[Coco] CoCo Disk Drives

[Rick Thornquist]

Al and Gene -

All right, I opened the drives up.  Even though they have different catalog
numbers, they appear to be pretty much identical on the inside (then again,
the catalog number on the 26-1164 is on a sticker over the previous one -
I'll have to see what's under there someday).  Even the drive mechanism -
Texas Peripherals (10-5355-001) - is the same.  Texas Peripherals?  Hmm...
Doesn't sound quite legit. :)

Anyway, here's a picture of the logic board of the 26-3029:

https://dl.dropboxusercontent.com/u/18477511/26-3029%20Logic%20Board.jpg

There doesn't appear to be any DIP switches or jumpers for drive select,
instead there appear to be four drive select lines in the bottom right or
the logic board - DS 1 2 3 4.  I guess they expect you to do the drive
selection with a pulled pin cable.  Fine with me.

As far as the termination pack is concerned, I'm thinking that it's R51,
right above the drive select lines.  It has six pins.  Please correct me if
I'm wrong!  Both drives have this pack so it seems like I have to remove
one of them.

Here's the thing.  The pulled pin cable is set for drive 0 in the middle of
the cable and drive 1 at the end.  You all are saying that the termination
pack should only in the drive at the end of the cable, so that will be
drive 1.   That also sound good, but Service Manual that I found says on
page 5 (page 8 of the PDF), "The Resistor TerminatIon in the IC socket is
used in Drive number zero only. It must be removed for Drives one. two and
three."  But my drive 0 is in the middle of the cable!

Here's the Service Manual:

https://dl.dropboxusercontent.com/u/18477511/Radio%20Shack%20Mini%20Disk%20Service%20Manual.pdf

So, where should the terminator be, on drive 0 (like the manual says) or
drive 1 (at the end of the cable)?

- Rick

On Fri, Feb 27, 2015 at 12:05 PM, Gene Heskett <gheskett at wdtv.com> wrote:

>
>
> On Friday 27 February 2015 09:21:00 Rick Thornquist wrote:
> > Since you guys were so great answering my previous question, I have
> another
> > for you.
> >
> > When I acquired my CoCo 3, I got a 26-3029 controller and two disk
> drives,
> > a 26-3029 and a 26-1164.  I didn't get any manuals, so I just connected
> > them up in what looked to be the right way.  I have the 26-3029 connected
> > to the middle of the floppy cable (as drive 0), and the 26-1164 connected
> > to the end of the cable (as drive 1).  The setup does work for the most
> > part, but there is some flakiness, mainly with the 26-1164.
> >
> > My question: Is there some configuration, like with drive select dip
> > switches or terminators, that I'm supposed to do?  Also, my Internet
> > digging suggests that the 26-1164 is a TRS-80 disk drive - is it also
> > supposed to work with the CoCo?  .
> >
> > Thanks!
> >
> > - Rick
>
> Two things to pay attention to, Rick.
>
> 1. Only the drive connected at the end of the cable is supposed to have
> resistor packs installed to terminate the lines.  If both have them
> installed, thats too much of a load on the controller.  If none are
> installed
> (empty 8 or 9 pin inline sockets) then you have to find a set and install
> them
> on the end drives pcb.
>
> 2. Generally speaking, MOST of these drives have a means of selecting which
> drive address they respond to, and because the default cable supplied by
> the
> shack actually does that with missing "teeth" in the edge connectors on the
> cable, and intend that the drive on the end of the cable is drive 0, I
> usually ditch those connectors and crimp on 34 pin card edge socket
> connectors that are fully populated so you can actually make use of the DS
> jumpers on the drives board, s/b 4 choices in 5.25" drives but only 2 on
> the
> 3.5"ers. One and only 1 position is jumpered in this case.
>
> However you jumper them, its the end of the cable drive only that needs the
> terminations installed.
>
> No clue what the 26-1164 drive is, single head or double sided heads, but
> its
> likely that at that age, completely usable on the coco's, at least with
> os9/nitros9 when the descriptor is configured to match what the drive can
> do.
>
> 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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