[vcf-midatlantic] A little electronics hack

Evan Koblentz evan at vcfed.org
Mon Sep 30 14:15:13 EDT 2019


Big squiggly area in the center of the second (bottom) image.

On Mon, Sep 30, 2019, 1:48 PM Mark Whittington <markwhi at gmail.com> wrote:

>
> https://4.bp.blogspot.com/-DGOlTkGXj_Q/U8-T2uBG5iI/AAAAAAAAATY/7ra6gVkSKg8/s1600/LEGO_ControllerBoard_Top.jpg
>
>
> https://4.bp.blogspot.com/-6RLSsFHgMgY/U8-TzfBRxOI/AAAAAAAAATQ/NeiKlqHPevs/s1600/LEGO_ControllerBoard_Bottom.jpg
>
> Out of curiosity (and assuming I've found the right board images), do you
> happen to know where the circuit that Neville identified as faulty is on
> these images?  Also, I've found a couple of these units for sale in the US
> for ~$85 and in the UK for ~$50 that might be useful for backup or reverse
> engineering purposes.
>
> Cheers,
>
> -Mark
>
> On Mon, Sep 30, 2019 at 12:57 PM Evan Koblentz <evan at vcfed.org> wrote:
>
>> >> Looks like someone on this list has already done the legwork on this
>> as of 2016... https://www.glitchwrks.com/2016/09/12/lego-logo-interface
>> <https://www.glitchwrks.com/2016/09/12/lego-logo-interface>
>>
>> No - that's the card for connecting the computer to the interface box.
>> That schematic already existed and we didn't have the card, so Jonathan
>> (Glitch) built one for us. That is what you see documented. In the current
>> thread I am referring to the interface box itself. There is more info on my
>> personal website at http://www.mindsbeforethestorm.com/8bit_hardware.php.
>>
>>
>>
>> On Mon, Sep 30, 2019, 11:16 AM Mark Whittington <markwhi at gmail.com>
>> wrote:
>>
>>> Looks like someone on this list has already done the legwork on this as
>>> of 2016...
>>>
>>> https://www.glitchwrks.com/2016/09/12/lego-logo-interface
>>>
>>> On Mon, Sep 30, 2019 at 9:13 AM Evan Koblentz via vcf-midatlantic <
>>> vcf-midatlantic at lists.vcfed.org> wrote:
>>>
>>>> >> 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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