[Coco] CoCo Disk Drives

[Al Hartman]

Rick,

Texas Peripherals was a cooperative venture between Tandy and Tandon to 
manufacture disk drives. These drives are cost reduced versions of the 
Tandon TM-100-1 floppy drive.

The 8 pads connected by traces are your drive selects. If you notice, all 
four are connected and unbroken.

R51 is your Termination Resistor.

Termination has to be in the last drive on the cable (usually drive 0 is the 
last connector, but someone made up your cable differently), so in your case 
that would be drive 1. Take the one out of drive 0, and tape it somewhere 
secure inside the drive so you can use it again if need be.

-[ Al ]-

-----Original Message----- 
From: 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