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PDP-8/E Omnibus unexpected behavior

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    #16
    Originally posted by DougIngraham View Post
    TP4 is the earliest point to latch the address for the next memory cycle.
    That's why I suggested it. But it doesn't reflect memory cycles that the front panel hasn't started yet, which has been pointed out.

    Knowing the issue is with E19 you will also want to see if you can find the reason E19 failed. A 7416 is a high voltage open collector inverter. Each output can sink 40 ma according to the data book. I wonder if the wrong bulb was used or if a bulb shorted or something like that.
    My theory is that there's something wrong with the ground run for E19. Perhaps a bad solder joint or a cracked/cut trace?

    Vince

    Comment


      #17
      Doug,

      Thank you for all of your help.

      I will try gating off of SOURCE_H rather than TP4_H.

      I will replace E19 and see how is goes.

      I replaced all of the lamps on my front panel with AML-7367 from Advanced Micro Lites in Illinois ( https://www.advmicrolites.com/incandescent/ ).
      Please see my post here ( https://www.vcfed.org/forum/forum/ge...98#post1226198 ) for a comparison between this bulb and the bulbs that were already in my PDP-8/E. I have spares if you need some.

      Thanks again,

      Mike
      I have been a PDP-8 fan since the early 70s. My milk machine is a PDP-8/L w/4K core & an ASR-33. Paper Tape for storage. I have a PiDP-8/I, a PiDP-11/70 and a real live PDP-8/E. I"m always looking for more stuff for the PDP-8/E

      Looking to buy/acquire RX8E/RX28, RX01/RX02, TU56, TD8E, TC08, RK05, PC08, PC8E and any other PDP-8 equipment and boards.

      Comment


        #18
        Originally posted by vrs42 View Post

        That's why I suggested it. But it doesn't reflect memory cycles that the front panel hasn't started yet, which has been pointed out.



        My theory is that there's something wrong with the ground run for E19. Perhaps a bad solder joint or a cracked/cut trace?

        Vince
        I will check out the ground run for E19. Thanks for everything.
        I have been a PDP-8 fan since the early 70s. My milk machine is a PDP-8/L w/4K core & an ASR-33. Paper Tape for storage. I have a PiDP-8/I, a PiDP-11/70 and a real live PDP-8/E. I"m always looking for more stuff for the PDP-8/E

        Looking to buy/acquire RX8E/RX28, RX01/RX02, TU56, TD8E, TC08, RK05, PC08, PC8E and any other PDP-8 equipment and boards.

        Comment


          #19
          Originally posted by vrs42 View Post
          That's why I suggested it. But it doesn't reflect memory cycles that the front panel hasn't started yet, which has been pointed out.
          I figured as much and TP4 is the obvious place to latch the address if you are a memory board. Clearly not quite what he was looking for here. Looking forward to hearing if SOURCE does what he wanted. It still wont latch on the Load Addr switch press which probably means it still won't be exactly what is wanted.


          Doug Ingraham
          2nd owner of Straight 8 SN1173
          5 other PDP-8's including an 8/i and a DECSet 8000
          SOL-20

          Comment


            #20
            The address information is permanent on the bus. So you just need a driver for the LED, you don't need to latch anything.
            WTB: Case for Altair 8800 ...... Rolands Github projects

            Comment


              #21
              The PDP-8efm Maintenance Manual volume 1 pp 3-96 thru 3-106 has a very detailed description of how the programmer's console logic operates.

              Comment


                #22
                Originally posted by DougIngraham View Post
                I figured as much and TP4 is the obvious place to latch the address if you are a memory board. Clearly not quite what he was looking for here. Looking forward to hearing if SOURCE does what he wanted. It still wont latch on the Load Addr switch press which probably means it still won't be exactly what is wanted.

                As long as the the address latched is the address of the data represented on the MB lights I will be happy. It doesn't have to be when ADDR LOAD is pressed but can be after DEPOSIT or EXAM is pressed.

                Thank you.
                I have been a PDP-8 fan since the early 70s. My milk machine is a PDP-8/L w/4K core & an ASR-33. Paper Tape for storage. I have a PiDP-8/I, a PiDP-11/70 and a real live PDP-8/E. I"m always looking for more stuff for the PDP-8/E

                Looking to buy/acquire RX8E/RX28, RX01/RX02, TU56, TD8E, TC08, RK05, PC08, PC8E and any other PDP-8 equipment and boards.

                Comment


                  #23
                  Originally posted by Roland Huisman View Post
                  The address information is permanent on the bus. So you just need a driver for the LED, you don't need to latch anything.
                  The latch is specifically to handle the fact that the address is the next address not the current address and to handle any transitions on the bus that don't need to be displayed.
                  I have been a PDP-8 fan since the early 70s. My milk machine is a PDP-8/L w/4K core & an ASR-33. Paper Tape for storage. I have a PiDP-8/I, a PiDP-11/70 and a real live PDP-8/E. I"m always looking for more stuff for the PDP-8/E

                  Looking to buy/acquire RX8E/RX28, RX01/RX02, TU56, TD8E, TC08, RK05, PC08, PC8E and any other PDP-8 equipment and boards.

                  Comment

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