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Thread: Build your own PDP 8I, Part 4..

  1. #161
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    Hi All;

    I got most of the Ground Wires wired up, I still need to solder some of them to the ground cap connection for a absolute solid ground connection..

    As I am NOT going to solder in my Wire-wrap Sockets for my Power and Ground connections..

    Next will be the +5 Volts Connections..

    Also I have put in some sockets for my Memory, which will most likely be 2102's Ram.. I may put in the 7489's for first checking of the circuitry, before switching to the 2102's..

    THANK YOU Marty

  2. #162
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    I'm soldering in my sockets, but then I'm a belt-and-suspenders kind of guy.

  3. #163
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    Hi All;

    "" I'm soldering in my sockets, ""

    I cannot afford to do that, that would be too many sockets, that I could not use on anything else..

    A friend of mine soldered in some Connectors, and both the Connectors and the Board are now no good, since I cannot take them out without a flame thrower, and that would Ruin the Board..

    THANK YOU Marty

  4. #164
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    Hi All;

    I got all of the Power and Ground wired up..

    I need to next figure out which schematic, that I need to use, and then get started on it..

    THANK YOU Marty

  5. #165
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    I have made a start on my board also.

    I have the 'disadvantage' in that I am having to write the construction/assembly manual as I go...

    Anyhow, I have installed the decoupling capacitors - with the intention of soldering them in this week. I will then move on to the six diagnostic LEDs on the small prototyping area and then the IC sockets.

    >>> I have a design for a PDP-8 using 2N7000 transistors and resistors.

    Before I started on the LD12 PCB - I had the idea of building a PDP-8 out of purely 2N7000 transistors and resistors. I got as far as buying a load of components and prototying up the circuits (latches, adders, multiplexers etc.) and then in putting together the LOGISIM model. This started to work - but then 'broke' LOGISIM as the circuit became more and more complex; to the point of it refusing to simulate the logic at all. That was when I decided to go back to the LD12 and TTL idea (as we knew that would work). Who knows, I might go back to the PDP-8 out of RTL (resistor transistor logic) at some time in the future?

    Dave
    Last edited by daver2; July 22nd, 2019 at 02:20 AM.

  6. #166
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    Hi All;

    Dave, "" I will then move on to the six diagnostic LEDs on the small prototyping area and then the IC sockets. ""

    That Sounds like a good Idea !! Thank You for the suggestion..

    THANK YOU Marty

  7. #167
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    This is based upon what I have seen on the original at https://retrobrewcomputers.org/n8vem...7/100_3908.JPG.

    I will add this detail to my construction/assembly manual and the schematic/BoM. It requires a 7406 to be installed in the bottom row of the 'J' chip column. Not sure exactly which socket until I get home.

    Dave

  8. #168
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    Hi All;

    Dave, I'm putting in 6 Green Rectangular Led's, as they seem to fit the space better, (and that is what I have in rectangle) and I am using an R-Pack instead of Individual Resistors..

    THANK YOU Marty

  9. #169
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    Hi folks,

    I'm a bit behind you... I need to order parts. However, I just purchased a Gardner-Denver wire wrap gun on eBay:

    https://www.ebay.com/itm/OK-Industri...53.m2749.l2649

    I made an offer for $28.30, plus the shipping he was asking for was $11.70, so my total was $40.00. That's *much* better than the few hundred $$$ I was looking at with the new manual tool I found on DigiKey.

    I had sent a message to a few different Sellers, asking them to verify if they were offering a wire wrap bit that was correct for AWG 30 wire, and this fellow responded that he checked the part number and it was correct. So, here's hoping for the best!

    Dave, are you incrementally updating the construction/assembly manual on your Google Drive? Or should I wait a bit to get the benefit of your experience?

    Also, are you willing to share your KiCAD package? That would save me all the effort of entering all that in for myself.

    Thanks!

    smp

  10. #170
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    Quote Originally Posted by smp View Post
    Hi folks,

    I'm a bit behind you... I need to order parts. However, I just purchased a Gardner-Denver wire wrap gun on eBay:

    https://www.ebay.com/itm/OK-Industri...53.m2749.l2649

    I made an offer for $28.30, plus the shipping he was asking for was $11.70, so my total was $40.00. That's *much* better than the few hundred $$$ I was looking at with the new manual tool I found on DigiKey.
    If it all works out, that's a great price. However, you need to add a manual unwrap tool to your arsenal, if you don't have one. Mistakes will be made.

    OK, Vector, Radio Shack, etc. are all pretty much the same. I like the double-ended OK one as it serves as both a wrap and an unwrap tool.

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