[vcf-midatlantic] Schematic work needed

RETRO Innovations go4retro at go4retro.com
Wed Aug 29 02:56:49 EDT 2018


On 8/29/2018 1:15 AM, Evan Koblentz via vcf-midatlantic wrote:
> I need someone to make two (relatively simple) schematics for me. One 
> is the IBM card for the Lego kit, and one is the Lego interface box.
>
> Here is one side of the IBM card:
> http://snarc.net/lego_ibm_1.jpg
>
> Here is the other side:
> http://snarc.net/lego_ibm_2.jpg
>
> Here's a picture of the top of the interface board:
> http://4.bp.blogspot.com/-DGOlTkGXj_Q/U8-T2uBG5iI/AAAAAAAAATY/7ra6gVkSKg8/s1600/LEGO_ControllerBoard_Top.jpg 
>
>
> Here's the bottom of the interface board:
> http://lukazi.blogspot.com/2014/07/lego-legos-first-programmable-product.html 
>
>
> Here's a document Dan R. made of the board a year or two ago:
> http://snarc.net/9750.png
>
> Now here is the catch..... I absolutely MUST have a complete, perfect, 
> finished schematic of the IBM card and the interface board by a week 
> before Maker Faire -- so let's say the deadline is Friday, Sept. 14.

Do you have a backup plan?  I say that because I professionally feel 
that creating a working and tested schematic within your timeline is 
going to be nearly impossible.

  * The first board is two sided, and those typically need to be
    unsoldered to ensure all traces under the ICs have been mapped. One
    can try to use a multi-meter, but there are pitfalls
  * Even if the schematic is doable, there's no way to truly ensure it's
    perfect unless one make a spin of the PCB, populates it, and tests
    it.  unless one wants to spend $250.00, it takes about 2 weeks to
    spin a PCB.
  * Though the other board looks to be single sided, all of the items on
    the board must be described and validated.  The toroids in the
    center and right seem particularly problematic, as one needs to
    determine the uH, turns, and such of the items in order to be
    perfect.  As well, those TO-220 transistors (or maybe they are FETs)
    sandwiched in between the connectors need to be desoldered or
    somehow moved so the markings can be read.  The LEDs need to be
    scoped to determine their mA rating, etc.

I'm not trying to rain on the parade, but I do want to inject some 
realism into the request timeline.  Doing such a reverse engineer will 
probably take a month or so, assuming someone squeezes it into their 
normal workflow and they do this regularly.

Someone already made a schematic of the Apple II card:
> http://lukazi.blogspot.com/2014/07/lego-legos-first-programmable-product.html 
>

Regrettably, it looks like the Apple uses a different schematic 
completely (It uses a VIA instead of the IBM PC discrete TTL) and so 
this schematic will not help.

Jim


-- 
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