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Thread: Atex PDP-11/34

  1. #1
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    Default Atex PDP-11/34

    Hey everyone, I started a thread about this computer a while ago and if you want some context about it you can go here: http://www.vcfed.org/forum/showthrea...Atex-PDP-11-34

    Anyways, I am at the stage where I now have to troubleshoot all of the boards, I already had done everything power supply related (Cap refroming etc). When I power the machine on with the CPU board only, I get the DC ON light to glow, and the run light blinks three times. I don't have a serial card for the machine and the cpu board doesn't look like it has a serial port. So what do I do make the computer show any signs of life apart from the front panel?

    Thanks everyone!

  2. #2
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    Since the CPU board has a J-11 on it, it will have built in ODT, which if you can figure out how to configure the board to set the power up mode bits (in the configuration regsiter) appropriately, the CPU will enter it at reset. ODT expects to see a DLART (DC319-AA) serial port located at the standard console address of 17777560. If you can not determine if one of the Atex boards contains a console serial port, you can obtain an appropriate Unibus board to use while you are testing your system.

  3. #3
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    Looking at your other thread, I'm still not clear on what you have there.

    Does this unit have any DEC boards in it? What are they?
    Does it have a front console, with the octal keypad, etc? (The "Programmer's Console")
    Did you get the power supply working?

    I have other questions, but they depend on answers to the above.
    Some more pics would help...

  4. #4
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    Would the grey connector be it? It has 26 pins

    unnamed.jpg

  5. #5
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    Can I suggest (as has been pointed out above) that we get a complete inventory of the system first and then some detailed photographs/scans of the boards second. You will have to store the scans externally and point us to them (as VCFED 'downgrades' the images to the point of being unusable).

    Unless anyone knows specifically about the card, we will be all guessing as to whether the 'grey connector' is a serial port or not.

    The give-away will be the presence of any RS232 buffers - and then we can follow the PCB tracks to whichever connector they go to...

    Dave

  6. #6
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    Ok here goes... I had bought this PDP 11 from ebay im and was told that it had not been powered on in ages, I was also told that this was an atex system. I didn't care then about the fact that it was an atex machine, but I sure do now

    Here are some photos with descriptions of them. https://imgur.com/a/bBqKuAn

    If you have any questions about the PC or need more photos I will be happy to provide them.

    Thanks everyone!

  7. #7
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    I believe that the grey connector that I was previously talking about, is the serial port due to the fact that the first two IC that they went to were quadruple line receivers and octal bus transceivers. Datasheets below

    https://pdf1.alldatasheet.com/datash...C1489ANE4.html

    http://www.ti.com/lit/ds/symlink/sn54ls245-sp.pdf

  8. #8
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    Excellent,

    The 1489 is the receiver, but I would expect a 1488 transmitter (if it was 'true' RS232). It may not be of course.

    I would next use a multimeter (set to a low resistance range) to work out which pins of the grey connector are wired to which input pins of the 1489 buffer. These are the potential inputs (plus handshake signals). I would also work out where the other pins are connected to (as far as you can).

    Is there a 40 pin device identifiable as a UART? If so, you can trace the transmit and receive signals from the actual UART. DEC generally didn't use hardware handshake signals, so transmit and receive is all that is generally required to get a working serial port. We have to identify the correct baudrate and serial configuration though. This would be much easier if you can identify the UART itself.

    What we are aiming for is to get the '@' prompt on a terminal/PC when you hit the 'HALT' key...

    Dave

  9. #9
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    Of course, the other 'simple' way of looking at this is "is there a cable/connector anywhere that came with the equipment that looks like it plugs into the grey connector?

    EDIT: I looked on the original e-bay post - but see there is nothing plugged into the gray connector on the CPU card. There is something plugged into the blue connector. ANy idea where this went? I further notice two (2) small cards on the chassis with 25 way D male connectors. Can you take a close-up photograph of these please (or let us know what devices are on them)? They look suspiciously like asynchronous adapters to me???

    This is all exciting... You may not think so at the moment though!

    Dave
    Last edited by daver2; July 1st, 2019 at 12:36 AM.

  10. #10
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    The panel board marked Workstation III/LAN mentions Thinnet and AUI, which are commonly used to describe Ethernet cable variants. If you get an AUI to Twisted Pair adapter (i.e. RJ45 connectors), you might be able to attach to a switch that supports 10Base-T. Supposedly the DP83900 chip on the board is similar to the 3Com 3c90x series Ethernet interfaces. You would need an appropriate device driver to even use the Workstation III/LAN board, which might be difficult indeed to find, but there appear to be PROMs on the board that might contain some code.

    I note that board is also marked as having serial ports on it. There is a 165520 which is a DUART chip.

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