[Coco] Back to the COCO

[Bill Gunshannon]

On 1/2/17 8:43 AM, Robert Gault wrote:
> Bill Gunshannon wrote:
>> On 1/1/17 7:44 PM, Robert Gault wrote:
>>> Bill Gunshannon wrote:
>>>> <snip>
>>>> Thanks for the suggestions, some further comments.  Disk drives work on
>>>> other vintage machines and PC's so I don't think it's the drives.
>>>> <snip>
>>> And, as stated, exact same symptom trying to do hard disks using the
>>> Glenside and SCSI controller.
>>>> <snip>
>>>> bill
>>>>
>>>>
>>>>
>>>
>>> Bill,
>>>
>>> Given that your Coco3 works with HDBDOS for Drivewire, the drives work
>>> with other computers, and you have problems with hard drive controllers
>>> on the Coco, the problem would seem to be within the Coco3.
>>> These types of hardware problems are very difficult to handle even for
>>> electronics tinkerers. You can try cleaning the Coco rompack port
>>> connectors but that is a long shot. You will need suggestions from our
>>> hardware experts.
>>>
>>
>> Actually, it may have just become moot.  My 3 has stopped running at
>> all.  No display, nothing but the click of the relay when you power
>> it on.  I have moved some of my testing to a 2 but that isn't where
>> I really want to be so I may be giving up.  I looked on ebay and it
>> looks like COCO3's don't show up there any more at least not in a
>> search.
>>
>> The good news was the SUPERIDE seems to work just fine.  I am DSKINIing
>> 255 virtual disks right now.  I will try putting NitrOS9 on it and see
>> if it works. But that will require finding a version that actually boots
>> on a 2 from Drivewire and I have not found one in any of the stuff that
>> is currently available.
>>
>> If things continue in the direction they seem to be going I may be
>> looking to dump all that I have.  :-(
>>
>> bill
>>
>>
>>
>>
>
> Bill,
>
> Actually your latest symptoms may have simplified the problem. :)
> Now it looks like the power supply in the Coco3 is bad or possibly an IC.
>
> If you have a VOM, a soldering iron, and access to parts, get a copy of
> the Coco3 service manual at:
> http://www.colorcomputerarchive.com/coco/Documents/Manuals/Hardware/Color%20Computer%203%20Service%20Manual%20(Tandy).pdf
>
>
> Look at the schematic on page 103-104 and start measuring voltages in
> the power supply section. A diode or capacitor may have failed. Also
> follow the trouble shooting guide on page 58.
> If the power supply checks out, you may have damaged either the CPU or a
> PIA while plugging units into the ROM socket. That happens if power is
> on or the plugged in device is twisted to short some connectors.
> You may need to replace an IC.

Any chance someone could make a better scan of the schematic and send
it to me?  The one in the PDF is pretty much unreadable.

bill