[Coco] 26-3022 Disk Controller Question

[Arthur Flexser]

Now that I recollect further, Gene, I recall that I wasn't the slightest
concerned about and only vaguely even aware at the time I needed to replace
my 1793 chip that the 1793 required 12 volts rather than 5.  Back then,
only the CoCo 1 existed, and only the initial 26-3022 controller, so the
distinction wasn't relevant at all to me.  I think I actually ordered the
WD1793 from someplace like Jameco and unexpectedly received the Fujitsu
8877A instead, which served as an adequate replacement, so I had no
complaints.

It was only a couple of years later, after I acquired a CoCo 2, that I
found my 26-3022 controller worked just fine with it, and wondered what the
fuss was about. After a bit of thought, I remembered that I had replaced
the controller chip a couple of years before with the Fujitsu version and
went "aha!"

Art

On Sun, Sep 3, 2017 at 1:56 AM, Gene Heskett <gheskett at shentel.net> wrote:

> On Sunday 03 September 2017 00:01:43 Arthur Flexser wrote:
>
> > I believe replacing the 1793 with an 8877A does work as you describe,
> > and I'm almost sure it worked for me that way, long ago.  As I recall,
> > I discovered this fact accidentally, having replaced with the Fujitsu
> > chip because I couldn't find a 1793.
> >
> > Art
>
> That is correct Art, the MB8877A does not need that funkity 12 volt
> adjustable bias circuit the WD1793 needed. I have a data sheet on the
> MB8877A around someplace in this midden heap, and IIRC, there is a B
> model that can run at 2x the clock and with some switching tom-foolery,
> should be able to make use of 1.44 megabyte drives as true 1.44 megabyte
> drives. But by the time I became aware of that, I had already setup a
> Maxtor 7120s 132 meg hard drive on a disto 4n1. All history now.
> >
> > On Sat, Sep 2, 2017 at 11:26 PM, Garrett Reynolds
> > <greynolds86 at hotmail.com>
> >
> > wrote:
> > > I picked up a Drive 0 1st generation (grey) single floppy drive and
> > > controller.  The original label is missing but I assume this is the
> > > 26-3022 as it is equipped with the WE FD1793B-02.  I understand this
> > > controller is not very popular or reliable.  I've read that it will
> > > not work on the CoCo2/3 (I have a CoCO3).  I believe this is because
> > > it needs 12VDC to function which is not present on the later
> > > computers or needed by the newer controllers (that's weird to say,
> > > "newer controllers").
> > >
> > > Anyway, I've read that if you replace this DIP CHIP with a Fujitsu
> > > MB8877A that it will then work with the CoCo2/3.  I found several of
> > > these chipsets on ebay for around $10.  Does anyone have experience
> > > with this controller, the modification that I speak of and any
> > > recommendations as to making this controller work with my CoCo3?
> > >
> > > I did open the controller, seat the components, and cleaned up the
> > > pins and confirmed that controller boots to DECB.  I did not attempt
> > > to plug in the drive or access it pending answers to these
> > > questions.
> > >
> > > I also read that if you have a multi-pak that this controller will
> > > work without modification, but I do not have one.
> > >
> > > Your ideas/suggestions are graciously invited.
> > >
> > > Garrett
> > >
> > > --
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> > > Coco at maltedmedia.com
> > > https://pairlist5.pair.net/mailman/listinfo/coco
>
>
> Cheers, Gene Heskett
> --
> "There are four boxes to be used in defense of liberty:
>  soap, ballot, jury, and ammo. Please use in that order."
> -Ed Howdershelt (Author)
> Genes Web page <http://geneslinuxbox.net:6309/gene>
>
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