[Coco] Coco SDC troubleshooting: no ROM found

[Zippster]

Great!

- Ed


> On Nov 28, 2014, at 6:45 PM, Richard Goedeken <Richard at fascinationsoftware.com> wrote:
> 
> Thanks for the tips, to everyone who replied.  After more troubleshooting, I
> found that one of the pins on the PLCC32 socket for the flash rom chip was
> bent, and it was short-circuiting against the pin next to it.  This had the
> unfortunate effect of grounding D2.  After straightening the pin and
> reinstalling the flash chip, it works great!
> 
> Thanks,
> Richard
> 
> On 11/28/2014 07:26 AM, Darren A wrote:
>> On Thu, Nov 27, 2014 at 11:36 PM, Richard Goedeken wrote:
>> 
>>> Hello everyone,
>>> 
>>> Today I built up two CocoSDCs from kits, and one of them works perfectly
>>> but
>>> the other does not.  If anyone could help me get my second unit working I'd
>>> much appreciate it.
>>> 
>>> The non-working unit doesn't boot up with the SDC-DOS extensions.  It just
>>> boots as Extended Color Basic 2.0 or whatever the default Coco3 basic ROM
>>> is.
>>> The LED will light up and stay lit if there's no SDHC card inserted at
>>> power
>>> up.  If there is a card plugged in however, the LED will light for a
>>> second or
>>> so after power-on, and then it will turn off.  It flashes if I hit reset.
>>> So
>>> some portions of the system are working.  But for some reason the Coco
>>> doesn't
>>> start up the SDC-DOS rom extension, so it is not usable.
>>> 
>> 
>> <snip>
>> 
>> Richard,
>> 
>> You may want to PEEK the first few locations starting at $C000 (49152). The
>> first two bytes of the ROM image should be the ASCII characters 'DK'. If
>> one or more of the data lines has a contact problem then this may reveal it.
>> 
>> There is a schematic available for download from the blog site. You could
>> check for CE* and OE* continuity between the pins of the CPLD and Flash
>> chips along with the bank addressing lines.
>> 
>> Darren
>> 
> 
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