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Thread: Mitsubishi M2894-63 8" Floppy Does Not Respond To Controller

  1. #1

    Default Mitsubishi M2894-63 8" Floppy Does Not Respond To Controller

    Hello,

    Over the past couple of days I have been trying to get one of my Pentium PC's hooked up to a 8" disk drive system that I cobbled together using some parts I had gotten earlier this winter. It consists of two Mitsubishi M2894-63 disk drives inside a Sperry-UNIVAC case. As far as I know, all power is good as the disk drives start spinning and flash on for a brief second. I have been trying to use one of the DBIT 34-50 pin floppy adapters to hook one of the drives up and image some System/36 disks. I am using the same setup I used a few years ago to create TRS-80 Model II disks, so I know the floppy controller + adapter I am using have worked successfully in the past. So my current setup consists of one of these disk drives, set to drive #0 with the terminator block in, and the other drive unplugged. My computer is set up so drive A: is a 5.25 1.2M disk.When I turn it all on, everything seems fine, but the disk drives simply do not respond to any commands I give it. For example, a FORMAT A: command will have the DBIT light up track "00" for a half a second, then will turn off and the computer will state that the drive is not ready. I have tried switching drives and cables to no avail. I'm not really sure where to go next.

    Thank You.

  2. #2
    Join Date
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    Sometimes you can figure basic functionality by disconnecting the signal cable and grounding the various pins. For example, when a disk is inserted and the corresponding drive select is grounded, does the READY/ line drop to nearly 0V?

    Like a lot of 8" drives, the Mitsubishi drive is nominally Shugart SA800 interface, but there are a lot of option jumpers. You should probably start by checking those out first

  3. #3

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    My M2896 works fine (also with dbit interface). Read through my internet pages. Maybe it will help you. There you can also see my jumper settings.

    https://retrocmp.de/index.htm#8inch

  4. #4

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    Those who can read have a clear advantage in life. M2894 not M2896. Oops! My mistake. But nevertheless, the problems should be similar.

  5. #5
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    Just a couple of thoughts - is there a known good soft sectored disk in the drive? Perhaps try running ImageDisk in alignment mode and see if it lets you step the heads or do anything else.

  6. #6

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    Sorry for not responding for long, I have been having a very busy week, thank you to everyone who responded and messaged me.

    So tonight I took another crack at the Mitsubishi drives. I took down my PC with the DBIT adapter and instead got out my H11A with Sigma 400255 card installed. The manual claimed compatibility with the Mitsubishi M2896-63 drives, which from what I have read are very similar to the M2894s. I set the M2894 to the approximate prescribed settings for the M2896 that the manual laid out. After hooking it all up and powering it all up, I still got no response. After that, I got out and tested some of the edge connectors. I grounded DS1 and tested the READY line, but the voltage hovered around 0.15V regardless of if a disk was in it or not. I just have it jimmy-rigged right now so I may have something incorrect that is causing this, so I will look at this in the morning. I am assuming that this is either some sort of jumper misconfiguration or part failure.

    Thank You, Gavin

  7. #7
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    READY/ should have a pullup on it, so when not active it should hover near +5. You do have the terminator installed, don't you?

  8. #8

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    Alright, small update

    I checked the voltages on the disk drive I was using, and it appears there is a faulty component. 5V was getting pulled down to ~3V and 24V was getting pulled down to almost nothing. After unplugging the faulty drive, along with changing some of the disk drive settings on my remaining 8" drive, I was able to get it to function. I tested it with my H11A / Sigma 400255 and it was able to talk to the drive and format a disk via ODT commands. I also dragged out my DOS computer with DBIT adapter, and was able to use IMD118 to image one of System/36 disks. I will be imaging the rest of my large S/36 disk collection tonight or tomorrow, so if anyone has any interest archiving them, PM me. I will also be looking to see if I can identify what component is faulty on my other disk drive tomorrow, so hopefully I can get both drives in my enclosure functioning.

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