[vcf-midatlantic] Schematic work needed

[Chris Fala]

Ha, depopulate! You just scared away most people! :-) Desoldering is a
skill I have yet to see demonstrated competently by many people, especially
on YouTube.




On Wed, Aug 29, 2018 at 8:25 AM systems_glitch via vcf-midatlantic <
vcf-midatlantic at lists.vcfed.org> wrote:

> I'd had the ISA card in the shop for a while and didn't get around to
> mapping it out. I've explained to Evan that it's not a trivial process.
>
> I offered to depopulate the board and send it off to Mile High Test for a
> scan + conversion to Gerbers, which are guaranteed to be 100% accurate, but
> that costs around $200-250. It's the same process I've used to reproduce
> various Ohio Scientific and S-100 boards.
>
> Thanks,
> Jonathan
>
> On Wed, Aug 29, 2018 at 2:58 AM RETRO Innovations via vcf-midatlantic <
> vcf-midatlantic at lists.vcfed.org> wrote:
>
> > 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
> >
> >
> > --
> > RETRO Innovations, Contemporary Gear for Classic Systems
> > www.go4retro.com
> > store.go4retro.com
> >
> >
>