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Thread: Need help with 11/23 system

  1. #1

    Default Need help with 11/23 system

    System consists of LSI 11/23 (M8186), MSV11 (M8059KF), DLV11-J (M8043), RQDX3AA (M7555), and BDV11. These are in what was a MicroVAX II box. Thanks to help on the forum I burned a set of 2716 EPROMs as KDF11-BJ ROMs. Using PUTR I created what I hoped would be a bootable RT-11 disk for the RX50 drives. Everything seemed to be working OK other than the fact that the RT-11 disk is faulty. The computer would get to the point of attempting to read the disk. If I left the disk out it would look for further DU devices and finally take me to a point where I could bring up the menu with several option. So then I got the bright idea of connecting a 3.5 inch floppy drive as an RX33 so I then made an RX33 disk. When I connected the 3.5 inch drive in place of the RX50 I neglected to use a cable with the "twist". Don't know if that made a difference but from that point on the system has been flakey. I went back to the RX50 drive but now I get unstable behavior. Every time I start up the system it gets part way through the startup. Did manage to have it get as far as trying to read the disk but finally crashed. Also got it to get to that point without the diskette in place and it attempted to look for a second DU drive but then crashed. I have included various shots of what went on. Any help would be greatly appreciated.

    Thank you!

    -Al

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  2. #2
    Join Date
    Apr 2017
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    Default

    Try without RQDX.

    Peter

  3. #3
    Join Date
    May 2011
    Location
    Liverpool, England
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    Also you could try taking each card out one by one and "exercising" any DIP switches and using a multimeter check they are as they should be i.e. on or off, I've had issues with DIP switches on DEC boards myself. Also reseat any pluggable IC's.

  4. #4

    Default

    Removing the RQDX board didn't change anything. Results were variable as ever. I did make sure that the boards are firmly in place. I should reemphasize that the change in behavior from good to bad occurred when I tried connecting the 3.5 inch drive in place of the RX50. From then on I got this behavior even though I went back to the RX50.

  5. #5
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    So at least it seems not to be cause by the experiments with the RX33. It would have surprised me that this could cause any damage. It's all open collector signals. So next question, do you have any spare parts to run a minimal system (you could try without the BDV, just CPU, Memory and DLV11J) to isolate the card that causes the problem. Not very useful, but you could then try to boot RT-11 via a TU-58 emulator, the one from Jöerg includes a downloadable bootstrap loader. BTW which backplane are you using? Or perhaps the power supply is flakey?

    Peter

  6. #6

    Default

    As mentioned above, system is in a Microvax II box, BA23. Backplane is H9278 and power supply is H7864. I did try the 3.5 inch drive again, this time with a "twisted" cable. In those instances where the system gets that far I can hear it trying to read the drive but comes up with an error as with the RX50. I am just assuming I have badly prepared the floppies. Of course most of the time the system crashes at some point, sometimes sooner and sometimes later. Before I took out the Microvax boards I did prepare floppies with the diagnostics for the Microvax and was able to run them OK. Of course now there is a different set of boards but the power supply and backplane is the same. Another point, the memory board I have is a M8059KF which presumably has 128 K of memory but the startup diagnostic says 256K of memory.
    Where do I find the information on the TU-58 emulator?

    Many thanks!

    -Al

  7. #7
    Join Date
    May 2011
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    Default

    Did you try what I suggested?

  8. #8

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    In one of your picture it looks like the computer halts due to a memory problem. The memory test in the bootstrap is probably not that exhaustive. You should run a proper maindec for several minutes to rule out a memory problem.

    I think PDP11GUI can be quite useful to load binary programs into the machine. You can find appropriate diagnostics (CPU / Memory etc) and load them in absolute binary format and hit go.

    TU58FS (A variant of the TU58 emulator stuff) works fine if you have a secondary serial port. It has to be setup at address/vector 165000/300.

    Make it a very minimal system with memory, cpu and serial ports. Leave out the RQDX controller until you know that everything else works. It is very unlikely that you fried anything in the floppy controller since it is OC as cbscpe writes.

    Some links:

    http://retrocmp.com/tools/pdp-11-diagnostic-database
    http://retrocmp.com/tools/tu58fs
    http://retrocmp.com/tools/pdp11gui

  9. #9
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    Apr 2017
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    Switzerland
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    Just to make sure, you only have one additional terminator. In other words not both, the terminators in the H9278 backplane and the BDV11 at the same time. Also does the BDV11 have all ECOs applied? With the DLV11J set with the correct jumpers channel 0 will have the address/vector required for TU-58 (it actually is the factory setting with channel 3 being the console)

  10. #10

    Default

    Thank you for additional answers. I will have to take time to digest this information.
    PG31-Yes I checked those things out.
    cbscpe-I do have both the H9278 and BCV11 terminators in place. Will have to see which is easier to remove.
    I will have to look over the retrocmp websites and see if I can make sense of them!
    Will get back after investigating these things.

    Thank again.

    -Al

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