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Thread: microPDP-11 Rebuild (Saved from going to the trash!)

  1. #1

    Default microPDP-11 Rebuild (Saved from going to the trash!)

    Howdy all,

    I managed to come into possession of a lot of PDP hardware, including most of a entire rackmount PDP-11/44, tons of spares, a microPDP-11, and various VAXstations with accessories.

    I am starting the restoration work with the microPDP-11, as it has the easiest learning curve to get to understand it, since it was available up until 1990!

    This thread will track the progress. The computer was in excellent condition, and I believe it was still used until some minor failure. I work as an electronic specialist at a local laser gas detector company, so I have access to many interesting resources to assist in my projects, so pretty much no advice will go unheeded... if I need to build an interface board, so be it; if I need to build a cable, so be it, if I need to solder a bunch of components and/or test others, so be it.

    Currently I have physically cleaned it up and have powered it on. I have a virtual terminal device that connects to the D0 output that takes a PS/2 keyboard and VGA output, but it currently cannot seem to talk to the terminal at 9600 baud, 8+1, no parity (it matches the rear console settings). As I left it running, it started to smell exciting, so I have powered it down and will begin rebuilding the power supply to spec. Currently the front lights are green for RUN. I will attach some photos to the next post.

    I hope my adventure will be interesting to some of you. I have never worked on "mainframe" systems before, but I have plenty of experience with 8086 systems and upwards. I have been watching a lot of interfacing videos and restoration of big mainframes, so I understand the theory of how they operate deI also work as an electronic specialist at a local laser gas detector company, so I have access to many interesting resources to assist in my projects. ^_^

  2. #2


    Computers: Amiga 1200, DEC VAXStation 4000/60, DEC MicroPDP-11/73
    Synthesizers: Roland JX-10/SH-09/MT-32/D-50, Yamaha DX7-II/V50/TX7/TG33/FB-01, Korg MS-20 Mini/ARP Odyssey/DW-8000/X5DR, Ensoniq SQ-80, E-mu Proteus/2, Moog Satellite, Oberheim SEM
    "'Legacy code' often differs from its suggested alternative by actually working and scaling." - Bjarne Stroustrup

  3. #3
    Join Date
    Oct 2008
    Kamloops, BC, Canada
    Blog Entries


    Welcome to the forums and nice haul by the sounds of it.

    Thankfully the PDP-11 series was not mainframe class, just minicomputers.
    A lit RUN light is good for the most part because that means nothing immediately caused the CPU to halt like bad ram or ROM. The lack of a console might come down to just cabling.
    [Need something to waste time on? Click here to visit my YouTube channel CelGenStudios]
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    = Excellent space heater

  4. #4
    Join Date
    Feb 2011
    Salisbury Maryland


    Not that famiyure with the 44 but spent a lot of time with its ancestor the 34, welcome to the world of Unibus! Down load the 11/44 manual and look at the card layout in the system. You have to have active cards or grant cards in every slot or else the system hangs. Sometimes when they pull this stuff out of service they yank cards and leave open slots and on Unibus that’s a issue.
    Would assume the system once working will give a boot prompt and by escaping that you can bump back into ODT that will allow you to look at and poke addresses in the system and do things like load loop programs and the like for testing.
    What type of storage drives were with it?

  5. #5


    Sorry for the delay in replying everyone, I had to wait for the thread to get approved and then it took some time for me to get notification that it did.

    I currently took apart the main power supply for a full rebuild, I will document that in a video and video hopefully sometime this week.

    I managed to get quite a lot of PDP-11 stuff- lots of unibus cards for the rack mount version. I also have lots of full devices including TU80, bunch of RS02s, some HDD arrays (mostly MFM but some SCSI), a big 10?" platter drive, three RL01s, tons of other goodies that I have yet to figure out what they are. I also got a bunch of VAX systems and related networking supplies for them.
    I am planning on selling some of it as a reasonable cost to finance the restoration of a select few of these parts.


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