Well, anybody who followed this thread on the mailing list has an idea of the problem with this CoCo3. It seemed to have a fear of floppy drives. After all of the troubleshooting (including a couple miscues by yours truly) we thought we had it pegged to the 74LS138 chip, aka IC9. So, I placed an order with Jameco last Friday for a replacement (and the IC's to build an MPI, that's another story), and that order landed yesterday.
This morning, after my wife went to work, I clipped the 138 off of the motherboard, cleaned the holes and soldered a socket in the chip's place. After cleaning everything up, I inserted the chip, hooked the mobo back up inside the CoCo3 case, made the necessary connections and powered it on. And it worked!!! The two pics below show the floppy light on drive 1 doing a 'DIR' command and loading Sockmaster's Donkey Kong conversion.
Below is the loading screen (for those living under a rock since 2007) of DK. Note the little beige and grey box with lit green LED - Roy Justice's VGA adapter. If you don't have one, buy one. It does not disappoint!!!
The pic below shows the socketed 6309 and 74LS138 chip.
All in all it was a fun learning experience. Anytime I come away from a situation like this and have learned something, I'm happy. Incidentally, how hot should the heat-sink get for Q1? After about half an hour of Donkey Kong, that thing was hot!! I'm thinking about yanking the PS off of this one and using a 90w ATX unit or some other type, maybe something like theotherBob had posted on his now defunct GeoCities page... just for giggles. My repack is powered by a 200w ATX that runs everything except the LCD (which runs off of it's own PS tapped from the 120vac plug the ATX unit runs from), so I think 90w for the CoCo and maybe an internal 3.5" floppy would be fine.
Later,
MCCM
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