[Coco] Disk controller

[Bob Devries]

Gene,

as far as I know, the 3.5"drives all had 1k ohm resistors as 
terminators, and thus don't need to have the resistors removed. 
5.25"drives mostly had 150 ohm resistors.
I have never found a need to remove resistor packs except on 5.25"units, 
and 3.5"co-exist happily with them.

Regards, Bob Devries
Dalby, QLD, Australia

On 16/04/2014 10:26 AM, Gene Heskett wrote:
> On Tuesday 15 April 2014 20:20:58 Chad H did opine:
>
>> Well, not sure if those controllers have 7416 buffer chips or not, but
>> one of my FD-502 controllers was acting erratic and after desoldering
>> the 7416's and replacing them with beefier 7406 buffer chips it was
>> good as new.  I went ahead and did the upgrade to my other controller
>> to. Have never since had any further problems out of either one.  This
>> might be something to check IF it has the 7416 chips..
>>
>> http://www.mediafire.com/view/cde2vmcqp63jt/Board%20Images#4sqrj7b4u1qpp
>> 5q
>>
>>
>>
>> -----Original Message-----
>> From: coco-bounces at maltedmedia.com [mailto:coco-bounces at maltedmedia.com]
>> On Behalf Of Bill Pierce Sent: Thursday, March 27, 2014 10:17 AM
>> To: coco at maltedmedia.com
>> Subject: Re: [Coco] Disk controller
>>
>>
>> Gene, that was going to be my reply :-P
>> I spent about 3 days one time trying to figure out why my drive wasn't
>> working. I had moved my system from one room to another and went from a
>> working system to a drive coming on and nothing else happening. I don't
>> remember why I tried flipping the cable, but that what I ended up
>> doing. When that solved te problem, I then marked the top side of the
>> cable on both ends to make sure that didn't happen again. As a note,
>> most 3.5 drive cables can't be flipped as they have a guide pin, but on
>> a Coco, the initial cable is usually terminated with the (then)
>> standard 5.25 type ends. There's usually an adapter from 5.25 style to
>> 3.5 style at the drive end of the cable. In my setup, it is actually
>> inside the case on the adapter plate. It has a "single drive" cable
>> running from the controller to the drive case. The cable then plugs
>> into a "card edge" on the back of the drive case (3rd party, not Tandy)
>> with 5.25 style connection, then continues via ribbon cable inside with
>> 2x 5.25 style connectors to the adapter plate which also has a 5.25
>> card edge built in that goes to a very short 3.5 style cable that
>> connects to the drive. Talk about a hassle to clean all the card edges,
>> 4 in all from the Coco to the drive. 5 if I use a second 3.5 drive.
>>
>> I also have several "hybrid" cables that have 5.25 style connectors as
>> well as 3.5 style. All my 3.5 drives have drive select jumpers so I can
>> use them in any order I want.
>>
>>
>> Bill Pierce
> However, ONLY the last drive in the chain is to have the terminating
> resistor packs installed, or, in the case of the 3.5's, one might have to
> get a glass and read the artwork on the pcb to find the cut or bridge
> jumper that controls that.  And in my dumpster diving I have yet to find a
> 3.5" drive that was switch selectable.  Occasionally one might be
> selectable via solder blob bridges, so you are lucky in that regard.  What
> make & model are yours, so I can be on the lookout?
>
> Cheers, Gene