[vcf-midatlantic] A little electronics hack

Evan Koblentz evan at vcfed.org
Mon Sep 30 09:13:16 EDT 2019


>> If you're interested in investigating further if you point us to
schematics we can give suggestions.

I am giving the box to Neville in early November (don't want to risk it not
working before the Brickfair NJ event the first weekend of that month). He
agreed to my request to make a schematic of it.

The next step will be to have someone else take his schematic, build one,
and send it back to me for testing. That'll prove that the box can in fact
be built from just the plans. After that I'll post it on my website.

A possible third stage would be to make modern improvements, if any ideas
stand out.

I'm only interested in the function, not in replicating the physical case.
But what I would avoid is replacing the vintage computer with a
microcontroller. I'm all for a better interface but strictly against some
non-vintage computer experience.




On Mon, Sep 30, 2019, 8:43 AM David Gesswein via vcf-midatlantic <
vcf-midatlantic at lists.vcfed.org> wrote:

> > >> It's called a 'crowbar' circuit.  Prevents things from burning up.
> >
>
> What I normally called a crowbar circuit is the overvoltage protection
> where it intentionally shorts the output of the power supply. This sounds
> more like over current protection.
>
> > What are common reasons why those stop working? Neville and I didn't see
> > any obvious signs of damage to it.
> >
> Either component value shift or failed component. You indicated that it is
> driving the motors better than it ever has. It may also be your motors
> are a heavier load than it was intended to drive.
>
> If you're interested in investigating further if you point us to schematics
> we can give suggestions.
>
>
> > On Sun, Sep 29, 2019, 1:56 PM Mike Loewen <mloewen at cpumagic.scol.pa.us>
> > wrote:
> >
> > > On Sun, 29 Sep 2019, Evan Koblentz via vcf-midatlantic wrote:
> > >
> > > > Neville noticed something that I wouldn't have. The circuitry
> contains a
> > > > safety mechanism to shut off all power if the current jumps too high,
> > > such
> > > > as a kid inserting a paper clip. There's probably a technical name
> for
> > > that
> > > > but I do not know it. Anyway, for unknown reasons this circuit was
> > > kicking
> > > > in! He jumped it with an equal-length wire. :)
> > >
> > >     It's called a 'crowbar' circuit.  Prevents things from burning up.
> > >
> > >
> > > Mike Loewen                             mloewen at cpumagic.scol.pa.us
> > > Old Technology
> http://q7.neurotica.com/Oldtech/
> > >
>


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