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  1. Replies
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    Thanks for the 'bump'. I completely missed your...

    Thanks for the 'bump'. I completely missed your post. Been busy over in DEC PDP-8 land recently (although I did pull my MK14 stuff out of the storage box yesterday would you believe!).

    >>> Can you...
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    >>> This Explains why my friend is using the...

    >>> This Explains why my friend is using the 2N7000 in numerous places , I think it is for LED display purposes, on the 8080 Diode Transistor unit..

    And I have a design for a PDP-8 using 2N7000...
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    Nice detective work! Dave

    Nice detective work!

    Dave
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    Been thinking about the front panel issue. Some...

    Been thinking about the front panel issue. Some further thoughts:

    The LD12 is based upon a PDP-8/I not a PDP-8/L. I got my letters and numbers mixed up at one point - the i and l look very similar...
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    493

    You say above that you replaced C51 with an...

    You say above that you replaced C51 with an electrolytic. The parts list calls for a low leakage electrolytic - or a tantalum.

    If the capacitor is too leaky - it may not charge up enough to...
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    smp: Will send you the KiCAD files when I get a...

    smp: Will send you the KiCAD files when I get a few minutes. It is unlikely to be this weekend though. We may have to do this 'incrementally' as I don't know exactly which files you will need. This...
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    Based upon your last post I would check the...

    Based upon your last post I would check the following:

    R15 (1k pull-up to +5V). The 7407/7417 are open collector devices. So if this resistor is open circuit - or the PCB track damaged - then the...
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    If the reset circuitry doesn't work - then there...

    If the reset circuitry doesn't work - then there is no chance of the PET working.

    Solder a normally open pushbutton either across C51 - or between pins 7 and 1 of UD16 (555).

    Under normal...
  9. Replies
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    Monty, I like your optimism :-)! I am not...

    Monty,

    I like your optimism :-)!

    I am not particularly bothered about the microcoded instructions to be honest. Since I am emulating the machine at the microcode level, once I get the microcode...
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    As Frank has pointed out, the MK36000 device is...

    As Frank has pointed out, the MK36000 device is not as simple as potentially other (EP)ROMS are becuase of the address latch.

    It is all down to how your 29B works...

    I do have a copy of...
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    Nice going (again) Monty. I was just...

    Nice going (again) Monty.

    I was just re-reading the thread where you introduced yourself to VCFED. What progress you have made with all this Tek equipment in the meantime!

    I might have another...
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    Doing a bit more digging. I have used V5.1...

    Doing a bit more digging.

    I have used V5.1 firmware and V5 microcode in my 4052 emulator.

    The ROM code starts at 79F3 for V5.1 firmware.

    The ROM code starts at 7D0F for V4.something.

    If...
  13. Replies
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    I don't think the PET ROMs should be accessing...

    I don't think the PET ROMs should be accessing the upper bank of 16K RAM unless you have written some sort of (BASIC) program to do that.

    As a result, I think the active RAS and inactive CAS to me...
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    Maybe a good idea to read this thread...

    Maybe a good idea to read this thread http://www.vcfed.org/forum/showthread.php?18995-Saving-ROM-data-from-Tek-4052.

    There is a lot (and I mean a lot) of technical stuff on that thread regarding...
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    Found Jos's 4052/4054 diagnostic ROM pack thread...

    Found Jos's 4052/4054 diagnostic ROM pack thread at http://www.vcfed.org/forum/showthread.php?63025-Tektronix-4052-54-diagnostic-ROM-pack-remade.

    Need to look into your specific microcode halt...
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    Are you addressing RAM in the >16K range or not?...

    Are you addressing RAM in the >16K range or not?

    If not, the upper RAM CAS line will not be activated.

    The ROMs will be constantly accessing page 0, therefore the lower RAM CAS line will be...
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    Hi, About to run off to work, but will get...

    Hi,

    About to run off to work, but will get back to you at some point (or some of the other Tekies will)!

    If you hunt around on VCFED you will find a similar issue that we fixed on another 4052....
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    Start here with the documentation:...

    Start here with the documentation: http://www.bitsavers.org/pdf/osborne/executive/.

    Do you have any test equipment (e.g. multimeter, logic probe or oscilloscope)?

    Dave
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    Is the code for your Sim4-01 EPROMs on the web...

    Is the code for your Sim4-01 EPROMs on the web anywhere (or would you be willing to share them)? I might be interested in seeing if I can reconstruct the bits that have rotted! Multiple sets of eyes...
  20. Thread: Atex PDP-11/34

    by daver2
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    The problem you have is that you have too many...

    The problem you have is that you have too many variables...

    It is no good just plugging things in and hoping a serial port will burst into life. It won't...

    You need to get ODT working first....
  21. Replies
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    I read T701 here...

    I read T701 here http://www.zimmers.net/anonftp/pub/cbm/schematics/computers/pet/2001N/321446.gif

    Dave
  22. Thread: Atex PDP-11/34

    by daver2
    Replies
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    819

    Of course, the other 'simple' way of looking at...

    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...
  23. Thread: Atex PDP-11/34

    by daver2
    Replies
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    Excellent, The 1489 is the receiver, but I...

    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...
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    40 column non-CRTC is fine - it works OK with...

    40 column non-CRTC is fine - it works OK with that.

    The table that programs the CRTC is right at the beginning of the EPROM (apart from an initial 'JMP START', an ASCII 'V' and the version...
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    Yep, my program initialises the CRTC (in default...

    Yep, my program initialises the CRTC (in default 80 column mode) - so it should work with both non CRTC and CRTC PETs (providing they have 80 column displays).

    A 40 column CRTC PET would require...
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