[Coco] CoCo floppy disk subsystem

[Gene Heskett]

On Friday 15 January 2021 13:26:09 Salvador Garcia via Coco wrote:

>  I took a quick and dirty pic of the controller with my Web cam:
>
> https://drive.google.com/file/d/12qXDKO4ry3tdBFFqU5mz-ADVi2c384pn/view
>?usp=sharing
>
>
> Although a bit blurry, the three pots are prominently visible at the
> top of the PCB. 
>
> If I were to swap out the controller for an FD501 or 502, will these
> controllers work with the floppy drive that came with my 26-3022
> system? Thanks! Salvador
>
>
>
>     On Friday, January 15, 2021, 08:23:26 AM CST, Rick Ulland
> <rickulland1 at gmail.com> wrote:
>
> On 1/14/21 6:19 PM, Salvador Garcia via Coco wrote:
> >  I have heard about the WD1793's lack of reliability.
> > Would swapping out the WD1793 with an MB8877A help eliminate
> > reliability issues? Thanks, Salvador
>
> If this is the original controller with three adjustment pots inside,
> that's the infamous analog data separator. I believe the 12v is to
> power this bit. Bound to be off by now, and I think you need a test
> disk to get it back on. Has value as a cool part, but maybe not
> practical.
>
The test disk might be handy but it MUST BE an original Dyson disk, 
copies need not apply as they will NOT contain the errors the original 
has.

But a decent scope will suffice for the pot adjustments, you'll want to 
see in the output pattern a 50% duty cycle between logic 0's and logic 
ones. Very easy to see with a triggered scope. Not very easy on an 80 
dollar ebay model.
>
> -ricku


Cheers, Gene Heskett
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