[vcf-midatlantic] Schematic work needed

systems_glitch systems.glitch at gmail.com
Wed Aug 29 11:46:18 EDT 2018

Sounds like we've got plenty of volunteers, then! :P


On Wed, Aug 29, 2018 at 11:45 AM alan--- via vcf-midatlantic <
vcf-midatlantic at lists.vcfed.org> wrote:

> It's two 8 bit opposing latches and some address decoding glue.  If one
> knew the port address, you could create the schematic blind and be 98%
> correct.
> Sent from my Verizon LG Smartphone
> ------ Original message------From: Kyle Owen via vcf-midatlanticDate: Wed,
> Aug 29, 2018 11:17 AMTo: vcf-midatlantic;Cc: Kyle Owen;Subject:Re:
> [vcf-midatlantic] Schematic work needed
> On Wed, Aug 29, 2018 at 10:05 AM RETRO Innovations via vcf-midatlantic <
> vcf-midatlantic at lists.vcfed.org> wrote:
> >
> > Many of the signals go under the ICs.  Sometimes, you can hold to a
> > light and see through the PCB and validate where they go, but other
> > times, I have missed wires connecting to more than 1 pin of the IC under
> > the IC.  Ohming, if applied verbosely for each signal around the IC
> > compared to each IC pin, should find all of them, but I don't think I
> > would promise 100% perfection without spinning a PCB and testing the
> > completed unit.
> >
> > Maybe everyone else is better at ohming out boards and the hidden
> > signals under ICs never bother anyone else, but I've gotten hit twice by
> > them on two different efforts.
> >
> Yes. If you do not completely ohm out each pin/component, I could very much
> imagine generating an incomplete schematic. The netlist generated by ohming
> out the board should have every pin on every component by the time you're
> done. If not, you've missed something. With some conditional formatting,
> it's possible to highlight possible errors like duplicate entries, too many
> pins per component, etc.
> Hidden traces are no problem *if* you are not relying on visuals, but
> rather the ohmmeter.
> And if you're using a Fluke, don't forget to hold down the yellow button
> when turning it on, lest you have it automatically power off while you
> attempt to ohm out the board. Ask me how I know... :)
> Kyle

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