[Coco] 6309 with a side of half cooked GIME?

[Brian Blake]

I posted this on the
forum<http://tandycoco.com/forum/viewtopic.php?f=6&t=94&sid=f3c091fb43012f6bbea6031cfda3c08d>earlier,
but, it's nowhere near as heavily traveled as the mailing list.

I attempted the 6309/6809 piggyback install as posted on
coco3.com<http://www.coco3.com/community/2011/03/piggyback-6309-upgrade>.
I chose the switch method, and added LED's so I could tell at a glance which
CPU was active, that info is
here<http://tandycoco.com/forum/viewtopic.php?f=48&t=87&sid=f3c091fb43012f6bbea6031cfda3c08d>
.

One of the referenced links tells the complete story, but, it failed. At
boot, the monitor displayed weird colored glyphs on the screen.

I looked over the issue with my 'piggyback' attempt. It appears I somehow
pooled some solder between pins 21 & 22 (A12 & A13) on the 6809 when I
soldered the socket on - I know I tested for continuity between pins before
turning the computer on, but, I may have missed these pins. When I turned
the CoCo3 on, all I would get was weird patterns and glyphs on the screen.
What's the potential for damage to other IC's? After removing the
6809/socket, cleaning everything up and soldering a fresh socket, I have a
normal boot screen, but, lack any real stability.

Typing in the following:

10 ?"HELLO WORLD"
20 GOTO10
RUN

...will give the expected results for about 10 seconds. Then it usually
fails with a SN or FC error. In fact, I can turn on the CoCo3 and just leave
it alone. After 2-3 minutes the screen goes all wonky without user
interaction at all. The only two IC's I see, besides the CPU, that get all
address lines is the GIME and U2. I did a continuity check between all of
the address lines from the CPU to different IC's and connection on the
motherboard and all check out okay, so I think it's down to a bad IC - none
of which seem overly hot to the touch, or even warm when the failure occurs.
Any suggestions?

Also, this CoCo has a DP Johnson 512k upgrade installed. I noticed the two
caps that normally are clipped during a 512k upgrade have not been clipped -
doubt this is related, but...





-- 
Ohioan by birth, Floridian by the grace of U-Haul and a bad economy...