[Coco] Weird CoCo3 problem - AAAARRRGGGGGHHHHH!!!!

[Christopher Hawks]

Brian Blake said the following on 01/03/2010 03:35 PM:
> The latest;
> 
> Upon further testing, R22 was not doing anything. The solder pad on the bottom of the mobo was broke, an the leg on the end that's supposed to connect to C65 had been lifted. I took R22 completely out and replaced it with a new 120-ohm resistor. Then I took a short piece (3/16 - 1/4") of speaker wire and soldered it to the leg of R22 that is supposed to go to pin 4 of the GIME, scraped away some green stuff and soldered the other end directly to the trace. Continuity restored. Continuity from R23 was fine. Cleaned up the solder pads from where I clipped out the 6809, soldered in the socket, installed the 6309 and put everything back together. Turn her on and was greeted with the 'Extended Color Basic....yada, yada' greeting, okay that worked. Tried Tetris, S/S Pak and O-90, all worked as expected. Still have the same problem with the FD-502; POKE &HFF40,1 does not turn on the drive light, and any disk commands end up with an I/O? error with no activity
>  being present on the drives when the commands are issued... AAAARRRGGGGGHHHHH!!!!
> 
> I went to R/S today only to find out they no longer carry a logic probe, so I'm stuck with using my DMM for now. When issuing a POKE &HFF40,1 in a loop, IC9 pin 6 is 'HI' on the DMM in logic mode, but, in frequency mode it shows up as a 192.5-kHz signal. Pin 36 of the 40 pin connector shows the same results. Other than evidently ruining a perfectly good 6809, so far the only thing I've accomplished is completing a 6309 swap on a CoCo3 with 'floppy phobia'... So, I'm still open for suggestions. Tomorrow I'll be bringing home my 50-MHz scope so I'll at least be able to look at waveforms. At this point,based on my limited knowledge and materials I'm looking at, I'm leaning towards replacing IC9 to see if that helps, but, I'd rather not start chip swapping just for the heck of it, so PLEASE, if you guys who are far more knowledgeable than I have any suggestions, I'm listening!!!

Brian:

	The Speech/Sound Pak (and I think the Orchestra Pak) are self-decoding. They 
don't use Pin 36 <SCS>.

	Pin 6 of IC 9 connects to Pin 40 of the cartridge slot <SLENB> (and is pulled 
Hi). Pin 9 of IC 9 connects to Pin 36 <SCS> of the cartridge slot. If Pin 36 
doesn't change, Pin 9 of IC probably isn't either. IC 9 must be at least partly 
working since the internal ROM, Disk ROM, and PIAs are selected correctly (pins 
15, 14, and 13). If you check these Pins, be aware that the ROM selects will 
only be active at startup when the ROMs are copied to RAM. You could also check 
IC 9 Pins 1, 2, and 3. These are the Pins that the GIME drives to select the 
outputs of IC 9. According to IC 9's datasheet Pin 9 will be low when Pin 1 is 
low and Pins 2 and 3 are high. You should see Pin 3 pulsing during the Poke.

-- 
Christopher R. Hawks
HAWKSoft
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