[Coco] Broken CC3

[Gene Heskett]

On Friday 12 September 2008, George Ramsower wrote:

>>>>> On Friday 12 September 2008, George Ramsower wrote:

>>>>>>Darn,

>>>>>>

>>>>>> My CNC coco broke.

>>>>>>

>>>>>> It starts up and displays the usual stuff. I can ?mem and it reports

>>>>>>correctly. However, when I boot OS9, it crashes.

>>>>>>

>>>>>> I appears to crash when it loads the first boot sector.

>>>>>>

>>>>>>I tried other boot disks with the same results.

>>>>>>I replaced the CPU, RAM board, reseated the GIME, polished the edge

>>>>>>connector on the disk controller, reseated the ROM in the controller

>>>>>>and

>>>>>>all gives the same results.

>>>>>>

>>>>>> Suggestions?

>>

>> Does anyone remember why we modified the circuit at IC-9 to add a 74LS02?

>>

>> I'll try another '02 there, since it's socketed.

>

> This is interesting. The added chip on a spare CC3 board is an '02 but on

>the CNC coco it's an '04 chip. Since the latter was working, I'll have to

>assume it was supposed to be an '04.

>I put another one in that socket and the CC3 is still broken.

>

Humm, the 'ls02 is a quad NOR gate, the 'ls04 is a hex inverter.  That is not 
generally interchangeable.

>

>--

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-- 
Cheers, Gene
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