoffB17
    I have the disk drive unit (only) from an old IBM DisplayWriter system. This contains two 8" drives. I believe one is a lower density drive, and the other is the higher type.
    This does NOT use the standard connectors mind you, it's a plug/socket like the standard serial connector, but longer.
    What might be my chances of ever getting such drives working, say with a CP/M machine? Might a PC be a better bet?
    Geoff -
    Very familiar with the IBM DisplayWriter and the IBM 6360 Dual 8” Floppy Drive Cabinet (often called “The Toaster”).
    About ten years ago, I looked at the DIY work required to interface the 6360 to S-100 systems or 1983 IBM-PC/XT.
    I elected not to pursue, after reading MichaelÂ’s earlier postings and potential scarcity ($$) of future repair parts.


    Some Quick Facts:
    * IBM Displaywriter System, released in June 1980, used an Intel 8086 processor.
    Supposedly, in early 1980s, a version of CP/M was ported ... but unlikely officially released.
    https://en.m.wikipedia.org/wiki/IBM_...ywriter_System
    * The 6360 System used three different types of 8” floppy drives, defined by “IBM Type”
    Type 1 (SSSD), Type 2 (DSDD), and Type 2D (DSDD)
    During this time period, IBM used 8” floppy drives on their System 34/36/38 computer system
    as well as older IBM SNA mainframe terminal controllers (3274)
    https://en.m.wikipedia.org/wiki/List...8-inch_formats
    ===
    Michael provided good advice about IBMÂ’s early drives, due to their proprietary parts.
    There are some small shops and former IBM Techs that work on these drives (IBM dropped support in late 1990s),
    for support of older IBM System 34/36 owners.

    One DISADVANTAGE is that the Type 1 and Type 2 floppy drives are BELT DRIVEN (Not Direct Drive),
    hence speed accuracy (slipping, worn belts) is less precise.

    While the IBM 6360 could be adapted for S-100 computer usage ... it REQUIRES KNOWLEDGE and GOOD DIY Skills.
    For example, DC Voltage sources (24 Volts) and Custom cable building from the 8” Drive (inside 6360) to your S-100 controller card. The original IBM Displaywriter had proprietary floppy controller in its base (below monitor) with proprietary cabling.

    gb

  4. #14

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    Geoff -

    The IBM 3740 was released in 1973 and featured the first usage 8” floppy drives/media (first standard). IBM 3740 format 8-inch SSSD disk 241Kb (77 tracks, one head, 26 each 128 byte sectors per track with a skew of six).
    This was the disk format used for exchange between all the CPM-80 8-inch systems and software providers.
    https://en.m.wikipedia.org/wiki/IBM_3740

    This Wikipedia page should be helpful.
    Many of the IBM Displywriters used Single Sided drives (Type 1, 33FD),
    only the later production models used Double-sided drives.

    https://en.m.wikipedia.org/wiki/List...y_disk_formats

    Bill Beech, NJ7P has a nice write-up on Floppy Drive Formets, Standards, and Geometry
    http://www.nj7p.org/Computers/Disk%2.../floppies.html
    ===
    Here are two (2) “Widgets” that may help with your IBM 8” Floppy Drive project.

    One handles 50-pin Data/Control, the other addresses 24V requirement of 8” floppy drives.

    FDADAP Board
    http://www.dbit.com/fdadap.html
    The D Bit FDADAP board is a small adapter which adapts 8" floppy disk drives (Shugart SA800 style bus) to work with the PC 3.5"/5.25" floppy disk cable pinout. It has 34- and 50-pin connectors which can be connected to the PC floppy controller and the 8" disk drive using simple straight-through ribbon cables (not included), and a 3.5" style power connector for the on-board microcontroller.

    FDDC Power Converter
    http://www.dbit.com/fddc.html
    The D Bit FDDC is a DC-DC converter which boosts/negates the voltages from a PC power supply to those needed by most 8" floppy drives. It can attach to an IDE power connector on a PC's power supply that has sufficient capacity to power both the PC and an 8" drive, or it can work stand-alone from its own dedicated ATX power supply (it has circuitry to drive the ATX "power-on" signal using a momentary pushbutton as input). The outputs are supplied via a 6-pin AMP Mate-N-Lok connector using the standard Shugart pinout.


    D Bit
    139 Stafford Road
    Monson, MA 01057
    e-mail Inquires: info@dbit.com
    Voice: +1 (413) 267-4600

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