[Coco] Back to the COCO

[Robert Gault]

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.

Robert