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

ThisPostContainsComputers

ThisPostContainsComputers

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Oct 31, 2015
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Minnesota
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.
 
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
 
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.
 
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
 
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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