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

[John Donaldson]

Brian,
   I am a Software and Network Engineer by trade and also done a bit of 
call center work too. So I was trying to cover all the angles because 
you be surprised how simple things can get past you. Looking at all the 
responses now, I can see it narrowing down to either a missing control 
or interrupt signal that is not getting to the controller. Since you do 
see the DOS ROM, this in itself eliminates a lot of signals. Also if you 
put a ROM pack in and it auto starts it, then the main interrupt seems 
to be OK.

OK gang we can eliminate the Disk ROM, Address Lines ,Data Lines, and 
CART line. What is left that can cause a drive not to respond?

John Donaldson



Brian Blake wrote:
> Hi John,
>
> When I posted that, it meant that I had not inserted the FDC at that point. I was unclear on that I guess. When I insert the controller, I get the 'Disk Extended...' screen as one would expect. I just get no response from the disk system when disk commands are issued - and yes, the drive is powered on, lol. This is the most perplexing issue I've run into in a long time...
>
> I've had to put it to the side for a bit since I have a client's server I'm working on right now. I'll be getting back to it tomorrow afternoon, hopefully my head will have cleared and a few other guys will pop in with ideas of where to look. 
>
>
>
> ________________________________
> From: John Donaldson <johnadonaldson at sbcglobal.net>
> To: CoCoList for Color Computer Enthusiasts <coco at maltedmedia.com>
> Sent: Sun, January 3, 2010 9:17:57 PM
> Subject: Re: [Coco] Weird CoCo3 problem - AAAARRRGGGGGHHHHH!!!!
>
> Brian,
>    I think I see one big problem right now. You said
>
> Turn her on and was greeted with the 'Extended Color Basic....yada,
>
> If you had the controller installed you should have gotten "DISK EXTENDED BASIC" or something like that that tells you that the DSIK ROM has been read and is operating. This may explain why all the DISK commands give I/O error since the DOS is not present. Look at what is displayed when you put the controller in another good system, then look at the display when the controller is in the system that does not work.
>
> Either something like this is going on or I am mi-reading your posts.
>
> John Donaldson
>
>
>
> Brian Blake wrote:
>   
>> 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!!!
>>
>>
>> Thanks,
>>
>> Brian
>>
>>
>>      
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>
>
>   


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