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Thread: PDP-11/23+ hang right after booting up

  1. #1

    Default PDP-11/23+ hang right after booting up

    Hello everyone,

    I'm new here and nice to meet you all.

    Currently I have trouble with a PDP-11/23 machine that's used as the core computer of a Froude Consine automobile control system.

    The problem is when I hooked up the serial cable to Port 1 of the serial board (DLVJ1) of the PDP-11/23+ machine, I expected it to send out data to a PowerTem Plus terminal on my (modern) computer when it's booting up. Unfortunately it just stuck at the blank screen and hang! Actually I could play with it last week and I have no idea why it refused to serve me from 3 days ago.

    Then I spent time google for solutions but only found documents for newer versions of the machine that cannot help me much. My machine includes a KDF11-AA processor board that doesn't have LEDs for diagnostic like the KDF11-BA or newer.

    My knowledge and experience with this old guy is very limited and I wish someone here to show me how to solve out the problem. Even small hint or tip is appreaciated!

    Thanks a lot.

    Peter
    Last edited by PeterChu; April 8th, 2009 at 03:10 AM. Reason: Correct machine model: plus -> non plus

  2. #2

    Default

    Is everything set up exactly the same as last week? Same port, cable, serial port settings, etc.?

    If you halt the CPU, do you get the ODT prompt?

    You should be able to find a manual for the KDF11 on Manx.
    Last edited by cosam; April 8th, 2009 at 01:31 AM.

  3. #3

    Default

    Hi cosam,

    Thanks for your reply. Everything is exactly the same as last week, including cable and jumper settings. When I flipped the "Enable Halt" switch off then there were no prompt but charaters out to the ODT. They started by the @, such as @D, @P .... and then reacted when I keyed in from the keyboard. But when I switched back the "Enable Halt" switch then the system hanged immediately and refused to interact with the keyboard or generate any character on the ODT.

    I suspect there's something wrong with the DLV11-J board, specifically the serial port 1 used to connect with the serial cable and will try to replace the ICs related to this port. I have no schematic or userguide and this will be actually just a trial and error way to work around the problem.

    Would you please give me some ideas/comments? Thanks for the helpful resources. I will dig into it now.

    PS: I just edited the information. My system is actually a PDP-11/23 model, not the "Plus" model.
    Last edited by PeterChu; April 8th, 2009 at 03:32 AM.

  4. #4

    Default

    Quote Originally Posted by PeterChu View Post
    When I flipped the "Enable Halt" switch off then there were no prompt but charaters out to the ODT. They started by the @, such as @D, @P .... and then reacted when I keyed in from the keyboard.
    Not sure what you mean by that. The "@" is the ODT prompt, although it's usually preceded by an address. Are the 'D', 'P' and so on somehow "appearing" at the prompt? Can you execute any ODT commands from your terminal? How about if you hit reset whilst halted?

    Quote Originally Posted by PeterChu View Post
    I suspect there's something wrong with the DLV11-J board, specifically the serial port 1 used to connect with the serial cable and will try to replace the ICs related to this port.
    I'm not familiar with the DLV11. I don't suppose there's any way to use another port for the console? It would be a lot less hassle to source a replacement SLU module than trying to repair the existing one when you don't know what (if anything) is wrong with it. I think the schematics are however available via Manx (link in previous post).

  5. #5

    Default

    Hi cosam,

    Please let me explain it a little bit more. First I turn on the "DC ON" (the two other switches "ENABLE HALT" and "LTC ON" also on), the machine run for a while, both the two LEDs in the front on. But right at the moment it's expected to send out data to the ODT, it hung! The two LEDs were still on, but the system hung. I could see the icon at the left bottom corner of the terminal turned to red to indicate that.

    Then I switched down the ENABLE HALT switch, then the system generated some characters beginning with the @ on the screen. I was aware that the right LED according to the system not always on, but flashed (blinked). It only generated characters on the ODT when the LED on, then it stopped when the LED off, and then continued ... I suspected that it output the program on the bootstrap, but in a format I cannot recognize.

    Sometimes it kept generating the characters continuously, sometimes I need to "trigger" it by pressing on the keyboard of my PC.

    Then I turn the ENABLE HALT on again, then the system hung again.

    I've just found out the schematic of DLV11J at the following site and will give it a try if necessary because I cannot afford a new spare card.
    http://www.aceware.iinet.net.au/acms...BookId=99,981&

    PS: A quick search on Manx turned out to a great thing - a whole schematic of the machine.
    http://vt100.net/manx/details/1,10458
    Thanks again for the great resource!
    Last edited by PeterChu; April 8th, 2009 at 04:37 AM.

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