[Coco] CoCo2 Strange Side Switches

[Louis Ciotti]

So looking at the photos, Here is what I show as it wired as:

Switch 1 (Furthest Rearward) VCC to CSS via Pull-up resistor
Switch 2 (Closed to front) CSS to Pin 40??

Does that one wire actually go to pin 40?  That is the odd connection.
Also you state the screen is "brown"

Also what exact pin is the wire connected o on the SN74LS273 IC.

It just seems like a mod that was wired incorrectly.



On Wed, Dec 3, 2014 at 1:11 PM, Camillus Blockx <camillus.b.58 at gmail.com>
wrote:

> For what I can see, I think it the switches are for Inverse video Green on
> black and the second one is for upper and real lowercase characters
> switching.
>
> If you look closely there is a pin lifted out and I think is Pin 39 (CSS)
> and is used for switching character mode.
>
> The bottom switch makes the modification undone by switching the pin 39
> from MC6874P pin to original PCB hole.
>
> The top switch is connected to the SN74LS273, which is a Flip-Flop with
> Clear, but I'm not sure if it is connected to pin 20 of it, which would be
> VCC( 5v) or some other pin. The most likely would be the 5 Volt. I draw
> that conclusion by the black hose in the middle of the wire, in which I
> presume is a resistor (pull up).
>
> This is just guessing of the things I can see on the pictures you provide.
> If you could tell me the exact locations where the modification is done,
> pin numbers, pins lifted out or cut etc..  then I could give you some
> better diagnostics.
>
>  Have coco fun ....
>
> Camillus
> On 12/3/2014 11:45:26 AM, Bruce W. Calkins <brucewcalkins at charter.net>
> wrote:
> ----- Original Message -----
> From: "John Goerzen"
>
> > Hi,
> >
> > So I got a lot of random untested CoCo parts off eBay yesterday. It
> > included a CoCo 2 which seems to have been modified or something. On its
> > left side are two unlabeled switches:
> >
> > https://www.dropbox.com/s/avmph8x7oykd222/coco-switches.jpg?dl=0
> >
> > Anybody seen this before? Any idea what it's about?
> >
> > Thanks,
> >
> > John
> >
> > --
> =======================================
> Manny, many years ago I set up a CoCo 2B with two less obtrusive slide
> switches. One for inverting the boarder video and one for switching the
> lower case/inverted letters. That said, to understand what those switches
> do, you will need to A: trace the wires, and/or B: try them out.
> Bruce W.
>
>
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