[Coco] CoCo Model 1 Cartridge Port

[Charles Hudson]

Disassembled the drive until I could move the positioning stepper by 
hand; I've never seen a mechanism like that before, must be particular 
to TEC drives.  But I moved it back and forth enough to feel that it was 
free and see that the track 0 switch was operating.  I cleaned the index 
LED and reflowed a couple of capacitors on the board and made sure the 
plugs were making good contact, then reassembled.

With the cover still off I connected the drive to my SuperCard Pro 
(attached to a Win10/64 machine) and ran a couple of  tests: The SCP 
recognized the drive as D1; the maximum track test stepped out to 87, 
according to the SCP, but the drive speed test did not report anything.  
Hmmm...

On the drive circuit board I noticed a terminating resistor and a jumper 
with options A | B.  The jumper was set to B, so I moved it to A and 
repeated the SCP tests.  This time the SCP recognized the drive as D0 
and the speed test reported 300.x RPM.

I buttoned up and reconnected to the CoCo, using the middle connector at 
the drive.  The dskini0 ran, without lighting the drive light, and I 
counted 34 steps.  But the process ended in IO ERROR again.  Turning 
everything off I switched to the end plug, powered up and repeated the 
initialization procedure.  This time the drive light was on.  I counted 
34 steps again and then the drive backed up to track zero and verified 
the initialization.  At the end of the process I got the OK prompt with 
no errors.  Bonus!

Thank you all for your help:  It has (literally) taken me years and many 
dollars to get to this point, but here I am at last.  Now I just have to 
figure out how to get Internet files onto disks that the drive can read.

-CH-

On 12/24/2021 11:02 AM, Rick Ulland wrote:
>
> On 12/24/21 8:48 AM, Charles Hudson wrote:
>> Following your advice I moved the cable to the last connector (on the 
>> end with two connectors) and repeated the process of "dksini0".  This 
>> time the drive light came on and I could hear the stepper motor move 
>> the head.  I failed to count the steps - I was completely surprised - 
>> but a dozen steps or more activity ceased and the light went out.  
>> The result on the screen once again stated IO ERROR.
>>
>> I then tried repeating the disk format.  This time I heard the 
>> mechanism straining; no regular repeated stepping and after a few 
>> steps with long pauses between them the activity ceased and I got 
>> another IO ERROR message.
>>
> I'd bet dollars to donuts Art is correct. The way a CoCo drive is 
> supposed to work, you turn it own. The head position is unknown. First 
> operation steps the head a whole buncha times, to make sure it's 
> banged against the end stop for a while. DECB still doesn't know the 
> head position, but assumes surely this is 0 and counts from here until 
> death. If the head doesn't move, or doesn't move properly, DECB 
> doesn't know and forges ahead until there is a read error.
>
> Pop the top, watch the show. Bring hair clipper oil for the dry slide 
> rails. And Merry Christmas.
>
> -ricku
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