Wednesday, September 7, 2016

#141) Looking for Librascope L107MA Disc Memory information

The other day I received the following request (edited) from Josh Dersch, who restores old computers as a hobby and as a full time job at the Living Computer Museum in Seattle (click here). This museum was co-founded by Paul Allen, owner of the Seattle Seahawks and co-founder of Microsoft.
PS: If you are reading this post in an e-mail, you can leave a comment beneath this post (#141) on the blog's website (click here).

Hello --
I recently picked up an L107MA Disc Memory unit, and I was curious if you had any technical information about it, or know anyone who might - the Librascope Memories site has brochures covering the basics, but I'd like to be able to spin it up and interface it to something, so I need something with a bit more substance to it :).

I picked up the L107MA off of eBay last week from a seller in Santa Cruz, CA. It was reasonably priced for something this cool, under $200. (The seller now has a second unit listed for $225 -- item 331955558119).

I restore old computers as a hobby, and as a full-time job at the Living Computer Museum in Seattle. I have a decent collection of DEC and Data General hardware from the '60s and '70s. I'm hoping to interface the L107MA to one of my vintage machines (but I'll probably start with a modern micro-controller to get a feel for how it works).

I have attached a photo of the unit I have. It's missing the cover, but is otherwise in excellent condition, and was shipped to me in what appears to be the original box/packing materials.

If no specs or manuals are available, what would be excellent to have would be what the interface to the drive looked like (recalling the pinouts from memory seems unlikely, but knowing if the interface is serial or parallel, how blocks were selected, etc. would be useful).

Thanks very much for the help, and the wonderful website! Feel free to post my question on the blog; hopefully, someone out there has some information.
- Josh


  1. Comment from Tony Cappellini - Note, I sent Tony a much better copy.
    Hi Carl,
    How can I get a larger picture of this L107MA advertisement? I cannot read the text from the LM page, as the image is too small.

    I'm trying to help Josh find information about the L107MA Disk Memory.

    I remember going into the assembly room for these in B17. Warren Douglas took me there once, but I didn't work on them.

  2. Comment from Don Barton, Program Manager -
    Hi Carl,
    I wish I knew more about the interface between the disc electronics and a controller. As I recall the users (customers) usually designed their own controllers to suit their application.

    My first concern, when I read the note, was that there was no cover on the memory unit. As you recall, the L107MA (and all the disc series) had to be hermetically sealed, and a desiccant was used to reduce/remove any moisture from the disc cavity. Any attempt to spin up the coverless disc could be catastrophic at this time. The head per track interface needed to be dry. Any hang up of a head on the disc could be fatal to the disc. In my opinion, any disc memory in storage for a long time (a decade or more), even with a cover installed, would require it to be disassembled and cleaned in a dust free environment before any attempt to power it up.

    Sorry I couldn't be of help for Josh.