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

[Bob Devries]

Brian,
just be sure that your DMM is not picking up hash from the computer in 
frequency mode.

Maybe the following code would be batter:

10 POKE &HFF40,1:REM SELECT DRIVE 0
20 FOR X=1 TO 1000:NEXT X:REM TIME DELAY
30 POKE &HFF40,0:REM DESELECT DRIVE 0
40 FOR X=1 TO 1000:NEXT X:REM TIME DELAY
50 GOTO 10:REM LOOP

Adjust the for-next loop to your personal tastes :)

Having found one broken trace at R22, you may need to recheck other pads for 
broken traces.

Regards, Bob Devries
Goulburn, NSW, Australia

--
Besides a mathematical inclination, an exceptionally good mastery of one's 
native tongue is the most vital asset of a competent programmer.

Edsger W.Dijkstra, 18 June 1975

----- Original Message ----- 
From: "Brian Blake" <random_rodder at yahoo.com>
To: "CoCoList for Color Computer Enthusiasts" <coco at maltedmedia.com>
Sent: Monday, January 04, 2010 8:35 AM
Subject: Re: [Coco] Weird CoCo3 problem - AAAARRRGGGGGHHHHH!!!!



> 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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