[Coco] CoCo 1 troubles

[Rick Ulland]

It sounds like the recap is, there are two select methods at work. The 
cable normally has 4 physical drive select pins. DECB calls this 4 
single sided drives, OS9 (and IBM) calls this 3 drives + side select. 
Anyway, with a straight through cable with all pins in place, any drive 
can be jumped to look at cable select 0 or 1, and double sided drives 
will look to the fourth select pin as a side select.

That was deemed too hard for the masses so two workarounds were adopted. 
Tandy jumpered each drive to 'I am both sides of all the drives', and 
pulled the competing select fingers from each cable socket. PC jumpered 
all drives to the same number and flipped a few wires to allow a pair of 
DS floppies. Did they set each drive to 1? That would allow aftermarket 
drives (setup as a second unit) to drop into any position.

Anyway, if your drive is jumpered to be drive one, it will work on a 
Tandy connector that does not have it's drive one pin pulled out, but it 
will not work on any other Tandy connector because it is ONLY looking 
for the drive one select. It should be looking for any drive select that 
hasn't been ripped out by the roots, or (less good) looking for drive 0 
select, then it will break if moved back to connector one.

I agree the bad format is very likely hardened grease on the metal rails 
the head slides on, or fuzz bunnies blocking travel to the end stops. Or 
a crappy belt, if these be old Tandons with a drive belt.

-rick



On 12/24/20 3:16 PM, Gene Heskett wrote:
> On Thursday 24 December 2020 12:43:00 Salvador Garcia via Coco wrote:
>
>>   Yes, totally agree. The only problem is that when I connect it to the
>> cable's drive 0 connector, the LED does not light at all and the drive
>> is not recognized. The motor spins up though, but that is all.
>>
>> Currently, I believe I have two problems:
>>
>> 1. Drive 0 is not recognized
>> 2. Drive 1, while recognized, is still giving IO ERRORs
>>
> Its sounding as if that drive is not programmed to be drive one, which
> would make the twisted cable work, but as some other drive, selectable
> by jumpering the drive address wanted with a flea clip moved from ds0 to
> ds2. You'll find that on 5.25" drives but the 3.5"ers generally had a
> solder blob connecting the #1 PCB dots, look carefully.
>
> But DS3 isn't available for OS9/Nitros9 because its miss-labled. its
> actually the side signal that OS9 uses to access double sided drives.
>
> In that event replace any connectors on the drive cable that are missing
> teeth, with fully equipted connectors and do away with the twist. I
> usually just replaced the whole cable with new as it wasn't the best
> quality of cable to start with.
>
> Then the drive will be same drive # regardless of where it is on the
> cable.
>
> And remember that the resistor packs that plug into a 14 pin dip socket
> on the drive board, are only installed in the last drive on the far END
> of the cable.  It is not all that fast, but that cable IS in fact a
> transmission line that MUST be terminated at both ends.
>
>> My next steps are:
>>
>> a. Try with a different floppy to see if that makes any difference
>> while testing drive 1
>> b. Follow Bill P's advice and clean the heads
>> c. Swap cables. Barry Nelson provided information on how to make this
>> cable, even providing references to the parts needed
>> d. Possibly test
>> the speed using the flourescent lamp method already suggested (I say
>> possibly because I don't have a flourescent light here)
>>
>> Thank you for your continued help. It is much appreciated! Salvador
>>
>>
>>
>>
>>
>>      El miércoles, 23 de diciembre de 2020 07:08:52 p. m. CST, Arthur
>> Flexser <flexser at fiu.edu> escribió:
>>
>>   If the drive is regarded as Drive 1 as you have it currently
>> connected, it seems like it should be regarded as Drive 0 if you plug
>> it into the other drive connector on the cable.
>>
>> Art
>>
>> On Wed, Dec 23, 2020 at 7:11 PM Salvador Garcia via Coco <
>>
>> coco at maltedmedia.com> wrote:
>>>    Thanks again, much appreciated!
>>>
>>> I see the socket. It is populated. It looks like a white IC, stamped
>>> "Beckman". Most certainly that's the resistor pack.
> Yes.
>
>>> Nope, DSKINI 1 it is. Trying to access drive 0 does nothing, only
>>> the motors spin up then the IO ERROR.
>>>
>>> DSKINI 1 starts the formatting process and after stepping 34 times
>>> and doing a seek, I get IO ERROR.
>>>
>>> Yes, looking straight into the drive connector I see some dark
>>> areas. That's probably where the pins are missing.
>>>
>>> I can not access files on an already formatted diskette
>>>
>>> Salvador
>>>
>>>
>>>
>>>
>>>      El miércoles, 23 de diciembre de 2020 04:29:14 p. m. CST, Arthur
>>> Flexser <flexser at fiu.edu> escribió:
>>>
>>>    On some systems, especially those Tandy initially sold for the CoCo
>>> 1, drive selection is done by having pulled pins on the different
>>> cable connectors, rather than by jumpers within the drives.  If you
>>> look at the cable connectors end-on, you should see different pins
>>> pulled on the different connectors.  You should still have a
>>> terminating resistor in the last drive in line.  Is there a
>>> prominent empty socket within the disk drive that looks like a
>>> resistor might go there?
>>>
>>> Do you mean DSKINI1, not DSKINI0?  Ordinarily, with just one drive,
>>> that one would be Drive 0.  That DSKINI gets through 34 steps and
>>> then bombs means that correct formatting did not take place, in that
>>> DSKINI has gone back to Track 0 and begun its verify pass, trying
>>> without success to read from the just-formatted tracks
>>>
>>> Can you access files on an existing, already formatted disk with
>>> data on it?
>>>
>>> Art
>>>
>>>
>>>
>>> --
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>>> Coco at maltedmedia.com
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>> --
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>
> Cheers, Gene Heskett