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Thread: S100 Backplane Project.

  1. #1

    Default S100 Backplane Project.

    I'm almost finished with the backplane project, but
    I have a few questions first.

    For the fuses, I was wondering what the values are?

    I figure for the +/- 16VDC 3A should be enough.

    For the + 8VDC. This would be set above the current
    draw for all the PCB's on the bus. I'll start out at 10A
    or so... Or if someone has a recommendation...

    My other question is, what is the calibration procedure
    or purpose for the 2k pot ?

    BTW: The Mouser S100 connectors fit spot on! Everything aligns
    fine, the pins are long enough for this thick sturdy PCB & the
    mounting holes match up. At 8 bucks or so per connector, not bad.
    The only thing is the slot tabs are not gold plated.


    I purchased a new digital camera for the girlfriend (an x-mas gift) So
    I took it out and played with it. Here's some pic's of the backplane
    board and my Imsai.

    http://home.mchsi.com/~litterbox99/temp/ims1.jpg

    http://home.mchsi.com/~litterbox99/temp/ims2.jpg

    http://home.mchsi.com/~litterbox99/temp/ims3.jpg

    http://home.mchsi.com/~litterbox99/temp/ims4.jpg

    http://home.mchsi.com/~litterbox99/temp/ims5.jpg

    FWIW: You may use any/all pic's I post for other purposes.

    Thanks !

    Todd

  2. #2

    Default

    Hi! Thanks Todd! Your photos look great! Excellent work!

    The pot on the S-100 backplane is for active termination of the S-100 pins. Use your VOM to measure a signal pin in the S-100 bus (without any boards installed) and adjust the pot so the voltage is 2.7V. Then the backplane is actively terminated in the middle region between high and low.

    Beautiful work! Very nice to see!

    Thanks and have a nice day!

    Andrew Lynch

  3. #3

    Default

    IMS2.JPG shows a vintage computer, and if I am not mistaken, 4-track tapes (now that's vintage).

  4. #4

    Default

    Quote Originally Posted by litterbox99 View Post
    I'm almost finished with the backplane project, but
    I have a few questions first.

    For the fuses, I was wondering what the values are?

    I figure for the +/- 16VDC 3A should be enough.

    For the + 8VDC. This would be set above the current
    draw for all the PCB's on the bus. I'll start out at 10A
    or so... Or if someone has a recommendation...

    My other question is, what is the calibration procedure
    or purpose for the 2k pot ?
    Hi! I would start the fuses at 1A for the +/- 16VDC and 3A for the 8VDC. Depending on what you are using that should be sufficient. If its not enough consider bumping them up a notch.

    If you draw much more than that with relatively recent technology then something is wrong. You can adjust to circumstances though. Also using SMPSUs helps since they have built in current limiters.

    Thanks and have a nice day!

    Andrew Lynch

  5. #5
    Join Date
    Jan 2010
    Location
    Central VA
    Posts
    4,303

    Default

    With my bare minimum S-100 boardset, using vintage hardware, I draw around 4 A from the +8V line. That includes a Cromemco ZPU, Cromemco 4FDC and SC Digital 16K RAM board. The +/- 16V lines are never taxed beyond 250 mA, but the only thing that uses them is the 4FDC's serial port. Sizing the +8V fuse to your power supply's capabilities might be more prudent than basing it on current card consumption.

  6. #6
    Join Date
    Jul 2009
    Location
    Curwensville, PA
    Posts
    480

    Default

    Very nice work litterbox99. Can you identify the connector you used for P1? I haven't found one that is the right pitch.

    Thanks,
    Kipp

  7. #7
    Join Date
    Oct 2008
    Location
    San Ramon, CA
    Posts
    251

    Default

    Todd I generally allow about 1-1.5A's per card slot. Hopefully your power supply is above that. The -16V is next to nothing, 1A should be fine. I use 3A on the +16,again way over kill I'm sure. It's probably more important to have correct/lower fuses on the extender board because that's the one you will normally be putting new boards into first. I use Jameco resettable fuses (#199938 and 200062) for these.

    Nice pictures BTW, I used your picture on the S100Computers site listing the board. Hope that's OK.
    John

  8. #8

    Default

    Quote Originally Posted by douglas_goodall View Post
    IMS2.JPG shows a vintage computer, and if I am not mistaken, 4-track tapes (now that's vintage).
    Yeah that's my 8-track stereo... it's quadraphonic ! You can see a bit of it in the upper left
    corner of IMS1.JPG

    Here's another pic.

    http://home.mchsi.com/~litterbox99/graphics/8track.jpg
    Last edited by litterbox99; December 6th, 2010 at 02:54 PM.

  9. #9

    Default

    Quote Originally Posted by kyeakel View Post
    Very nice work litterbox99. Can you identify the connector you used for P1? I haven't found one that is the right pitch.

    Thanks,
    Kipp

    If you go here;

    http://n8vem-sbc.pbworks.com/w/brows...00%20backplane

    Theres a few files with the part numbers you need.

  10. #10
    Join Date
    Apr 2010
    Location
    Arlington, MA, USA
    Posts
    192

    Default

    Quote Originally Posted by litterbox99 View Post
    Yeah that's my 8-track stereo... it's quadraphonic !
    Sorry to prolong the off-topic stuff, but that stereo must be from the 1970s. The design of the front panel is definitely classic. You really should get a leisure suit to wear when listening, however.

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